Measurement of the Soft-Drop Jet Mass in pp Collisions at s=13  TeV with the ATLAS Detector

2018

Jet substructure observables have significantly extended the search program for physics beyond the standard model at the Large Hadron Collider. The state-of-the-art tools have been motivated by the ...

Search for a Standard Model Higgs Boson inWH→ℓvbb¯inpp¯Collisions ats=1.96  TeV

2009

We present a search for a standard model Higgs boson produced in association with a W boson using 2.7 fb(-1) of integrated luminosity of pp collision data taken at square root s = 1.96 TeV. Limits on the Higgs boson production rate are obtained for masses between 100 and 150 GeV/c(2). Through the use of multivariate techniques, the analysis achieves an observed (expected) 95% confidence level upper limit of 5.6 (4.8) times the theoretically expected production cross section for a standard model Higgs boson with a mass of 115 GeV/c(2).

Search for the Higgs Boson in theH→WW(*)→l+νl−ν¯Decay Channel inppCollisions ats=7  TeVwith the ATLAS Detector

2012

A search for the Higgs boson has been performed in the H -> WW(*()) -> l+vl-(v) over bar channel (l = e/mu) with an integrated luminosity of 2.05 fb(-1) of pp collisions at root s = 7 TeV collected with the ATLAS detector at the Large Hadron Collider. No significant excess of events over the expected background is observed and limits on the Higgs boson production cross section are derived for a Higgs boson mass in the range 110 GeV< m(H) < 300 GeV. The observations exclude the presence of a standard model Higgs boson with a mass 145 < m(H) < 206 GeV at 95% confidence level.

Search for new phenomena in the WW→lνl′ν′ final state in pp collisions at s=7TeV with the ATLAS detector

2013

This Letter reports a search for a heavy particle that decays to WW using events produced in pp collisions at root s = 7 TeV. The data were recorded in 2011 by the ATLAS detector and correspond to an integrated luminosity of 4.7 fb(-1). WW -> lvl'v' (l,l' = e or mu) final states are considered and the distribution of the transverse mass of the W W candidates is found to be consistent with Standard Model expectations. Upper limits on the production cross section times branching ratio into W boson pairs are set for Randall-Sundrum and bulk Randall-Sundrum gravitons, which result in observed 95% CL lower limits on the masses of the two particles of 1.23 TeV and 0.84 TeV, respectively.

Search for contact interactions and large extra dimensions in dilepton events fromppcollisions ats=7  TeVwith the ATLAS detector

2013

A search for nonresonant new phenomena, originating from either contact interactions or large extra spatial dimensions, has been carried out using events with two isolated electrons or muons. These events, produced at the LHC in proton-proton collisions at root s = 7 TeV, were recorded by the ATLAS detector. The data sample, collected throughout 2011, corresponds to an integrated luminosity of 4.9 and 5.0 fb(-1) in the e(+)e(-) and mu(+)mu(-) channels, respectively. No significant deviations from the Standard Model expectation are observed. Using a Bayesian approach, 95% confidence level lower limits ranging from 9.0 to 13.9 TeV are placed on the energy scale of llqq contact interactions in…

Performance of jet substructure techniques for large-$R$ jets in proton-proton collisions at $\sqrt{s}$ = 7 TeV using the ATLAS detector

2013

This paper presents the application of a variety of techniques to study jet substructure. The performance of various modified jet algorithms, or jet grooming techniques, for several jet types and event topologies is investigated for jets with transverse momentum larger than 300 GeV. Properties of jets subjected to the mass-drop filtering, trimming, and pruning algorithms are found to have a reduced sensitivity to multiple proton-proton interactions, are more stable at high luminosity and improve the physics potential of searches for heavy boosted objects. Studies of the expected discrimination power of jet mass and jet substructure observables in searches for new physics are also presented.…

Search for Standard Model Higgs Boson Production in Association with a W Boson at CDF

2012

We present a search for the standard model Higgs boson production in association with a W boson in proton-antiproton collisions (pp̅ →W±H→ℓνbb̅ ) at a center of mass energy of 1.96 TeV. The search employs data collected with the CDF II detector which correspond to an integrated luminosity of approximately 2.7  fb-1. We recorded this data with two kinds of triggers. The first kind required high-pT charged leptons and the second required both missing transverse energy and jets. The search selects events consistent with a signature of a single lepton (e±/μ±), missing transverse energy, and two jets. Jets corresponding to bottom quarks are identified with a secondary vertex tagging method and a…

Combined Tevatron upper limit ongg→H→W+W−and constraints on the Higgs boson mass in fourth-generation fermion models

2010

We combine results from searches by the CDF and D0 collaborations for a standard model Higgs boson (H) in the process gg -> H -> W+W- in p (p) over bar collisions at the Fermilab Tevatron Collider at root s = 1.96 TeV. With 4.8 fb(-1) of integrated luminosity analyzed at CDF and 5.4 fb(-1) at D0, the 95% confidence level upper limit on sigma(gg -> H) x B(H -> W+W-) is 1.75 pb at m(H) = 120 GeV, 0.38 pb at m(H) = 165 GeV, and 0.83 pb at m(H) = 200 GeV. Assuming the presence of a fourth sequential generation of fermions with large masses, we exclude at the 95% confidence level a standard-model-like Higgs boson with a mass between 131 and 204 GeV.

Measurement of the Higgs boson mass from theH→γγandH→ZZ*→4ℓchannels inppcollisions at center-of-mass energies of 7 and 8 TeV with the ATLAS detector

2014

An improved measurement of the mass of the Higgs boson is derived from a combined fit to the reconstructed invariant mass spectra of the decay channels H -> gamma gamma and H -> ZZ* -> 4l. The analysis uses the pp collision data sample recorded by the ATLAS experiment at the CERN Large Hadron Collider at center-of-mass energies of 7 TeV and 8 TeV, corresponding to an integrated luminosity of 25 fb(-1). The measured value of the Higgs boson mass is m(H) = 125.36 +/- 0.37(stat) +/- 0.18 (syst) GeV. This result is based on improved energy-scale calibrations for photons, electrons, and muons as well as other analysis improvements, and supersedes the previous result from ATLAS. Upper limits on t…

Search for Pair Production of Supersymmetric Top Quarks in Dilepton Events frompp¯Collisions ats=1.96  TeV

2010

We present the results of a search for pair production of the supersymmetric partner of the top quark (the top squark (t) over tilde (1)) decaying to a b quark and a chargino (chi) over tilde (+/-)(1) with a subsequent (chi) over tilde (+/-)(1) decay into a neutralino (chi) over tilde (0)(1), lepton l, and neutrino nu Using a data sample corresponding to 2.7 fb(-1) of integrated luminosity of p (p) over bar collisions at root s = 1: 96 TeV collected by the CDF II detector, we reconstruct the mass of top squark candidate events and fit the observed mass spectrum to a combination of standard model processes and (t) over tilde (1)(t) over tilde (1). We find no evidence for (t) over tilde (1)(t…

Search for squarks and gluinos in final states with jets and missing transverse momentum using 36  fb−1 of s=13  TeV pp collision data with the ATLAS…

2018

A search for the supersymmetric partners of quarks and gluons (squarks and gluinos) in final states containing hadronic jets and missing transverse momentum, but no electrons or muons, is presented ...

Direct Measurement of theWProduction Charge Asymmetry inpp¯Collisions ats=1.96  TeV

2009

We wish to thank R.S. Thorne and W.J. Stirling for useful discussions on the theoretical predictions.We thank the Fermilab staff and the technical staffs of the participating institutions for their vital contributions. This work was supported by the U.S. Department of Energy and National Science Foundation; the Italian Istituto Nazionale di Fisica Nucleare; the Ministry of Education, Culture, Sports, Science and Technology of Japan; the Natural Sciences and Engineering Research Council of Canada; the National Science Council of the Republic of China; the Swiss National Science Foundation; the A.P. Sloan Foundation; the Bundesministerium fur Bildung und Forschung, Germany; the Korean Science…

Measurement of the top pair production cross section in 8 TeV proton-proton collisions using kinematic information in thelepton+jetsfinal state with …

2015

A measurement is presented of the (tt) over bar inclusive production cross section in pp collisions at a center-ofmass energy of pffisffiffi root s = 8 TeV using data collected by the ATLAS detector at the CERN Large Hadron Collider. The measurement was performed in the lepton + jets final state using a data set corresponding to an integrated luminosity of 20.3 fb(-1). The cross section was obtained using a likelihood discriminant fit and b-jet identification was used to improve the signal-to-background ratio. The inclusive (tt) over bar production cross section was measured to be 260 +/- 1(stat)(-23)(+22)(stat) +/- 8(lumi) +/- 4(beam) pb assuming a top-quark mass of 172.5 GeV, in good agre…

Measurement of the charge asymmetry in top quark pair production in pp collisions at root s=7 TeV using the ATLAS detector

2012

A measurement of the top-antitop production charge asymmetry A[subscript C] is presented using data corresponding to an integrated luminosity of 1.04 fb[superscript −1] of pp collisions at s√=7 TeV collected by the ATLAS detector at the LHC. Events are selected with a single lepton (electron or muon), missing transverse momentum and at least four jets of which at least one jet is identified as coming from a b-quark. A kinematic fit is used to reconstruct the t[bar over t] event topology. After background subtraction, a Bayesian unfolding procedure is performed to correct for acceptance and detector effects. The measured value of A[subscript C] is A[subscript C]=−0.019±0.028 (stat.)±0.024 (s…

Search for Technicolor Particles Produced in Association with a W Boson at CDF

2010

7 páginas, 3 figuras, 1 tabla.-- PACS numbers: 14.80.Tt, 12.60.Nz, 13.85.Rm.-- CDF Collaboration: et al.

Measurement of the flavour composition of dijet events in pp collisions at √s = 7 TeV with the ATLAS detector

2013

This paper describes a measurement of the flavour composition of dijet events produced in pp collisions at s√=7~TeVs=7~TeV using the ATLAS detector. The measurement uses the full 2010 data sample, corresponding to an integrated luminosity of 39 pb−1. Six possible combinations of light, charm and bottom jets are identified in the dijet events, where the jet flavour is defined by the presence of bottom, charm or solely light flavour hadrons in the jet. Kinematic variables, based on the properties of displaced decay vertices and optimised for jet flavour identification, are used in a multidimensional template fit to measure the fractions of these dijet flavour states as functions of the leadin…

Updated Search for the Flavor-Changing Neutral-Current Decay D^0 \to {\mu} + {\mu}-

2010

We report on a search for the flavor-changing neutral-current decay D0 \to {\mu}+ {\mu}- in pp collisions at \surd s = 1.96 TeV using 360 pb-1 of integrated luminosity collected by the CDF II detector at the Fermilab Tevatron collider. A displaced vertex trigger selects long-lived D0 candidates in the {\mu}+ {\mu}-, {\pi}+{\pi}-, and K-{\pi}+ decay modes. We use the Cabibbo-favored D0 \to K-{\pi}+ channel to optimize the selection criteria in an unbiased manner, and the kinematically similar D0 \to{\pi}+ {\pi}- channel for normalization. We set an upper limit on the branching fraction (D0 --> {\mu}+ {\mu}-) < 2.1 E-7 (3.0 E-7) at the 90% (95%) confidence level.

Search for Charged Higgs Bosons in Decays of Top Quarks inpp¯Collisions ats=1.96  TeV

2009

We report on the first direct search for charged Higgs bosons in decays of top quarks in p{bar p} collisions at {radical}s = 1.96 TeV. The search uses a data sample corresponding to an integrated luminosity of 2.2 fb{sup -1} collected by the CDF II detector at Fermilab, and looks for a resonance in the invariant mass distribution of two jets in the lepton+jets sample of t{bar t} candidates. We observe no evidence of charged Higgs bosons in top quark decays. Hence, 95% upper limits on the top quark decay branching ratio are placed at {Beta}(t {yields} H{sup +}b) < 0.1 to 0.3 for charged Higgs boson masses of 60 to 150 GeV/c{sup 2}, assuming {Beta}(H{sup +} {yields} c{bar s}) = 1.0. The upper…

Direct Bound on the Total Decay Width of the Top Quark inpp¯Collisions ats=1.96  TeV

2009

We present the first direct experimental bound on the total decay width of the top quark, Gamma(t), using 955 pb(-1) of the Tevatron's p (p) over bar collisions recorded by the Collider Detector at Fermilab. We identify 253 top-antitop pair candidate events. The distribution of reconstructed top quark mass from these events is fitted to templates representing different values of the top quark width. Using a confidence interval based on likelihood-ratio ordering, we extract an upper limit at 95% C.L. of Gamma(t) < 13.1 GeV for an assumed top quark mass of 175 GeV/c(2).

Measurement of the azimuthal anisotropy for charged particle production insNN=2.76TeV lead-lead collisions with the ATLAS detector

2012

Differential measurements of charged particle azimuthal anisotropy are presented for lead-lead collisions at root sNN = 2.76 TeV with the ATLAS detector at the LHC, based on an integrated luminosity of approximately 8 mu b(-1). This anisotropy is characterized via a Fourier expansion of the distribution of charged particles in azimuthal angle relative to the reaction plane, with the coefficients v(n) denoting the magnitude of the anisotropy. Significant v(2)-v(6) values are obtained as a function of transverse momentum (0.5 = 3 are found to vary weakly with both eta and centrality, and their p(T) dependencies are found to follow an approximate scaling relation, v(n)(1/n)(p(T)) proportional …

Measurement of the top quark pair production cross-section with ATLAS in the single lepton channel

2012

A measurement of the production cross-section for top quark pairs (t[bar over t]) in pp collisions at √s = 7 TeV is presented using data recorded with the ATLAS detector at the Large Hadron Collider. Events are selected in the single lepton topology by requiring an electron or muon, large missing transverse momentum and at least three jets. With a data sample of 35 pb[superscript −1], two different multivariate methods, one of which uses b-quark jet identification while the other does not, use kinematic variables to obtain cross-section measurements of σ[subscript t bar over t] = 187 ± 11 (stat.) [+18 over −17] (syst.) ± 6 (lumi.) pb and σ[subscript t bar over t] = 173 ± 17 (stat.) [+18 ove…

Search for an Invisibly Decaying Z′ Boson at Belle II in e+e−→μ+μ−(e±μ∓) Plus Missing Energy Final States

2020

Theories beyond the standard model often predict the existence of an additional neutral boson, the Z′. Using data collected by the Belle II experiment during 2018 at the SuperKEKB collider, we perform the first searches for the invisible decay of a Z′ in the process e+e-→μ+μ-Z′ and of a lepton-flavor-violating Z′ in e+e-→e±μZ′. We do not find any excess of events and set 90% credibility level upper limits on the cross sections of these processes. We translate the former, in the framework of an Lμ-Lτ theory, into upper limits on the Z′ coupling constant at the level of 5×10-2-1 for MZ′≤6 GeV/c2.

A search for flavour changing neutral currents in top-quark decays in pp collision data collected with the ATLAS detector at root s=7 TeV

2012

A search for flavour changing neutral current (FCNC) processes in top-quark decays by the ATLAS Collaboration is presented. Data collected from pp collisions at the LHC at a centre-of-mass energy of √s = 7 TeV during 2011, corresponding to an integrated luminosity of 2.1 fb[superscript −1], were used. A search was performed for top-quark pair-production events, with one top quark decaying through the t → Zq FCNC (q = u, c) channel, and the other through the Standard Model dominant mode t → W b. Only the decays of the Z boson to charged leptons and leptonic W -boson decays were considered as signal. Consequently, the final-state topology is characterised by the presence of three isolated cha…

Evidence ofWγγProduction inppCollisions ats=8  TeVand Limits on Anomalous Quartic Gauge Couplings with the ATLAS Detector

2015

This Letter reports evidence of triple gauge boson production pp -> W(l nu)gamma gamma + X, which is accessible for the first time with the 8 TeV LHC data set. The fiducial cross section for this process is measured in a data sample corresponding to an integrated luminosity of 20.3 fb(-1), collected by the ATLAS detector in 2012. Events are selected using the W boson decay to e nu or mu nu as well as requiring two isolated photons. The measured cross section is used to set limits on anomalous quartic gauge couplings in the high diphoton mass region.

Search for High-Masse+e−Resonances inpp¯Collisions ats=1.96  TeV

2009

We thank the Fermilab staff and the technical staffs of the participating institutions for their vital contributions. This work was supported by the U.S. Department of Energy and National Science Foundation; the Italian Istituto Nazionale di Fisica Nucleare; the Ministry of Education, Culture, Sports, Science and Technology of Japan; the Natural Sciences and Engineering Research Council of Canada; the National Science Council of the Republic of China; the Swiss National Science Foundation; the A.P. Sloan Foundation; the Bundesministerium fur Bildung und Forschung, Germany; the Korean Science and Engineering Foundation and the Korean Research Foundation; the Science and Technology Facilities…

Search for a fermiophobic Higgs boson in the diphoton decay channel with the ATLAS detector

2012

[Excerpt] A search for a fermiophobic Higgs boson using diphoton events produced in proton-proton collisions at a centre-of-mass energy of s√=7 TeV is performed using data corresponding to an integrated luminosity of 4.9 fb−1 collected by the ATLAS experiment at the Large Hadron Collider. A specific benchmark model is considered where all the fermion couplings to the Higgs boson are set to zero and the bosonic couplings are kept at the Standard Model values (fermiophobic Higgs model). The largest excess with respect to the background-only hypothesis is found at 125.5 GeV, with a local significance of 2.9 standard deviations, which reduces to 1.6 standard deviations when taking into account …

Probing the Quantum Interference between Singly and Doubly Resonant Top-Quark Production in pp Collisions at s=13  TeV with the ATLAS Detector

2018

This Letter presents a normalized differential cross-section measurement in a fiducial phase-space region where interference effects between top-quark pair production and associated production of a single top quark with a W boson and a b-quark are significant. Events with exactly two leptons (ee, μμ, or eμ) and two b-tagged jets that satisfy a multiparticle invariant mass requirement are selected from 36.1  fb^{-1} of proton-proton collision data taken at sqrt[s]=13  TeV with the ATLAS detector at the LHC in 2015 and 2016. The results are compared with predictions from simulations using various strategies for the interference. The standard prescriptions for interference modeling are signifi…

Measurement of theW+W−Cross Section ins=7  TeVppCollisions with ATLAS

2011

This Letter presents a measurement of the W+W- production cross section in root s = 7 TeV pp collisions by the ATLAS experiment, using 34 pb(-1) of integrated luminosity produced by the Large Hadron Collider at CERN. Selecting events with two isolated leptons, each either an electron or a muon, 8 candidate events are observed with an expected background of 1.7 +/- 0.6 events. The measured cross section is 41(-16)(+20)(stat) +/- 5(syst) +/- 1(lumi) pb, which is consistent with the standard model prediction of 44 +/- 3 pb calculated at next-to-leading order in QCD.

Measurement of the cross section of high transverse momentumZ→bb¯production in proton–proton collisions ats=8 TeVwith the ATLAS detector

2014

This Letter reports the observation of a high transverse momentum Z -> b (b) over bar signal in proton-proton collisions at root s = 8TeVand the measurement of its production cross section. The data analysed were collected in 2012 with the ATLAS detector at the LHC and correspond to an integrated luminosity of 19.5 fb(-1). The Z -> b (b) over bar decay is reconstructed from a pair of b-tagged jets, clustered with the anti- k(t) jet algorithm with R = 0.4, that have low angular separation and form a dijet with p(T) > 200 GeV. The signal yield is extracted from a fit to the dijet invariant mass distribution, with the dominant, multi-jet background mass shape estimated by employing a fully dat…

Production ofψ(2S)mesons inpp¯collisions at 1.96 TeV

2009

We have measured the differential cross section for the inclusive production of $\ensuremath{\psi}(2\mathrm{S})$ mesons decaying to ${\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ that were produced in prompt or $B$-decay processes from $p\overline{p}$ collisions at 1.96 TeV. These measurements have been made using a data set from an integrated luminosity of $1.1\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ collected by the CDF II detector at Fermilab. For events with transverse momentum ${p}_{T}(\ensuremath{\psi}(2\mathrm{S}))g2\text{ }\text{ }\mathrm{GeV}/c$ and rapidity $|y(\ensuremath{\psi}(2\mathrm{S}))|l0.6$ we measure the integrated inclusive cross section $\ensuremath…

Study of the associated production of photons andb-quark jets inpp¯collisions ats=1.96  TeV

2010

The cross section for photon production in association with at least one jet containing a b quark has been measured in proton antiproton collisions at {radical}(s)=1.96 TeV. The data sample used corresponds to an integrated luminosity of 340 pb{sup -1} collected with the CDF II detector. Both the differential cross section as a function of photon transverse energy E{sub T}{sup {gamma}}and the total cross section are measured and compared to a next-to-leading order prediction for the process.

The ATLAS Data Acquisition and High Level Trigger system

2016

Journal of Instrumentation 11(06), P06008 (2016). doi:10.1088/1748-0221/11/06/P06008

Search for single top quark production inpp¯collisions ats=1.96  TeVin the missing transverse energy plus jets topology

2010

We report a search for single top quark production with the CDF II detector using 2.1 fb{sup -1} of integrated luminosity of pp collisions at {radical}(s)=1.96 TeV. The data selected consist of events characterized by large energy imbalance in the transverse plane and hadronic jets, and no identified electrons and muons, so the sample is enriched in W{yields}{tau}{nu} decays. In order to suppress backgrounds, additional kinematic and topological requirements are imposed through a neural network, and at least one of the jets must be identified as a b quark jet. We measure an excess of signal-like events in agreement with the standard model prediction, but inconsistent with a model without si…

Search for top squarks decaying to tau sleptons in pp collisions at s=13  TeV with the ATLAS detector

2018

A search for direct pair production of top squarks in final states with two tau leptons, b-jets, and missing transverse momentum is presented. The analysis is based on proton-proton collision data ...

Measurement of theb-hadron production cross section using decays toμ−D0Xfinal states inpp¯collisions ats=1.96  TeV

2009

We report a measurement of the production cross section for b hadrons in p{bar p} collisions at {radical}s = 1.96 TeV. Using a data sample derived from an integrated luminosity 83 pb{sup -1} collected with the upgraded Collider Detector (CDF II) at the Fermilab Tevatron, we analyze b hadrons, H{sub b}, partially reconstructed in the semileptonic decay mode H{sub b} {yields} {mu}{sup -} D{sup 0} X. Our measurement of the inclusive production cross section for b hadrons with transverse momentum p{sub T} > 9 GeV/c and rapidity |y| < 0.6 is {sigma} = 1.30 {micro}b {+-} 0.05 {micro}b(stat) {+-} 0.14 {micro}b(syst) {+-} 0.07 {micro}b({Beta}), where the uncertainties are statistical, systematic, a…

Search forR-Parity Violating Decays of Sneutrinos toeμ,μτ, andeτPairs inpp¯Collisions ats=1.96  TeV

2010

7 paginas, 2 figuras, 3 tablas.-- PACS numbers: 14.80.Ly, 12.60.Jv, 13.85.Qk, 14.60.St.--CDF Collaboration: et al.

Search for dark matter in association with a Higgs boson decaying to two photons at s=13  TeV with the ATLAS detector

2017

A search for dark matter in association with a Higgs boson decaying to two photons is presented. This study is based on data collected with the ATLAS detector, corresponding to an integrated lumino ...

The ATLAS Simulation Infrastructure

2010

52 páginas, 10 figuras, 18 tablas.-- This article is distributed under the terms of the Creative Commons Attribution Noncommercial License.-- et al. (The ATLAS Collaboration).

Jet mass and substructure of inclusive jets in $ \sqrt {s} = 7\;{\text{TeV}} $ pp collisions with the ATLAS experiment

2012

Recent studies have highlighted the potential of jet substructure techniques to identify the hadronic decays of boosted heavy particles. These studies all rely upon the assumption that the internal substructure of jets generated by QCD radiation is well understood. In this article, this assumption is tested on an inclusive sample of jets recorded with the ATLAS detector in 2010, which corresponds to 35 pb-1 of pp collisions delivered by the LHC at √s = 7TeV. In a subsample of events with single pp collisions, measurements corrected for detector efficiency and resolution are presented with full systematic uncertainties. Jet invariant mass, kt splitting scales and N-subjettiness variables are…

Measurement of the fraction oftt¯production via gluon-gluon fusion inpp¯collisions ats=1.96  TeV

2009

We present a measurement of the ratio of the tt production cross section via gluon-gluon fusion to the total tt production cross section in pp collisions at √s=1.96  TeV at the Tevatron. Using a data sample with an integrated luminosity of 955  pb-1 recorded by the CDF II detector at Fermilab, we select events based on the tt decay to lepton+jets. Using an artificial neural network technique we discriminate between tt events produced via qq annihilation and gg fusion, and find Gf=σ(gg→tt )/σ(pp →tt )<0.33 at the 68% confidence level. This result is combined with a previous measurement to obtain the most stringent measurement of this quantity by CDF to date, Gf=0.07-0.07+0.15.

Measurements ofW±Zproduction cross sections inppcollisions ats=8  TeVwith the ATLAS detector and limits on anomalous gauge boson self-couplings

2016

This paper presents measurements of W(+/-)Z production in pp collisions at a center-of-mass energy of 8 TeV. The gauge bosons are reconstructed using their leptonic decay modes into electrons and m ...

Search for flavor-changing neutral currents in top quark decays t→Hc and t→Hu in multilepton final states in proton-proton collisions at s=13  TeV wi…

2018

Flavor-changing neutral currents are not present in the Standard Model at tree level and are suppressed in loop processes by the unitarity of the Cabibbo-Kobayashi-Maskawa matrix; the corresponding ...

Measurements of the pseudorapidity dependence of the total transverse energy in proton-proton collisions at sqrt(s) = 7 TeV with ATLAS

2012

This paper describes measurements of the sum of the transverse energy of particles as a function of particle pseudorapidity, η, in proton-proton collisions at a centre-of-mass energy, √s = 7 TeV using the ATLAS detector at the Large Hadron Collider. The measurements are performed in the region |η| < 4.8 for two event classes: those requiring the presence of particles with a low transverse momentum and those requiring particles with a significant transverse momentum. In the second dataset measurements are made in the region transverse to the hard scatter. The distributions are compared to the predictions of various Monte Carlo event generators, which generally tend to underestimate the amoun…

Search for Supersymmetry inpp¯Collisions ats=1.96  TeVUsing the Trilepton Signature for Chargino-Neutralino Production

2008

We use the three lepton and missing energy trilepton signature to search for chargino-neutralino production with 2.0 fb(-1) of integrated luminosity collected by the CDF II experiment at the Tevatron p (p) over bar collider. We expect an excess of approximately 11 supersymmetric events for a choice of parameters of the mSUGRA model, but our observation of 7 events is consistent with the standard model expectation of 6.4 events. We constrain the mSUGRA model of supersymmetry and rule out chargino masses up to 145 GeV/c(2) for a specific choice of parameters.

Search for new phenomena in events with a photon and missing transverse momentum inppcollisions ats=8  TeVwith the ATLAS detector

2015

© 2015 CERN. © 2015 CERN, for the ATLAS Collaboration. Published by the American Physical Society under the terms of the »http://creativecommons.org/licenses/by/3.0/» Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Results of a search for new phenomena in events with an energetic photon and large missing transverse momentum with the ATLAS experiment at the LHC are reported. Data were collected in proton-proton collisions at a center-of-mass energy of 8 TeV and correspond to an integrated luminosity of 20.3 fb-1. The observed data are well described by the expe…

Search for the Associated Production of the Standard-Model Higgs Boson in the All-Hadronic Channel

2009

We report on a search for the standard-model Higgs boson in pp collisions at s=1.96 TeV using an integrated luminosity of 2.0 fb(-1). We look for production of the Higgs boson decaying to a pair of bottom quarks in association with a vector boson V (W or Z) decaying to quarks, resulting in a four-jet final state. Two of the jets are required to have secondary vertices consistent with B-hadron decays. We set the first 95% confidence level upper limit on the VH production cross section with V(-> qq/qq('))H(-> bb) decay for Higgs boson masses of 100-150 GeV/c(2) using data from run II at the Fermilab Tevatron. For m(H)=120 GeV/c(2), we exclude cross sections larger than 38 times the standard-m…

Search for Axionlike Particles Produced in e+e− Collisions at Belle II

2020

We present a search for the direct production of a light pseudoscalar a decaying into two photons with the Belle II detector at the SuperKEKB collider. We search for the process e+e-→γa, a→γγ in the mass range 0.2<ma<9.7 GeV/c2 using data corresponding to an integrated luminosity of (445±3) pb-1. Light pseudoscalars interacting predominantly with standard model gauge bosons (so-called axionlike particles or ALPs) are frequently postulated in extensions of the standard model. We find no evidence for ALPs and set 95% confidence level upper limits on the coupling strength gaγγ of ALPs to photons at the level of 10-3 GeV-1. The limits are the most restrictive to date for 0.2<ma<1 GeV/c2.

Production of Muons from Heavy Flavor Decays at Forward Rapidity inppand Pb-Pb Collisions atsNN=2.76  TeV

2012

The ALICE Collaboration has measured the inclusive production of muons from heavy-flavor decays at forward rapidity, 2.5 < y < 4, in pp and Pb-Pb collisions at root s(NN) = 2.76 TeV. The p(t)-differential inclusive cross section of muons from heavy-flavor decays in pp collisions is compared to perturbative QCD calculations. The nuclear modification factor is studied as a function of p(t) and collision centrality. A weak suppression is measured in peripheral collisions. In the most central collisions, a suppression of a factor of about 3-4 is observed in 6 < p(t) < 10 GeV/c. The suppression shows no significant p(t) dependence.

Search for a Standard Model Higgs Boson in theH→ZZ→ℓ+ℓ−νν¯Decay Channel with the ATLAS Detector

2011

A search for a heavy standard model Higgs boson decaying via H -> ZZ -> l(+)l(-)v (v) over bar, where l = e, mu, is presented. It is based on proton-proton collision data at root s = 7 TeV, collected by the ATLAS experiment at the LHC in the first half of 2011 and corresponding to an integrated luminosity of 1.04 fb(-1). The data are compared to the expected standard model backgrounds. The data and the background expectations are found to be in agreement and upper limits are placed on the Higgs boson production cross section over the entire mass window considered; in particular, the production of a standard model Higgs boson is excluded in the region 340 < m(H) < 450 GeV at the 95% confiden…

A study of the material in the ATLAS inner detector using secondary hadronic interactions

2011

The ATLAS inner detector is used to reconstruct secondary vertices due to hadronic interactions of primary collision products, so probing the location and amount of material in the inner region of ATLAS. Data collected in 7 TeV pp collisions at the LHC, with a minimum bias trigger, are used for comparisons with simulated events. The reconstructed secondary vertices have spatial resolutions ranging from ~ 200μm to 1 mm. The overall material description in the simulation is validated to within an experimental uncertainty of about 7%. This will lead to a better understanding of the reconstruction of various objects such as tracks, leptons, jets, and missing transverse momentum.

EXTRACTION OF ΛΛ SCATTERING LENGTH

2009

We determine ΛΛ scattering parameters from a ΛΛ invariant mass spectrum that was obtained by 12 C (K-, K+ΛΛ) reaction at the KEK Proton Synchrotron. In the framework of Watson's procedure, the obtained scattering length [Formula: see text] and effective range [Formula: see text] are most consistent with the values predicted by using the Nijmegen soft core models (NSC97's). However, the predicted values by using the Nijmegen hard-core ND ( G -matrix) and the extended soft-core (ESC00) models are out of two standard deviations from the determined scattering parameters.

Observation of Coulomb-assisted nuclear bound state of $��^-$-$^{14}$N system

2020

In an emulsion-counter hybrid experiment performed at J-PARC, a $��^-$ absorption event was observed which decayed into twin single-$��$ hypernuclei. Kinematic calculations enabled a unique identification of the reaction process as $��^{-} + ^{14}$N$\ \rightarrow\ ^{10}_��$Be + $^5_��$He. For the binding energy of the $��^{-}$ hyperon in the $��^-$-$^{14}$N system a value of $1.27 \pm 0.21$ MeV was deduced. The energy level of $��^-$ is likely a nuclear $1p$ state which indicates a weak $��N$-$����$ coupling.

Measurement of the cross section for top-quark pair production in pp collisions at √s = 7TeV with the ATLAS detector using final states with two high…

2012

A measurement is reported of the production cross section of top-quark pairs (tt¯) in proton-proton collisions at a center-of-mass energy of 7 TeV recorded with the ATLAS detector at the LHC. Candidate events have a signature consistent with containing two isolated leptons, large missing transverse momentum, and at least two jets. Using a data sample corresponding to an integrated luminosity of 0.70 fb−1, a tt¯ production cross section σtt¯=176±5(stat.)+14−11(syst.)±8(lum.) pb is measured for an assumed top-quark mass of mt = 172.5 GeV. This measurement is in good agreement with Standard Model predictions.

Evidence for the associated production of a W boson and a top quark in ATLAS at √s = 7 TeV

2012

This Letter presents evidence for the associated production of a W boson and a top quark using 2.05 fb[superscript −1] of pp collision data at √s = 7 TeV accumulated with the ATLAS detector at the LHC. The analysis is based on the selection of the dileptonic final states with events featuring two isolated leptons, electron or muon, with significant transverse missing momentum and at least one jet. An approach based on boosted decision trees has been developed to improve the discrimination of single top-quark Wt events from background. A template fit to the final classifier distributions is performed to determine the cross-section. The result is incompatible with the background-only hypothes…

Measurements of Higgs boson production and couplings in diboson final states with the ATLAS detector at the LHC

2013

We acknowledge the support of ANPCyT, Argentina; YerPhI, Armenia; ARC, Australia; BMWF and FWF, Austria; ANAS, Azerbaijan; SSTC, Belarus; CNPq and FAPESP, Brazil; NSERC, NRC and CFI, Canada; CERN; CONICYT, Chile; CAS, MOST and NSFC, China; COLCIENCIAS, Colombia; MSMT CR, MPO CR and VSC CR, Czech Republic; DNRF, DNSRC and Lundbeck Foundation, Denmark; EPLANET, ERC and NSRF, European Union; IN2P3-CNRS, CEA-DSM/IRFU, France; GNSF, Georgia; BMBF, DFG, HGF, MPG and AvH Foundation, Germany; GSRT and NSRF, Greece; ISF, MINERVA, GIF, DIP and Benoziyo Center, Israel; INFN, Italy; MEXT and JSPS, Japan; CNRST, Morocco; FOM and NWO, Netherlands; BRF and RCN, Norway; MNiSW, Poland; GRICES and FCT, Portu…

Present status and first results of the final focus beam line at the KEK Accelerator Test Facility

2011

ATF2 is a final-focus test beam line which aims to focus the low emittance beam from the ATF damping ring to a vertical size of about 37 nm and to demonstrate nanometer level beam stability. Several advanced beam diagnostics and feedback tools are used. In December 2008, construction and installation were completed and beam commissioning started, supported by an international team of Asian, European, and U.S. scientists. The present status and first results are described.

Search for a multi-Higgs-boson cascade inW+W−bb¯events with the ATLAS detector inppcollisions ats=8  TeV

2014

A search is presented for new particles in an extension to the Standard Model that includes a heavy Higgs boson (H-0), an intermediate charged Higgs-boson pair (H-+/-), and a light Higgs boson (h(0)). The analysis searches for events involving the production of a single heavy neutral Higgs boson which decays to the charged Higgs boson and a W boson, where the charged Higgs boson subsequently decays into a W boson and the lightest neutral Higgs boson decaying to a bottom-antibottom-quark pair. Such a cascade results in a W-boson pair and a bottom-antibottom-quark pair in the final state. Events with exactly one lepton, missing transverse momentum, and at least four jets are selected from a d…

Search for high-mass states with one lepton plus missing transverse momentum in proton–proton collisions at s=7 TeV with the ATLAS detector

2011

The ATLAS detector is used to search for high-mass states, such as heavy charged gauge bosons (W', W*) decaying to a charged lepton (electron or muon) and a neutrino. Results are presented based on the analysis of pp collisions at a center-of-mass energy of 7 TeV corresponding to an integrated luminosity of 36 pb-1. No excess beyond standard model expectations is observed. A W' with sequential standard model couplings is excluded at 95% confidence level for masses below 1.49 TeV, and a W*(charged chiral boson) for masses below 1.47 TeV.

Search for a Heavy Toplike Quark inpp¯Collisions ats=1.96  TeV

2011

We present the results of a search for pair production of a heavy toplike (t') quark decaying to Wq final states using data corresponding to an integrated luminosity of 5.6 fb(-1) collected by the CDF II detector in pp collisions at √s=1.96 TeV. We perform parallel searches for t'→Wb and t'→Wq (where q is a generic down-type quark) in events containing a lepton and four or more jets. By performing a fit to the two-dimensional distribution of total transverse energy versus reconstructed t' quark mass, we set upper limits on the t't' production cross section and exclude a standard model fourth-generation t' quark decaying to Wb (Wq) with mass below 358 (340) GeV/c(2) at 95% C.L.

Measurement of theWW+WZProduction Cross Section Using thelepton+jetsFinal State at CDF II

2010

We report two complementary measurements of the diboson (WW + WZ) cross section in the final state consisting of an electron or muon, missing transverse energy, and jets, performed using p{bar p} collision data at {radical}s = 1.96 TeV collected by the Collider Detector at Fermilab. The first method uses the dijet invariant mass distribution while the second method uses more of the kinematic information in the event through matrix-element calculations of the signal and background processes and has a higher sensitivity. The result from the second method has a signal significance of 5.4{sigma} and is the first observation of WW + WZ production using this signature. Combining the results from …

Searches for Higgs boson pair production in thehh→bbττ,γγWW*,γγbb,bbbbchannels with the ATLAS detector

2015

Searches for both resonant and nonresonant Higgs boson pair production are performed in the hh -> bb tau tau, gamma gamma WW* final states using 20.3 fb(-1) of pp collision data at a center-of-m ...

Measurement of the top quark mass using the invariant mass of lepton pairs in soft muon b-tagged events

2009

We present the first measurement of the mass of the top quark in a sample of t (t) over bar -> l (nu) over barb (b) over barq (q) over bar events (where l = e, mu) selected by identifying jets containing a muon candidate from the semileptonic decay of heavy-flavor hadrons (soft muon b tagging). The p (p) over bar collision data used correspond to an integrated luminosity of 2 fb(-1) and were collected by the CDF II detector at the Fermilab Tevatron Collider. The measurement is based on a novel technique exploiting the invariant mass of a subset of the decay particles, specifically the lepton from the W boson of the t -> Wb decay and the muon from a semileptonic b decay. We fit template hist…

Measurement of Inclusive Jet Cross Sections inZ/γ*(→e+e−)+jetsProduction inpp¯Collisions ats=1.96   TeV

2008

Inclusive jet cross sections in Z/{gamma}* events, with Z/{gamma}* decaying into an electron-positron pair, are measured as a function of jet transverse momentum and jet multiplicity in p{bar p} collisions at {radical}s - 1.96 TeV with the upgraded Collider Detector at Fermilab in Run II, based on an integrated luminosity of 1.7 fb{sup -1}. The measurements cover the rapidity region |y{sup jet}| 30 GeV/c. Next-to-leading order perturbative QCD predictions are in good agreement with the measured cross sections.

Precision Measurement of theX(3872)Mass inJ/ψπ+π−Decays

2009

We present an analysis of the mass of the X(3872) reconstructed via its decay to J/psi pi(+)pi(-) using 2.4 fb(-1) of integrated luminosity from p (p) over bar collisions at root s = 1.96 TeV, collected with the CDF II detector at the Fermilab Tevatron. The possible existence of two nearby mass states is investigated. Within the limits of our experimental resolution the data are consistent with a single state, and having no evidence for two states we set upper limits on the mass difference between two hypothetical states for different assumed ratios of contributions to the observed peak. For equal contributions, the 95% confidence level upper limit on the mass difference is 3.6 MeV/c(2). Un…

Measurement of the transverse polarization ofΛandΛ¯hyperons produced in proton-proton collisions ats=7  TeVusing the ATLAS detector

2015

The transverse polarization of Λ and Λ¯ hyperons produced in proton-proton collisions at a center-of-mass energy of 7 TeV is measured. The analysis uses 760  μb−1 of minimum bias data collected by the ATLAS detector at the LHC in the year 2010. The measured transverse polarization averaged over Feynman xF from 5×10−5 to 0.01 and transverse momentum pT from 0.8 to 15 GeV is −0.010±0.005(stat)±0.004(syst) for Λ and 0.002±0.006(stat)±0.004(syst) for Λ¯. It is also measured as a function of xF and pT, but no significant dependence on these variables is observed. Prior to this measurement, the polarization was measured at fixed-target experiments with center-of-mass energies up to about 40 GeV. …

Measurements of the top-quark mass using charged particle tracking

2010

21 páginas, 13 figuras, 6 tablas.-- PACS numbers: 12.15.-y, 13.85.-t, 14.60.-z, 14.65.Fy.-- CDF Collaboration: et al.

Search for resonant top quark plus jet production intt¯+jetsevents with the ATLAS detector inppcollisions ats=7  TeV

2012

This paper presents a search for a new heavy particle produced in association with a top or antitop quark. Two models in which the new heavy particle is a color singlet or a color triplet are considered, decaying, respectively, to (t)over-barq or tq, leading to a resonance within the t(t)over-bar + jets signature. The full 2011 ATLAS pp collision data set from the LHC (4.7 fb(-1)) is used to search for t(t)over-bar events produced in association with jets, in which one of the W bosons from the top quarks decays leptonically and the other decays hadronically. The data are consistent with the Standard Model expectation, and a new particle with mass below 430 Gev for both W' boson and color tr…

Characterisation and mitigation of beam-induced backgrounds observed in the ATLAS detector during the 2011 proton-proton run

2013

This paper presents a summary of beam-induced backgrounds observed in the ATLAS detector and discusses methods to tag and remove background contaminated events in data. Triggerrate based monitoring of beam-related backgrounds is presented. The correlations of backgrounds with machine conditions, such as residual pressure in the beam-pipe, are discussed. Results from dedicated beam-background simulations are shown, and their qualitative agreement with data is evaluated. Data taken during the passage of unpaired, i.e. non-colliding, proton bunches is used to obtain background-enriched data samples. These are used to identify characteristic features of beam-induced backgrounds, which then are …

Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS

2012

We present the results of a search for new, heavy particles that decay at a significant distance from their production point into a final state containing charged hadrons in association with a high-momentum muon. The search is conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV and an integrated luminosity of 33 pb[superscript −1] collected in 2010 by the ATLAS detector operating at the Large Hadron Collider. Production of such particles is expected in various scenarios of physics beyond the standard model. We observe no signal and place limits on the production cross-section of supersymmetric particles in an R-parity-violating scenario as a function of the neutral…

Search for Scalar Charm Quark Pair Production inppCollisions ats=8  TeVwith the ATLAS Detector

2015

The results of a dedicated search for pair production of scalar partners of charm quarks are reported. The search is based on an integrated luminosity of 20.3 fb(-1) of pp collisions at root s = 8 TeV recorded with the ATLAS detector at the LHC. The search is performed using events with large missing transverse momentum and at least two jets, where the two leading jets are each tagged as originating from c quarks. Events containing isolated electrons or muons are vetoed. In an R-parity-conserving minimal super-symmetric scenario in which a single scalar-charm state is kinematically accessible, and where it decays exclusively into a charm quark and a neutralino, 95% confidence-level upper li…

Measurement of the azimuthal ordering of charged hadrons with the ATLAS detector

2012

This paper presents a study of the possible ordering of charged hadrons in the azimuthal angle relative to the beam axis in high-energy proton-proton collisions at the Large Hadron Collider (LHC). A spectral analysis of correlations between longitudinal and transverse components of the momentum of the charged hadrons, driven by the search for phenomena related to the structure of the QCD field, is performed. Data were recorded with the ATLAS detector at center-of-mass energies of √s=900  GeV and √s=7  TeV. The correlations measured in a kinematic region dominated by low-pT particles are not well described by conventional models of hadron production. The measured spectra show features consis…

First measurement of the ratio of branching fractionsB(Λb0→Λc+μ−ν¯μ)/B(Λb0→Λc+π−)

2009

This article presents the first measurement of the ratio of branching fractions B(Lambda(0)(b) -> Lambda(+)(c) mu(-) (nu) over bar (mu))/B(Lambda(0)(b) -> Lambda(+)(c) pi(-)). Measurements in two control samples using the same technique B((B) over bar (0) -> D+ mu(-) (nu) over bar (mu))/B((B) over bar (0) -> D+ pi(-)) and B((B) over bar (0) -> D*(2010)(+) mu(-) (nu) over bar (mu))/B((B) over bar (0) -> D*(2010)(+) pi(-)) are also reported. The analysis uses data from an integrated luminosity of approximately 172 pb(-1) of p (p) over bar collisions at root s = 1: 96 TeV, collected with the CDF II detector at the Fermilab Tevatron. The relative branching fractions are measured to be B(Lambda(…

Measurement of the Inelastic Proton-Proton Cross Section at s=13  TeV with the ATLAS Detector at the LHC

2016

This Letter presents a measurement of the inelastic proton-proton cross section using 60  μb^{-1} of pp collisions at a center-of-mass energy sqrt[s] of 13 TeV with the ATLAS detector at the LHC. Inelastic interactions are selected using rings of plastic scintillators in the forward region (2.07 10^{-6}, where M_{X} is the larger invariant mass of the two hadronic systems separated by the largest rapidity gap in the event. In this ξ range the scintillators are highly efficient. For diffractive events this corresponds to cases where at least one proton dissociates to a system with M_{X}>13  GeV. The measured cross section is compared with a range of theoretical predictions. When extrapolated…

Strong Evidence forZZProduction inpp¯Collisions ats=1.96  TeV

2008

We report the first measurement of the cross section for Z boson pair production at a hadron collider. This result is based on a data sample corresponding to 1.9 fb{sup -1} of integrated luminosity from p{bar p} collisions at {radical}s = 1.96 TeV collected with the CDF II detector at the Fermilab Tevatron. In the {ell}{ell}{ell}{prime}{ell}{prime} channel, we observe three ZZ candidates with an expected background of 0.096{sub -0.063}{sup +0.092} events. In the {ell}{ell}{nu}{nu} channel, we use a leading-order calculation of the relative ZZ and WW event probabilities to discriminate between signal and background. In the combination of {ell}{ell}{ell}{prime}{ell}{prime} and {ell}{ell}{nu}{…

Measurement of thepp¯→tt¯production cross section and the top quark mass ats=1.96  TeVin the all-hadronic decay mode

2007

We report the measurements of the t{bar t} production cross section and of the top quark mass using 1.02 fb{sup -1} of p{bar p} data collected with the CDF II detector at the Fermilab Tevatron. We select events with six or more jets on which a number of kinematical requirements are imposed by means of a neural network algorithm. At least one of these jets must be identified as initiated by a b-quark candidate by the reconstruction of a secondary vertex. The cross section is measured to be {sigma}{sub t{bar t}} = 8.3 {+-} 1.0(stat. ){sup +2.0}{sub -1.5}(syst.) {+-} 0.5(lumi.) pb, which is consistent with the standard model prediction. The top quark mass of 174.0 {+-} 2.2(stat.){+-}4.8(syst.)…

Measurement of the isolated diphoton cross section inppcollisions ats=7  TeVwith the ATLAS detector

2012

The ATLAS experiment has measured the production cross section of events with two isolated photons in the final state, in proton-proton collisions at √s=7  TeV. The full data set acquired in 2010 is used, corresponding to an integrated luminosity of 37  pb-1. The background, consisting of hadronic jets and isolated electrons, is estimated with fully data-driven techniques and subtracted. The differential cross sections, as functions of the di-photon mass (mγγ), total transverse momentum (pT,γγ), and azimuthal separation (Δϕγγ), are presented and compared to the predictions of next-to-leading-order QCD.

Search for new particles in two-jet final states in 7 TeV proton-proton collisions with the ATLAS detector at the LHC

2010

19 páginas, 2 figuras, 1 tabla.-- et al.(ATLAS Collaboration).

Search for a Fermiophobic Higgs Boson Decaying into Diphotons inpp¯Collisions ats=1.96  TeV

2009

A search for a narrow diphoton mass resonance is presented based on data from 3.0 fb{sup -1} of integrated luminosity from p{bar p} collisions at {radical}s = 1.96 TeV collected by the CDF experiment. No evidence of a resonance in the diphoton mass spectrum is observed, and upper limits are set on the cross section times branching fraction of the resonant state as a function of Higgs boson mass. The resulting limits exclude Higgs bosons with masses below 106 GeV/c{sup 2} at a 95% Bayesian credibility level (C.L.) for one fermiophobic benchmark model.

Measurement of inclusive two-particle angular correlations in pp collisions with the ATLAS detector at the LHC

2012

We present a measurement of two-particle angular correlations in proton- proton collisions at s√=900 GeV and 7 TeV. The collision events were collected during 2009 and 2010 with the ATLAS detector at the Large Hadron Collider using a single-arm minimum bias trigger. Correlations are measured for charged particles produced in the kinematic range of transverse momentum pT > 100 MeV and pseudorapidity |η| < 2.5. A complex structure in pseudorapidity and azimuth is observed at both collision energies. Results are compared to pythia 8 and herwig++ as well as to the AMBT2B, DW and Perugia 2011 tunes of pythia 6. The data are not satisfactorily described by any of these models.

Observation of s-Channel Production of Single Top Quarks at the Tevatron

2014

We report the first observation of single-top-quark production in the s channel through the combination of the CDF and D0 measurements of the cross section in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV. The data correspond to total integrated luminosities of up to 9.7fb-1 per experiment. The measured cross section is σs=1.29-0.24+0.26pb. The probability of observing a statistical fluctuation of the background to a cross section of the observed size or larger is 1.8×10-10, corresponding to a significance of 6.3 standard deviations for the presence of an s-channel contribution to the production of single-top quarks. © 2014 American Physical Society.

Determination of the Ratio ofb-Quark Fragmentation Fractionsfs/fdinppCollisions ats=7  TeVwith the ATLAS Detector

2015

With an integrated luminosity of 2.47 fb^{-1} recorded by the ATLAS experiment at the LHC, the exclusive decays B_{s}^{0}→J/ψϕ and B_{d}^{0}→J/ψK^{*0} of B mesons produced in pp collisions at sqrt[s]=7 TeV are used to determine the ratio of fragmentation fractions f_{s}/f_{d}. From the observed B_{s}^{0}→J/ψϕ and B_{d}^{0}→J/ψK^{*0} yields, the quantity (f_{s}/f_{d})[B(B_{s}^{0}→J/ψϕ)/B(B_{d}^{0}→J/ψK^{*0})] is measured to be 0.199±0.004(stat)±0.008(syst). Using a recent theory prediction for [B(B_{s}^{0}→J/ψϕ)/B(B_{d}^{0}→J/ψK^{*0})] yields (f_{s}/f_{d})=0.240±0.004(stat)±0.010(syst)±0.017(th). This result is based on a new approach that provides a significant improvement of the world aver…

Measurement of the Z→ττ cross section with the ATLAS detector

2011

Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UAM

First Evidence for cos2β&gt;0 and Resolution of the Cabibbo-Kobayashi-Maskawa Quark-Mixing Unitarity Triangle Ambiguity

2018

We present first evidence that the cosine of the CP-violating weak phase 2β is positive, and hence exclude trigonometric multifold solutions of the Cabibbo-Kobayashi-Maskawa (CKM) Unitarity Triangle using a time-dependent Dalitz plot analysis of B^{0}→D^{(*)}h^{0} with D→K_{S}^{0}π^{+}π^{-} decays, where h^{0}∈{π^{0},η,ω} denotes a light unflavored and neutral hadron. The measurement is performed combining the final data sets of the BABAR and Belle experiments collected at the ϒ(4S) resonance at the asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. The data samples contain (471±3)×10^{6}BB[over ¯] pairs recorded by the BABAR detector and (772±11)×10^{6}BB[over ¯] p…

Measurement of the production cross section forZ/γ*in association with jets inppcollisions ats=7  TeVwith the ATLAS detector

2012

Results are presented on the production of jets of particles in association with a Z/gamma* boson, in proton-proton collisions at root s = 7 TeV with the ATLAS detector. The analysis includes the full 2010 data set, collected with a low rate of multiple proton-proton collisions in the accelerator, corresponding to an integrated luminosity of 36 pb(-1). Inclusive jet cross sections in Z/gamma* events, with Z/gamma* decaying into electron or muon pairs, are measured for jets with transverse momentum p(T) > 30 GeV and jet rapidity vertical bar y vertical bar < 4.4. The measurements are compared to next-to-leading-order perturbative QCD calculations, and to predictions from different Monte Carl…

Measurement of the production cross section of an isolated photon associated with jets in proton-proton collisions ats=7  TeVwith the ATLAS detector

2012

A measurement of the cross section for the production of an isolated photon in association with jets in proton-proton collisions at a center-of-mass energy root s = 7 TeV is presented. Photons are ...

Search for the supersymmetric partner of the top quark inpp¯collisions ats=1.96  TeV

2010

We present a search for the lightest supersymmetric partner of the top quark in proton-antiproton collisions at a center-of-mass energy root s = 1: 96 TeV. This search was conducted within the framework of the R parity conserving minimal supersymmetric extension of the standard model, assuming the stop decays dominantly to a lepton, a sneutrino, and a bottom quark. We searched for events with two oppositely-charged leptons, at least one jet, and missing transverse energy in a data sample corresponding to an integrated luminosity of 1 fb(-1) collected by the Collider Detector at Fermilab experiment. No significant evidence of a stop quark signal was found. Exclusion limits at 95% confidence …

Further search for supersymmetry ats=7  TeVin final states with jets, missing transverse momentum, and isolated leptons with the ATLAS detector

2012

This work presents a new inclusive search for supersymmetry (SUSY) by the ATLAS experiment at the LHC in proton-proton collisions at a center-of-mass energy root s = 7 TeV in final states with jets, missing transverse momentum and one or more isolated electrons and/or muons. The search is based on data from the full 2011 data-taking period, corresponding to an integrated luminosity of 4.7 fb(-1). Single-lepton and multilepton channels are treated together in one analysis. An increase in sensitivity is obtained by simultaneously fitting the number of events in statistically independent signal regions, and the shapes of distributions within those regions. A dedicated signal region is introduc…

Measurement of the correlation between flow harmonics of different order in lead-lead collisions at sNN=2.76 TeV with the ATLAS detector

2015

Correlations between the elliptic or triangular flow coefficients v(m) (m = 2 or 3) and other flow harmonics v(n) (n = 2 to 5) are measured using root S-NN = 2.76 TeV Pb + Pb collision data collected in 2010 by the ATLAS experiment at the LHC, corresponding to an integrated luminosity of 7 mu b(-1). The v(m)-v(n) correlations aremeasured in midrapidity as a function of centrality, and, for events within the same centrality interval, as a function of event ellipticity or triangularity defined in a forward rapidity region. For events within the same centrality interval, v(3) is found to be anticorrelated with v(2) and this anticorrelation is consistent with similar anticorrelations between th…

Search for a Light Higgs Boson Decaying to Long-Lived Weakly Interacting Particles in Proton-Proton Collisions ats=7  TeVwith the ATLAS Detector

2012

A search for the decay of a light Higgs boson (120-140 GeV) to a pair of weakly interacting, long-lived particles in 1.94 fb(-1) of proton-proton collisions at root s = 7 TeV recorded in 2011 by the ATLAS detector is presented. The search strategy requires that both long-lived particles decay inside the muon spectrometer. No excess of events is observed above the expected background and limits on the Higgs boson production times branching ratio to weakly interacting, long-lived particles are derived as a function of the particle proper decay length.

Production ofΛ0,Λ¯0,Ξ±, andΩ±hyperons inpp¯collisions ats=1.96  TeV

2012

We report a set of measurements of inclusive invariant ${p}_{T}$ differential cross sections of ${\ensuremath{\Lambda}}^{0}$, ${\overline{\ensuremath{\Lambda}}}^{0}$, ${\ensuremath{\Xi}}^{\ifmmode\pm\else\textpm\fi{}}$, and ${\ensuremath{\Omega}}^{\ifmmode\pm\else\textpm\fi{}}$ hyperons reconstructed in the central region with pseudorapidity $|\ensuremath{\eta}|l1$ and ${p}_{T}$ up to $10\text{ }\text{ }\mathrm{GeV}/c$. Events are collected with a minimum-bias trigger in $p\overline{p}$ collisions at a center-of-mass energy of 1.96 TeV using the CDF II detector at the Tevatron Collider. As ${p}_{T}$ increases, the slopes of the differential cross sections of the three particles are similar,…

Drift Time Measurement in the ATLAS Liquid Argon Electromagnetic Calorimeter using Cosmic Muons

2010

The ionization signals in the liquid argon of the ATLAS electromagnetic calorimeter are studied in detail using cosmic muons. In particular, the drift time of the ionization electrons is measured and used to assess the intrinsic uniformity of the calorimeter gaps and estimate its impact on the constant term of the energy resolution. The drift times of electrons in the cells of the second layer of the calorimeter are uniform at the level of 1.3% in the barrel and 2.8% in the endcaps. This leads to an estimated contribution to the constant term of (0.29-0.04+0.05)% in the barrel and (0.54-0.04+0.06)% in the endcaps. The same data are used to measure the drift velocity of ionization electrons …

Measurement of the W boson polarization in top quark decays with the ATLAS detector

2012

This paper presents measurements of the polarization of W bosons in top quark decays, derived from t¯t events with missing transverse momentum, one charged lepton and at least four jets, or two charged leptons and at least two jets. Data from pp collisions at a centre-of-mass energy of 7 TeV were collected with the ATLAS experiment at the LHC and correspond to an integrated luminosity of 1.04 fb−1. The measured fractions of longitudinally, left- and right-handed polarization are F0 = 0.67 ± 0.07, FL = 0.32 ± 0.04 and FR = 0.01 ± 0.05, in agreement with the Standard Model predictions. As the polarization of the W bosons in top quark decays is sensitive to the Wtb vertex Lorentz structure and…

Measurement of theCP-violating phaseβsJ/ψϕinBs0→J/ψϕdecays with the CDF II detector

2012

We present a measurement of the \CP-violating parameter \betas using approximately 6500 $$\BsJpsiPhi$$ decays reconstructed with the CDF\,II detector in a sample of $$p\bar p$$ collisions at $$\sqrt{s}=1.96$$ TeV corresponding to 5.2 fb$$^{-1}$$ integrated luminosity produced by the Tevatron Collider at Fermilab. We find the \CP-violating phase to be within the range $$\betas \in [0.02, 0.52] \cup [1.08, 1.55]$$ at 68% confidence level where the coverage property of the quoted interval is guaranteed using a frequentist statistical analysis. This result is in agreement with the standard model expectation at the level of about one Gaussian standard deviation. We consider the inclusion of a po…

Charge separation relative to the reaction plane in Pb-Pb collisions atsNN=2.76  TeV

2013

Measurements of charge-dependent azimuthal correlations with the ALICE detector at the LHC are reported for Pb-Pb collisions at root s(NN) = 2.76 TeV. Two- and three-particle charge-dependent azimuthal correlations in the pseudorapidity range vertical bar eta vertical bar < 0.8 are presented as a function of the collision centrality, particle separation in pseudorapidity, and transverse momentum. A clear signal compatible with a charge-dependent separation relative to the reaction plane is observed, which shows little or no collision energy dependence when compared to measurements at RHIC energies. This provides a new insight for understanding the nature of the charge-dependent azimuthal co…

Status of the J-PARC E07, Systematic Study of Double Strangeness Nuclei with the Hybrid Emulsion Method

2019

The current status of the J-PARC E07 experiment and two typical events, a _ΛΛBe hypernuclear event named “MINO” and \(_{\Xi }^{15}\text{C}\) hypernuclear event named “IBUKI”, are presented. J-PARC E07 is the most complex emulsion experiment so far to investigate double hypernuclei. The physics run at the K1.8 beam line in the J-PARC hadron facility and photographic development of all emulsion sheets have been completed. The emulsion sheets are presently being analyzed with dedicated optical microscopes. Current statistics are estimated to be about twice that of KEK-PS E373. Quantitative data on ΔB_ΛΛ of double Λ hypernucleus and \(B_{\Xi ^{ - }}\) of Ξ hypernucleus are being accumulated suc…

A measurement of material in the ATLAS tracker using secondary hadronic interactions in 7 TeV pp collisions

2016

Knowledge of the material in the ATLAS inner tracking detector is crucial in understanding the reconstruction of charged-particle tracks, the performance of algorithms that identify jets containing b-hadrons and is also essential to reduce background in searches for exotic particles that can decay within the inner detector volume. Interactions of primary hadrons produced in pp collisions with the material in the inner detector are used to map the location and amount of this material. The hadronic interactions of primary particles may result in secondary vertices, which in this analysis are reconstructed by an inclusive vertex-finding algorithm. Data were collected using minimum-bias trigger…

Measurement of the jet fragmentation function and transverse profile in proton-proton collisions at a center-of-mass energy of 7 TeV with the ATLAS d…

2011

The jet fragmentation function and transverse profile for jets with 25 GeV<pT jet<500 GeV and |ηjet|<1.2 produced in proton–proton collisions with a center-of-mass energy of 7 TeV are presented. The measurement is performed using data with an integrated luminosity of 36 pb−1. Jets are reconstructed and their momentum measured using calorimetric information. The momenta of the charged particle constituents are measured using the tracking system. The distributions corrected for detector effects are compared with various Monte Carlo event generators and generator tunes. Several of these choices show good agreement with the measured fragmentation function. None of these choices reproduce both t…

Search for heavy neutrinos and right-handed W bosons in events with two leptons and jets in pp collisions at √s=7 TeV with the ATLAS detector

2012

This letter reports on a search for hypothetical heavy neutrinos, N, and right-handed gauge bosons, WR, in events with high transverse momentum objects which include two reconstructed leptons and at least one hadronic jet. The results were obtained from data corresponding to an integrated luminosity of 2.1 fb−1 collected in proton–proton collisions at √s=7 TeV with the ATLAS detector at the CERN Large Hadron Collider. No excess above the Standard Model background expectation is observed. Excluded mass regions for Majorana and Dirac neutrinos are presented using two approaches for interactions that violate lepton and lepton-flavor numbers. One approach uses an effective operator framework, t…

Search for Dark Matter in Events with Missing Transverse Momentum and a Higgs Boson Decaying to Two Photons inppCollisions ats=8  TeVwith the ATLAS D…

2015

Results of a search for new phenomena in events with large missing transverse momentum and a Higgs boson decaying to two photons are reported. Data from proton-proton collisions at a center-of-mass energy of 8 TeV and corresponding to an integrated luminosity of 20.3  fb−1 have been collected with the ATLAS detector at the LHC. The observed data are well described by the expected standard model backgrounds. Upper limits on the cross section of events with large missing transverse momentum and a Higgs boson candidate are also placed. Exclusion limits are presented for models of physics beyond the standard model featuring dark-matter candidates.

Direct Top-Quark Width Measurement at CDF

2010

7 páginas, 2 figuras, 2 tablas.-- CDF Collaboration: et al.

Search for resonances in the mass distribution of jet pairs with one or two jets identified as b-jets in proton–proton collisions at s=13 TeV with th…

2016

Searches for high-mass resonances in the dijet invariant mass spectrum with one or two jets identified as $b$-jets are performed using an integrated luminosity of $3.2$ fb$^{-1}$ of proton--proton collisions with a centre-of-mass energy of $\sqrt{s}=13$ TeV recorded by the ATLAS detector at the Large Hadron Collider. No evidence of anomalous phenomena is observed in the data, which are used to exclude, at 95% credibility level, excited $b^{*}$ quarks with masses from 1.1 TeV to 2.1 TeV and leptophobic $Z'$ bosons with masses from 1.1 TeV to 1.5 TeV. Contributions of a Gaussian signal shape with effective cross sections ranging from approximately 0.4 to 0.001 pb are also excluded in the mass…

Search for heavy resonances decaying to a photon and a hadronically decaying Z/W/H boson in pp collisions at s=13  TeV with the ATLAS detector

2018

This Letter presents a search for the production of new heavy resonances decaying into a Higgs boson and a photon using proton-proton collision data at √ s = 13     TeV collected by the ATLAS detector at the LHC. The data correspond to an integrated luminosity of 139     fb − 1 . The analysis is performed by reconstructing hadronically decaying Higgs boson ( H → b ¯ b ) candidates as single large-radius jets. A novel algorithm using information about the jet constituents in the center-of-mass frame of the jet is implemented to identify the two b quarks in the single jet. No significant excess of events is observed above the expected background. Upper limits are set on the production cross-s…

Search for Higgs bosons produced via vector-boson fusion and decaying into bottom quark pairs in s=13  TeV pp collisions with the ATLAS detector

2018

A search for the b (b) over bar decay of the Standard Model Higgs boson produced through vector-boson fusion is presented. Three mutually exclusive channels are considered: two all-hadronic channel ...

SARS-CoV-2 vaccination modelling for safe surgery to save lives: data from an international prospective cohort study

2021

Abstract Background Preoperative SARS-CoV-2 vaccination could support safer elective surgery. Vaccine numbers are limited so this study aimed to inform their prioritization by modelling. Methods The primary outcome was the number needed to vaccinate (NNV) to prevent one COVID-19-related death in 1 year. NNVs were based on postoperative SARS-CoV-2 rates and mortality in an international cohort study (surgical patients), and community SARS-CoV-2 incidence and case fatality data (general population). NNV estimates were stratified by age (18–49, 50–69, 70 or more years) and type of surgery. Best- and worst-case scenarios were used to describe uncertainty. Results NNVs were more favourable in su…

Measurement of isolated-photon pair production in pp collisions at root s=7 TeV with the ATLAS detector

2013

The ATLAS experiment at the LHC has measured the production cross section of events with two isolated photons in the final state, in proton-proton collisions at √s = 7 TeV . The full data set collected in 2011, corresponding to an integrated luminosity of 4.9 fb[superscript −1], is used. The amount of background, from hadronic jets and isolated electrons, is estimated with data-driven techniques and subtracted. The total cross section, for two isolated photons with transverse energies above 25 GeV and 22 GeV respectively, in the acceptance of the electromagnetic calorimeter (|η|  0.4, is 44.0[+3.2 over −4.2] pb. The differential cross sections as a function of the di-photon invariant mass, …

Observation of Orbitally Excited Bs Mesons

2007

We report the first observation of two narrow resonances consistent with states of orbitally excited (L=1) B_s mesons using 1 fb^{-1} of ppbar collisions at sqrt{s} = 1.96 TeV collected with the CDF II detector at the Fermilab Tevatron. We use two-body decays into K^- and B^+ mesons reconstructed as B^+ \to J/\psi K^+, J/\psi \to \mu^+ \mu^- or B^+ \to \bar{D}^0 \pi^+, \bar{D}^0 \to K^+ \pi^-. We deduce the masses of the two states to be m(B_{s1}) = 5829.4 +- 0.7 MeV/c^2 and m(B_{s2}^*) = 5839.7 +- 0.7 MeV/c^2.

Search for Production of Resonant States in the Photon-Jet Mass Distribution UsingppCollisions ats=7  TeVCollected by the ATLAS Detector

2012

This Letter describes a model-independent search for the production of new resonant states in photon + jet events in 2.11 fb(-1) of proton-proton collisions at root s = 7 TeV. We compare the photon ...

J/ψSuppression at Forward Rapidity in Pb-Pb Collisions atsNN=2.76  TeV

2012

The ALICE experiment has measured the inclusive J/psi production in Pb-Pb collisions at root s(NN) = 2.76 TeV down to zero transverse momentum in the rapidity range 2.5 < y < 4. A suppression of the inclusive J/psi yield in Pb-Pb is observed with respect to the one measured in pp collisions scaled by the number of binary nucleon-nucleon collisions. The nuclear modification factor, integrated over the 0%-80% most central collisions, is 0.545 +/- 0.032(stat) +/- 0.083dsyst_ and does not exhibit a significant dependence on the collision centrality. These features appear significantly different from measurements at lower collision energies. Models including J/psi production from charm quarks in…

Combination of CDF and D0 W-Boson mass measurements

2013

We summarize and combine direct measurements of the mass of the W boson in √s=1.96 TeV proton-antiproton collision data collected by CDF and D0 experiments at the Fermilab Tevatron Collider. Earlier measurements from CDF and D0 are combined with the two latest, more precise measurements: a CDF measurement in the electron and muon channels using data corresponding to 2.2 fb-1 of integrated luminosity, and a D0 measurement in the electron channel using data corresponding to 4.3 fb-1 of integrated luminosity. The resulting Tevatron average for the mass of the W boson is M W=80387±16 MeV. Including measurements obtained in electron-positron collisions at LEP yields the most precise value of M W…

Measurements of Higgs boson production and couplings in the four-lepton channel inppcollisions at center-of-mass energies of 7 and 8 TeV with the ATL…

2015

The final ATLAS Run 1 measurements of Higgs boson production and couplings in the decay channel H -> ZZ* -> l(+)l(-)l(+)l'(-), where l, l' = e or mu, are presented. These measurements were performed using pp collision data corresponding to integrated luminosities of 4.5 and 20.3 fb(-1) at center-of-mass energies of 7 and 8 TeV, respectively, recorded with the ATLAS detector at the LHC. The H -> ZZ* -> 4l signal is observed with a significance of 8.1 standard deviations, with an expectation of 6.2 standard deviations, at m(H) = 125.36 GeV, the combined ATLAS measurement of the Higgs boson mass from the H -> gamma gamma and H -> ZZ* -> 4l channels. The production rate relative to the Standard…

Measurement of the high-mass Drell–Yan differential cross-section in pp collisions at s=7 TeV with the ATLAS detector

2013

This Letter reports a measurement of the high-mass Drell–Yan differential cross-section in proton–proton collisions at a centre-of-mass energy of 7 TeV at the LHC. Based on an integrated luminosity ...

Search for new phenomena in dijet events using 37  fb−1 of pp collision data collected at s=13  TeV with the ATLAS detector

2017

Dijet events are studied in the proton-proton collision dataset recorded at root s = 13 TeV with the ATLAS detector at the Large Hadron Collider in 2015 and 2016, corresponding to integrated lumino ...

Measurement of the suppression and azimuthal anisotropy of muons from heavy-flavor decays in Pb+Pb collisions at sNN=2.76 TeV with the ATLAS detector

2018

ATLAS measurements of the production of muons from heavy-flavor decays in root s(NN) = 2.76 TeV Pb+Pb collisions and root s = 2.76 TeV pp collisions at the LHC are presented. Integrated luminositie ...

Search for Higgs andZBoson Decays toJ/ψγandϒ(nS)γwith the ATLAS Detector

2015

A search for the decays of the Higgs and Z bosons to J/psi gamma and Upsilon(nS)gamma (n = 1,2,3) is performed with pp collision data samples corresponding to integrated luminosities of up to 20.3 fb(-1) collected at root s = 8 TeV with the ATLAS detector at the CERN Large Hadron Collider. No significant excess of events is observed above expected backgrounds and 95% C.L. upper limits are placed on the branching fractions. In the J/psi gamma final state the limits are 1.5 x 10(-3) and 2.6 x 10(-6) for the Higgs and Z boson decays, respectively, while in the Upsilon(1S, 2S, 3S)gamma. final states the limits are (1.3, 1.9, 1.3) x 10(-3) and (3.4, 6.5, 5.4) x 10(-6), respectively.

Search for Large Extra Dimensions in Final States Containing One Photon or Jet and Large Missing Transverse Energy Produced inpp¯Collisions ats=1.96 …

2008

We present the results of searches for large extra dimensions in samples of events with large missing transverse energy E_{T} and either a photon or a jet produced in pp[over ] collisions at sqrt[s]=1.96 TeV collected with the Collider Detector at Fermilab II. For gamma+E_{T} and jet+E_{T} candidate samples corresponding to 2.0 and 1.1 fb;{-1} of integrated luminosity, respectively, we observe good agreement with standard model expectations and obtain a combined lower limit on the fundamental parameter of the large extra dimensions model M_{D} as a function of the number of extra dimensions in the model.

Search for the DecaysB(s)0→e+μ−andB(s)0→e+e−in CDF Run II

2009

We report results from a search for the lepton flavor violating decays $B^0_{(s)}\to e^+\mu^-$, and the flavor-changing neutral-current decays $B^0_{(s)} \to e^+ e^-$. The analysis uses data corresponding to ${\rm 2 fb^{-1}}$ of integrated luminosity of $p \bar{p}$ collisions at $\sqrt{s}=1.96 {\rm TeV}$ collected with the upgraded Collider Detector (CDF II) at the Fermilab Tevatron. The observed number of $B^0_{(s)}$ candidates is consistent with background expectations. The resulting Bayesian upper limits on the branching ratios at 90% credibility level are $\mathcal{B}(B^0_s \to e^{+}\mu^{-}) 47.8 {\rm TeV/c^2}$, and ${M_{LQ}}(B^0\to e^+ \mu^-) > 59.3 {\rm TeV/c^2}$, at 90% credibility l…

Measurement of Top Quark Polarization in Top-Antitop Events from Proton-Proton Collisions ats=7  TeVUsing the ATLAS Detector

2013

This Letter presents measurements of the polarization of the top quark in top-antitop quark pair events, using 4: 7 fb(-1) of proton-proton collision data recorded with the ATLAS detector at the La ...

Search for a Higgs Boson Decaying to Two W Bosons at CDF

2008

We present a search for a Higgs boson decaying to two W bosons in p (p) over bar collisions at root s = 1.96 TeV center-of-mass energy. The data sample corresponds to an integrated luminosity of 3.0 fb(-1) collected with the CDF II detector. We find no evidence for production of a Higgs boson with mass between 110 and 200 GeV/c(2), and determine upper limits on the production cross section. For the mass of 160 GeV/c(2), where the analysis is most sensitive, the observed (expected) limit is 0.7 pb (0.9 pb) at 95% Bayesian credibility level which is 1.7 (2.2) times the standard model cross section.

Properties of jets measured from tracks in proton-proton collisions at center-of-mass energys=7  TeVwith the ATLAS detector

2011

Jets are identified and their properties studied in center-of-mass energy root s = 7 TeV proton-proton collisions at the Large Hadron Collider using charged particles measured by the ATLAS inner detector. Events are selected using a minimum bias trigger, allowing jets at very low transverse momentum to be observed and their characteristics in the transition to high-momentum fully perturbative jets to be studied. Jets are reconstructed using the anti-k(t) algorithm applied to charged particles with two radius parameter choices, 0.4 and 0.6. An inclusive charged jet transverse momentum cross section measurement from 4 GeV to 100 GeV is shown for four ranges in rapidity extending to 1.9 and co…

Observation of Spin Correlation intt¯Events fromppCollisions ats=7  TeVUsing the ATLAS Detector

2012

A measurement of spin correlation in t (t) over bar production is reported using data collected with the ATLAS detector at the LHC, corresponding to an integrated luminosity of 2.1 fb(-1). Candidat ...

Limits on anomalous triple gauge couplings inpp¯collisions ats=1.96  TeV

2007

We present a search for anomalous triple gauge couplings (ATGC) in WW and WZ boson production. The boson pairs are produced in p (p) over bar collisions at root s = 1.96 TeV, and the data sample corresponds to 350 pb(-1) of integrated luminosity collected with the CDF II detector at the Fermilab Tevatron. In this search one W decays to leptons, and the other boson (W or Z) decays hadronically. Combining with a previously published CDF measurement of W gamma boson production yields ATGC limits of -0.18 <lambda < 0.17 and -0.46 <Delta kappa < 0.39 at the 95% confidence level, using a cutoff scale Lambda=1.5 TeV.

Search for third generation scalar leptoquarks in pp collisions at √s = 7 TeV with the ATLAS detector

2013

A search for pair-produced third generation scalar leptoquarks is presented, using proton-proton collisions at √s = 7 TeV at the LHC. The data were recorded with the ATLAS detector and correspond to an integrated luminosity of 4.7 fb[superscript −1]. Each leptoquark is assumed to decay to a tau lepton and a b-quark with a branching fraction equal to 100%. No statistically significant excess above the Standard Model expectation is observed. Third generation leptoquarks are therefore excluded at 95% confidence level for masses less than 534 GeV.

Measurement of Spin Correlation in Top-Antitop Quark Events and Search for Top Squark Pair Production inppCollisions ats=8  TeVUsing the ATLAS Detect…

2015

A measurement of spin correlation in t (t) over bar production is presented using data collected with the ATLAS detector at the Large Hadron Collider in proton-proton collisions at a center-of-mass ...

Comprehensive measurements oft-channel single top-quark production cross sections ats=7  TeVwith the ATLAS detector

2014

This article presents measurements of the t-channel single top-quark ((t) over bart) and top-antiquark (_ t) total production cross sections sdtq_ and sd _ tq_, their ratio Rt sdtq_= sd _ tq_, and a measurement of the inclusive production cross section sdtq _ _ tq_ in proton-proton collisions at ffiffiffi ps = 7 TeV at the LHC. Differential cross sections for the tq and _ tq processes are measured as a function of the transverse momentum and the absolute value of the rapidity of t and _ t, respectively. The analyzed data set was recorded with the ATLAS detector and corresponds to an integrated luminosity of 4.59 fb-1. Selected events contain one charged lepton, large missing transverse mome…

Search for lepton flavour violation in the e mu continuum with the ATLAS detector in root s=7 TeV pp collisions at the LHC

2012

This paper presents a search for the t-channel exchange of an R-parity violating scalar top quark ([~ over t] ) in the e[superscript ±]μ[superscript ∓] continuum using 2.1 fb[superscript −1] of data collected by the ATLAS detector in s√=7 TeV pp collisions at the Large Hadron Collider. Data are found to be consistent with the expectation from the Standard Model backgrounds. Limits on R-parity-violating couplings at 95 % C.L. are calculated as a function of the scalar top mass ( m[subscript bar over t]). The upper limits on the production cross section for pp→eμX, through the t-channel exchange of a scalar top quark, ranges from 170 fb for m[subscript ~ over t]=95 GeV to 30 fb for m[subscrip…

Search for heavy vector-like quarks coupling to light quarks in proton–proton collisions at s=7 TeV with the ATLAS detector

2012

This letter presents a search for singly produced vector-like quarks, Q, coupling to light quarks, q. The search is sensitive to both charged current (CC) and neutral current (NC) processes, p p --> Q q --> W q q' and p p --> Q q --> Z q q' with a leptonic decay of the vector gauge boson. In 1.04/fb of data taken in 2011 by the ATLAS experiment at a center-of-mass energy sqrt(s) = 7 TeV, no evidence of such heavy vector-like quarks is observed above the expected Standard Model background. Limits on the heavy vector-like quark production cross section times branching ratio as a function of mass m_Q are obtained. For a coupling kappa_(qQ) = v/m_Q, where v is the Higgs vacuum expectation value…

Search for contact interactions in dimuon events fromppcollisions ats=7  TeVwith the ATLAS detector

2011

A search for contact interactions has been performed using dimuon events recorded with the ATLAS detector in proton-proton collisions at root s = 7 TeV. The data sample corresponds to an integrated ...

Measurement of the top quark mass in the dilepton channel using mT2 at CDF

2010

We present measurements of the top quark mass using mT2, a variable related to the transverse mass in events with two missing particles. We use the template method applied to tt̅ dilepton events produced in pp̅ collisions at Fermilab’s Tevatron Collider and collected by the CDF detector. From a data sample corresponding to an integrated luminosity of 3.4  fb-1, we select 236 tt̅ candidate events. Using the mT2 distribution, we measure the top quark mass to be Mtop=168.0-4.0+4.8(stat)±2.9(syst)  GeV/c2. By combining mT2 with the reconstructed top quark mass distributions based on a neutrino weighting method, we measure Mtop=169.3±2.7(stat)±3.2(syst)  GeV/c2. This is the first application of …

Charged-particle multiplicities in pp interactions measured with the ATLAS detector at the LHC

2011

Measurements are presented from proton–proton collisions at centre-of-mass energies of \sqrt{s} = 0.9 , 2.36 and 7 TeV recorded with the ATLAS detector at the LHC. Events were collected using a single-arm minimum-bias trigger. The charged-particle multiplicity, its dependence on transverse momentum and pseudorapidity and the relationship between the mean transverse momentum and charged-particle multiplicity are measured. Measurements in different regions of phase space are shown, providing diffraction-reduced measurements as well as more inclusive ones. The observed distributions are corrected to well-defined phase-space regions, using model-independent corrections. The results are compared…

Readiness of the ATLAS Tile Calorimeter for LHC collisions

2010

67 páginas.-- El PDF es la versión pre-print (arXiv:1007.5423v2).-- The ATLAS Collaboration.-- et al.

Search for Higgs andZBoson Decays toϕγwith the ATLAS Detector

2016

A search for the decays of the Higgs and Z bosons to a ϕ meson and a photon is performed with a pp collision data sample corresponding to an integrated luminosity of 2.7  fb^{-1} collected at sqrt[s]=13  TeV with the ATLAS detector at the LHC. No significant excess of events is observed above the background, and 95% confidence level upper limits on the branching fractions of the Higgs and Z boson decays to ϕγ of 1.4×10^{-3} and 8.3×10^{-6}, respectively, are obtained.

Search for Maximal Flavor Violating Scalars in Same-Charge Lepton Pairs inpp¯Collisions ats=1.96  TeV

2009

Models of maximal flavor violation (MxFV) in elementary particle physics may contain at least one new scalar SU(2) doublet field {phi}{sub FV}=({eta}{sup 0},{eta}{sup +}) that couples the first and third generation quarks (q{sub 1}, q{sub 3}) via a Lagrangian term L{sub FV}={xi}{sub 13}{phi}{sub FV}q{sub 1}q{sub 3}. These models have a distinctive signature of same-charge top-quark pairs and evade flavor-changing limits from meson mixing measurements. Data corresponding to 2 fb{sup -1} collected by the Collider Dectector at Fermilab II detector in pp collisions at {radical}(s)=1.96 TeV are analyzed for evidence of the MxFV signature. For a neutral scalar {eta}{sup 0} with m{sub {eta}{sup 0}…

Measurement of the W±Z production cross section and limits on anomalous triple gauge couplings in proton–proton collisions at s=7 TeV with the ATLAS …

2012

This Letter presents a measurement of W(+/-)Z production in 1.02 fb(-1) of pp collision data at root s = 7 TeV collected by the ATLAS experiment in 2011. Doubly leptonic decay events are selected w ...

Measurement of the inclusive jet cross-section in pp collisions at $\sqrt{s}=2.76\ \mbox{TeV}$ and comparison to the inclusive jet cross-section at $…

2013

The inclusive jet cross-section has been measured in proton-proton collisions at sqrt(s)=2.76 TeV in a dataset corresponding to an integrated luminosity of 0.20pb-1 collected with the ATLAS detector at the Large Hadron Collider in 2011. Jets are identified using the anti-kt algorithm with two radius parameters of 0.4 and 0.6. The inclusive jet double-differential cross-section is presented as a function of the jet transverse momentum pT and jet rapidity y, covering a range of 20 &lt;= pT &lt; 430 GeV and |y| &lt; 4.4. The ratio of the cross-section to the inclusive jet cross-section measurement at sqrt(s)=7 TeV, published by the ATLAS Collaboration, is calculated as a function of both trans…

Measurement of the correlation between the polar angles of leptons from top quark decays in the helicity basis ats=7  TeVusing the ATLAS detector

2016

A measurement of the correlations between the polar angles of leptons from the decay of pair-produced t and (t) over bar quarks in the helicity basis is reported, using proton-proton collision data collected by the ATLAS detector at the LHC. The dataset corresponds to an integrated luminosity of 4.6 fb(-1) at a center-of-mass energy of root s = 7 TeV collected during 2011. Candidate events are selected in the dilepton topology with large missing transverse momentum and at least two jets. The angles theta(1) and theta(2) between the charged leptons and the direction of motion of the parent quarks in the t (t) over bar rest frame are sensitive to the spin information, and the distribution of …

Search for top and bottom squarks from gluino pair production in final states with missing transverse energy and at least three b-jets with the ATLAS…

2012

This letter reports the results of a search for top and bottom squarks from gluino pair production in 4.7 fb[superscript −1] of pp collisions at s√=7 TeV using the ATLAS detector at the LHC. The search is performed in events with large missing transverse momentum and at least three jets identified as originating from a b-quark. Exclusion limits are presented for a variety of gluino-mediated models with gluino masses up to 1 TeV excluded.

Search for the Higgs Boson in Events with Missing Transverse Energy andbQuark Jets Produced inpp¯Collisions ats=1.96  TeV

2008

We search for the standard model Higgs boson produced in association with an electroweak vector boson in events with no identified charged leptons, large imbalance in transverse momentum, and two jets where at least one contains a secondary vertex consistent with the decay of b hadrons. We use {approx}1 fb{sup -1} integrated luminosity of p{bar p} collisions at {radical}s = 1.96 TeV recorded by the CDF II experiment at the Tevatron. We find 268 (16) single (double) b-tagged candidate events, where 248 {+-} 43 (14.4 {+-} 2.7) are expected from standard model background processes. We place 95% confidence level upper limits on the Higgs boson production cross section for several Higgs boson ma…

Tevatron Combination of Single-Top-Quark Cross Sections and Determination of the Magnitude of the Cabibbo-Kobayashi-Maskawa Matrix Element Vtb

2015

et al.

J/ψ production as a function of charged particle multiplicity in pp collisions at s =7 TeV

2012

The ALICE Collaboration reports the measurement of the relative J/psi yield as a function of charged particle pseudorapidity density dN(ch)/d eta in pp collisions at root s = 7 TeV at the LHC. J/psi particles are detected for p(t) > 0, in the rapidity interval vertical bar y vertical bar 0. In the highest multiplicity interval with (dN(ch)/d eta)(bin)) = 24.1, corresponding to four times the minimum bias multiplicity density, an enhancement relative to the minimum bias J/psi yield by a factor of about 5 at 2.5 < y <4 (8 at vertical bar y vertical bar < 0.9) is observed. (C) 2012 CERN. Published by Elsevier B.V. All rights reserved.

Alignment of the ALICE Inner Tracking System with cosmic-ray tracks

2010

ALICE (A Large Ion Collider Experiment) is the LHC (Large Hadron Collider) experiment devoted to investigating the strongly interacting matter created in nucleus-nucleus collisions at the LHC energies. The ALICE ITS, Inner Tracking System, consists of six cylindrical layers of silicon detectors with three different technologies; in the outward direction: two layers of pixel detectors, two layers each of drift, and strip detectors. The number of parameters to be determined in the spatial alignment of the 2198 sensor modules of the ITS is about 13,000. The target alignment precision is well below 10 micron in some cases (pixels). The sources of alignment information include survey measurement…

Search for anomalous production of events with two photons and additional energetic objects at CDF

2010

27 páginas, 17 figuras, 5 tablas.-- CDF Collaboration: et al.

Inclusive Search for Squark and Gluino Production inpp¯Collisions ats=1.96  TeV

2009

We report on a search for inclusive production of squarks and gluinos in p{bar p} collisions at {radical}s = 1.96 TeV, in events with large missing transverse energy and multiple jets of hadrons in the final state. The study uses a CDF Run II data sample corresponding to 2 fb-1 of integrated luminosity. The data are in good agreement with the standard model predictions, giving no evidence for any squark or gluino component. In an R-parity conserving minimal supergravity scenario with A{sub 0} = 0, mu < 0 and tan beta = 5, 95% C.L. upper limits on the production cross sections in the range between 0.1 pb and 1 pb are obtained, depending on the squark and gluino masses considered. For gluino …

Light vector meson production in pp collisions at s=7 TeV

2012

The ALICE experiment has measured low-mass dimuon production in pp collisions at root s = 7 TeV in the dimuon rapidity region 2.5 < y < 4. The observed dimuon mass spectrum is described as a superposition of resonance decays (eta, rho, omega, eta', phi) into muons and semi-leptonic decays of charmed mesons. The measured production cross sections for omega and phi are sigma(omega)(1 < p(t) < 5 GeV/c. 2.5 < y < 4) = 5.28 +/- 0.54(stat) +/- 0.49(syst) mb and sigma(phi)(1 < p(t) < 5 GeV/c. 2.5 < y < 4) = 0.940 +/- 0.084(stat) +/- 0.076(syst) mb. The differential cross sections d(2)sigma/dy dp(t) are extracted as a function of p(t) for omega and phi. The ratio between the rho and omega cross sec…

Search for same-sign top-quark production and fourth-generation down-type quarks in pp collisions at √s = 7 TeV with the ATLAS detector

2012

A search is presented for same-sign top-quark production and down-type heavy quarks of charge −1/3 in events with two isolated leptons (e or μ) that have the same electric charge, at least two jets and large missing transverse momentum. The data are selected from pp collisions at √s=7TeV recorded by the ATLAS detector and correspond to an integrated luminosity of 1.04 fb−1. The observed data are consistent with expectations from Standard Model processes. Upper limits are set at 95 % confidence level on the cross section of new sources of same-sign top-quark pair production of 1.4-2.0 pb depending on the assumed mediator mass. Upper limits are also set on the pair-production cross-section fo…

Forward-backward correlations and charged-particle azimuthal distributions in $pp$ interactions using the ATLAS detector

2012

Using inelastic proton-proton interactions at sqrt(s) = 900 GeV and 7 TeV, recorded by the ATLAS detector at the LHC, measurements have been made of the correlations between forward and backward charged-particle multiplicities and, for the first time, between forward and backward charged-particle summed transverse momentum. In addition, jet-like structure in the events is studied by means of azimuthal distributions of charged particles relative to the charged particle with highest transverse momentum in a selected kinematic region of the event. The results are compared with predictions from tunes of the PYTHIA and HERWIG++ Monte Carlo generators, which in most cases are found to provide a r…

Search for the Higgs Boson Using Neural Networks in Events with Missing Energy andb-Quark Jets inpp¯Collisions ats=1.96  TeV

2010

We report on a search for the standard model Higgs boson produced in association with a W or Z boson in p{bar p} collisions at {radical}s = 1.96 TeV recorded by the CDF II experiment at the Tevatron in a data sample corresponding to an integrated luminosity of 2.1 fb{sup -1}. We consider events which have no identified charged leptons, an imbalance in transverse momentum, and two or three jets where at least one jet is consistent with originating from the decay of a b hadron. We find good agreement between data and predictions. We place 95% confidence level upper limits on the production cross section for several Higgs boson masses ranging from 110 GeV/c{sup 2} to 150 GeV/c{sup 2}. For a ma…

Search for type-III seesaw heavy leptons inppcollisions ats=8  TeVwith the ATLAS detector

2015

A search for the pair production of heavy leptons (N-0, L-+/-) predicted by the type-III seesaw theory formulated to explain the origin of small neutrino masses is presented. The decay channels N-0 -> W(+/-)l(+/-) (l = e, mu, tau) and L-+/- -> W(+/-)v (v = v(e), v(mu), v(tau)) are considered. The analysis is performed using the final state that contains two leptons (electrons or muons), two jets from a hadronically decaying W boson and large missing transverse momentum. The data used in the measurement correspond to an integrated luminosity of 20.3 fb(-1) of pp collisions at root s = 8 TeV collected by the ATLAS detector at the LHC. No evidence of heavy lepton pair production is observed. H…

Combination of CDF and D0 measurements of the W boson helicity in top quark decays

2012

Aaltonen, T. et al.

Net-charge fluctuations in Pb-Pb collisions at sqrt[sNN]=2.76TeV.

2013

We report the first measurement of the net-charge fluctuations in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV, measured with the ALICE detector at the CERN Large Hadron Collider. The dynamical fluctuations per unit entropy are observed to decrease when going from peripheral to central collisions. An additional reduction in the amount of fluctuations is seen in comparison to the results from lower energies. We examine the dependence of fluctuations on the pseudo-rapidity interval, which may account for the dilution of fluctuations during the evolution of the system. We find that the ALICE data points are between the theoretically predicted values for a hadron gas and a Quark-Gluon Plasma.…

Search for neutral MSSM Higgs bosons decaying to τ+τ− pairs in proton–proton collisions at s=7 TeV with the ATLAS detector

2011

A search for neutral Higgs bosons decaying to pairs of tau leptons with the ATLAS detector at the LHC is presented. The analysis is based on proton-proton collisions at a center-of-mass energy of 7 TeV, recorded in 2010 and corresponding to an integrated luminosity of 36 pb^-1. After signal selection, 276 events are observed in this data sample. The observed number of events is consistent with the total expected background of 269 +/- 36 events. Exclusion limits at the 95% confidence level are derived for the production cross section of a generic Higgs boson phi as a function of the Higgs boson mass and for A/H/h production in the Minimal Supersymmetric Standard Model (MSSM) as a function of…

Top quark mass measurement in the lepton plus jets channel using a modified matrix element method

2008

We report a measurement of the top quark mass, m(t), obtained from p(p)over bar collisions at root s=1.96 TeV at the Fermilab Tevatron using the CDF II detector. We analyze a sample corresponding to an integrated luminosity of 1.9 fb(-1). We select events with an electron or muon, large missing transverse energy, and exactly four high-energy jets in the central region of the detector, at least one of which is tagged as coming from a b quark. We calculate a signal likelihood using a matrix element integration method, where the matrix element is modified by using effective propagators to take into account assumptions on event kinematics. Our event likelihood is a function of m(t) and a parame…

Search for massive, long-lived particles using multitrack displaced vertices or displaced lepton pairs inppcollisions ats=8  TeVwith the ATLAS detect…

2015

Many extensions of the Standard Model posit the existence of heavy particles with long lifetimes. This article presents the results of a search for events containing at least one long-lived particle that decays at a significant distance from its production point into two leptons or into five or more charged particles. This analysis uses a data sample of proton-proton collisions at root s = 8 TeV corresponding to an integrated luminosity of 20.3 fb(-1) collected in 2012 by the ATLAS detector operating at the Large Hadron Collider. No events are observed in any of the signal regions, and limits are set on model parameters within supersymmetric scenarios involving R-parity violation, split sup…

Measurement of the inclusive isolated prompt photon cross section inppcollisions ats=7  TeVwith the ATLAS detector

2011

A measurement of the cross section for the inclusive production of isolated prompt photons in pp collisions at a center-of-mass energy root s = 7 TeV is presented. The measurement covers the pseudorapidity ranges vertical bar eta(gamma)vertical bar < 1: 37 and 1: 52 <= vertical bar eta(gamma)vertical bar < 1: 81 in the transverse energy range 15 <= E-T(gamma) < 100 GeV. The results are based on an integrated luminosity of 880 nb(-1), collected with the ATLAS detector at the Large Hadron Collider. Photon candidates are identified by combining information from the calorimeters and from the inner tracker. Residual background in the selected sample is estimated from data based on the observed d…

Measurements of branching fraction ratios andCPasymmetries inB±→DCPK±decays in hadron collisions

2010

9 paginas, 3 figuras, 2 tablas.-- PACS numbers: 13.25.Hw, 11.30.Er, 14.40.Nd.--CDF Collaboration: et al.

Anisotropic flow of charged hadrons, pions and (anti-)protons measured at high transverse momentum in Pb–Pb collisions at sNN=2.76 TeV

2013

The elliptic, v(2), triangular, v(3), and quadrangular, v(4), azimuthal anisotropic flow coefficients are measured for unidentified charged particles, pions, and (anti-)protons in Pb-Pb collisions at root S-NN = 2.76 TeV with the ALICE detector at the Large Hadron Collider. Results obtained with the event plane and four-particle cumulant methods are reported for the pseudo-rapidity range vertical bar eta vertical bar 8 GeV/c. The small p(T) dependence of the difference between elliptic flow results obtained from the event plane and four-particle cumulant methods suggests a common origin of flow fluctuations up to p(T) = 8 GeV/c. The magnitude of the (anti-)proton elliptic and triangular flo…

Search for excited leptons in proton-proton collisions ats=7  TeVwith the ATLAS detector

2012

The ATLAS detector is used to search for excited leptons in the electromagnetic radiative decay channel l* -> l gamma. Results are presented based on the analysis of pp collisions at a center-of ...

Search for a Charged Higgs Boson Produced in the Vector-Boson Fusion Mode with DecayH±→W±ZusingppCollisions ats=8  TeVwith the ATLAS Experiment

2015

A search for a charged Higgs boson, H-+/-, decaying to a W-+/- boson and a Z boson is presented. The search is based on 20.3 fb(-1) of proton-proton collision data at a center-of-mass energy of 8 TeV recorded with the ATLAS detector at the LHC. The H-+/- boson is assumed to be produced via vector-boson fusion and the decays W-+/- -> q (q') over bar and Z -> e(+)e(-)/mu(+)mu(-) are considered. The search is performed in a range of charged Higgs boson masses from 200 to 1000 GeV. No evidence for the production of an H+ boson is observed. Upper limits of 31-1020 fb at 95% C.L. are placed on the cross section for vector-boson fusion production of an H-+/- boson times its branching fraction to W…

Two-pion Bose-Einstein correlations inppcollisions ats=900  GeV

2010

We report on the measurement of two-pion correlation functions from pp collisions at root s = 900 GeV performed by the ALICE experiment at the Large Hadron Collider. Our analysis shows an increase of the Hanbury Brown-Twiss radius with increasing event multiplicity, in line with other measurements done in particle- and nuclear collisions. Conversely, the strong decrease of the radius with increasing transverse momentum, as observed at the Relativistic Heavy Ion Collider and at Tevatron, is not manifest in our data.

Measurement of t ¯ t production with a veto on additional central jet activity in pp collisions at √ s = 7 TeV using the ATLAS detector

2012

A measurement of the jet activity in t[bar over t] events produced in proton–proton collisions at a centre-of-mass energy of 7 TeV is presented, using 2.05 fb[superscript −1] of integrated luminosity collected by the ATLAS detector at the Large Hadron Collider. The t[bar over t] events are selected in the dilepton decay channel with two identified b-jets from the top quark decays. Events are vetoed if they contain an additional jet with transverse momentum above a threshold in a central rapidity interval. The fraction of events surviving the jet veto is presented as a function of this threshold for four different central rapidity interval definitions. An alternate measurement is also perfor…

Tevatron constraints on models of the Higgs boson with exotic spin and parity using decays to bottom-antibottom quark pairs.

2015

et al.

Measurement of the b-hadron production cross section using decays to D⁎+μ−X final states in pp collisions at s=7 TeV with the ATLAS detector

2012

The b-hadron production cross section is measured with the ATLAS detector in pp collisions at root s = 7 TeV, using 3.3 pb(-1) of integrated luminosity, collected during the 2010 LHC run. The b-had ...

Search for photonic signatures of gauge-mediated supersymmetry in 8TeV pp collisions with the ATLAS detector

2015

A search is presented for photonic signatures motivated by generalized models of gauge-mediated supersymmetry breaking. This search makes use of 20.3  fb[superscript −1] of proton-proton collision data at √s = 8  TeV recorded by the ATLAS detector at the LHC, and explores models dominated by both strong and electroweak production of supersymmetric partner states. Four experimental signatures incorporating an isolated photon and significant missing transverse momentum are explored. These signatures include events with an additional photon, lepton, b-quark jet, or jet activity not associated with any specific underlying quark flavor. No significant excess of events is observed above the Stand…

J-PARC E07: Systematic Study of Double Strangeness System with Hybrid Emulsion Method

2021

Measurement of theΛb0Lifetime inΛb0→Λc+π−Decays inpp¯Collisions ats=1.96  TeV

2007

We thank the Fermilab staff and the technical staffs of the participating institutions for their vital contributions. This work was supported by the U.S. Department of Energy and National Science Foundation; the Italian Istituto Nazionale di Fisica Nucleare; the Ministry of Education, Culture, Sports, Science and Technology of Japan; the Natural Sciences and Engineering Research Council of Canada; the National Science Council of the Republic of China; the Swiss National Science Foundation; the A.P. Sloan Foundation; the Bundesministerium fur Bildung und Forschung, Germany; the World Class University Program, the National Research Foundation of Korea; the Science and Technology Facilities Co…

Surgeons' fear of getting infected by COVID19: A global survey

2020

During the last three months, COVID- 19 pandemic had led to a serious backlog of operations globally, and plans for restarting operation are imperative. Recommendations for surgical activities were studied, aiming to protect the surgical staff from being infected. In the meantime, it is also important to give attention to the surgeon’s personal feeling during work. We conducted a survey to investigate global surgi- cal practices during the COVID-19 pandemic, and the surgeon’s personal feeling was also investigated in the sur- vey. In this special letter, we performed multivariate analysis to explore factors that associated with surgeon’s fear of getting infected by COVID-19.

Search for the Production of Scalar Bottom Quarks inpp¯Collisions ats=1.96  TeV

2010

We report on a search for direct scalar bottom quark (sbottom) pair production in pp collisions at {radical}(s)=1.96 TeV, in events with large missing transverse energy and two jets of hadrons in the final state, where at least one of the jets is required to be identified as originating from a b quark. The study uses a collider detector at Fermilab Run II data sample corresponding to 2.65 fb{sup -1} of integrated luminosity. The data are in agreement with the standard model. In an R-parity conserving minimal supersymmetric scenario, and assuming that the sbottom decays exclusively into a bottom quark and a neutralino, 95% confidence-level upper limits on the sbottom pair production cross se…

Search for nonpointing photons in the diphoton andETmissfinal state ins=7  TeVproton-proton collisions using the ATLAS detector

2013

A search has been performed for photons originating in the decay of a neutral long-lived particle, exploiting the capabilities of the ATLAS electromagnetic calorimeter to make precise measurements of the flight direction of photons, as well as the calorimeter's excellent time resolution. The search has been made in the diphoton plus missing transverse energy final state, using the full data sample of 4.8 fb(-1) of 7 TeV proton-proton collisions collected in 2011 with the ATLAS detector at the LHC. No excess is observed above the background expected from Standard Model processes. The results are used to set exclusion limits in the context of gauge mediated supersymmetry breaking models, with…

Observation and Mass Measurement of the BaryonΞb−

2007

We report the observation and measurement of the mass of the bottom, strange baryon $\Xi^-_b$ through the decay chain $\Xi^-_b \to J/\psi \Xi^-$, where $J/\psi \to \mu^+ \mu^-$, $\Xi^- \to \Lambda \pi^-$, and $\Lambda \to p \pi^-$. Evidence for observation is based on a signal whose probability of arising from the estimated background is 6.6 x 10^{-15}, or 7.7 Gaussian standard deviations. The $\Xi^-_b$ mass is measured to be $5792.9\pm 2.5$ (stat.) $\pm 1.7$ (syst.) MeV/$c^2$.

Search for strong gravity signatures in same-sign dimuon final states using the ATLAS detector at the LHC

2012

A search for microscopic black holes has been performed in a same-sign dimuon final state using 1.3 fb[superscript −1] of proton–proton collision data collected with the ATLAS detector at a centre of mass energy of 7 TeV at the CERN Large Hadron Collider. The data are found to be consistent with the expectation from the Standard Model and the results are used to derive exclusion contours in the context of a low scale gravity model.

Measurements of the Nuclear Modification Factor for Jets inPb+PbCollisions atsNN=2.76  TeVwith the ATLAS Detector

2015

Measurements of inclusive jet production are performed in pp and Pb+Pb collisions at √sNN = 2.76 TeV with the ATLAS detector at the LHC, corresponding to integrated luminosities of 4.0 pb−1 and 0.14 nb−1, respectively. The jets are identified with the anti-kt algorithm with R = 0.4, and the spectra are measured over the kinematic range of jet transverse momentum 32 < pT < 500 GeV, and absolute rapidity |y| < 2.1 and as a function of collision centrality. The nuclear modification factor, RAA, is evaluated and jets are found to be suppressed by approximately a factor of two in central collisions compared to pp collisions. The RAA shows a slight increase with pT and no significant variation wi…

Measurements of normalized differential cross sections fortt¯production inppcollisions at(s)=7  TeVusing the ATLAS detector

2014

Measurements of normalized differential cross sections for top-quark pair production are presented as a function of the top-quark transverse momentum, and of the mass, transverse momentum, and rapidity of the t (t) over bar system, in proton proton collisions at a center-of-mass energy of root s = 7 TeV. The data set corresponds to an integrated luminosity of 4.6 fb(-1), recorded in 2011 with the ATLAS detector at the CERN Large Hadron Collider. Events are selected in the lepton jets channel, requiring exactly one lepton and at least four jets with at least one of the jets tagged as originating from a b-quark. The measured spectra are corrected for detector efficiency and resolution effects…

Search for Magnetic Monopoles ins=7  TeVppCollisions with the ATLAS Detector

2012

This Letter presents a search for magnetic monopoles with the ATLAS detector at the CERN Large Hadron Collider using an integrated luminosity of 2.0 fb(-1) of pp collisions recorded at a center-of- ...

Search for Gluinos in Events with Two Same-Sign Leptons, Jets, and Missing Transverse Momentum with the ATLAS Detector in Collisions at

2012

A search is presented for gluinos decaying via the supersymmetric partner of the top quark using events with two same-sign leptons, jets, and missing transverse momentum. The analysis is performed ...

Search for third generation vector leptoquarks inpp¯collisions ats=1.96  TeV

2008

We search for a third generation vector leptoquark (VLQ3) that decays to a b quark and tau lepton using the CDF II detector and 320pb-1 of integrated luminosity from the Fermilab Tevatron. Observing a number of events in agreement with standard model expectations, we obtain, assuming Yang-Mills (minimal) couplings, the most stringent upper limit on the VLQ3 pair production cross section of 344 fb (493 fb) and lower limit on the VLQ3 mass of 317GeV/c2 (251GeV/c2) at 95% C.L. © 2008 The American Physical Society.

Ds+ meson production at central rapidity in proton–proton collisions at s=7 TeV

2012

The pt-differential inclusive production cross section of the prompt charm-strange meson D_s in the rapidity range |y| phi pi, with phi -> KK, and its charge conjugate, about 480 D_s mesons were counted, after selection cuts, in the transverse momentum range 2

Charged-Particle Multiplicity Density at Midrapidity in Central Pb-Pb Collisions atsNN=2.76  TeV

2010

The first measurement of the charged-particle multiplicity density at midrapidity in Pb-Pb collisions at a center-of-mass energy per nucleon pair root s(NN) = 2.76 TeV is presented. For an event sample corresponding to the most central 5% of the hadronic cross section, the pseudorapidity density of primary charged particles at midrapidity is 1584 +/- 4(stat) +/- 76(syst), which corresponds to 8.3 +/- 0.4(syst) per participating nucleon pair. This represents an increase of about a factor 1.9 relative to pp collisions at similar collision energies, and about a factor 2.2 to central Au-Au collisions at root s(NN) = 0.2 TeV. This measurement provides the first experimental constraint for models…

Search for the Production of Narrowtb¯Resonances in1.9  fb−1ofpp¯Collisions ats=1.96  TeV

2009

We present new limits on resonant tb production in ppbar collisions at sqrt(s) = 1.96 TeV, using 1.9 fb{sup -1} of data recorded with the CDF II detector at the Fermilab Tevatron. We reconstruct a putative tb mass in events with a lepton, neutrino candidate, and two or three jets, and search for anomalous tb production as modeled by W{prime} {yields} tb. We set a new limit on a right-handed W{prime} with standard model-like coupling, excluding any mass below 800 GeV at 95% C.L. For any narrow W{prime}-like state with mass above 800 GeV, the cross-section is found to be less than 0.28 pb at 95% C.L. We also present an exclusion of the W{prime} coupling strength versus W{prime} mass.

Underlying event characteristics and their dependence on jet size of charged-particle jet events inppcollisions at(s)=7  TeVwith the ATLAS detector

2012

Distributions sensitive to the underlying event are studied in events containing one or more charged-particle jets produced in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector at the Large Hadron Collider (LHC). These measurements reflect 800 inverse microbarns of data taken during 2010. Jets are reconstructed using the antikt algorithm with radius parameter R varying between 0.2 and 1.0. Distributions of the charged-particle multiplicity, the scalar sum of the transverse momentum of charged particles, and the average charged-particle pT are measured as functions of pT^JET in regions transverse to and opposite the leading jet for 4 GeV < pT^JET < 100 GeV. In addition, the R-dependen…

Measurement ofW-Boson Polarization in Top-Quark Decay inpp¯Collisions ats=1.96  TeV

2010

We report measurements of the polarization of W bosons from top-quark decays using 2.7 fb(-1) of p (p) over bar collisions collected by the CDF II detector. Assuming a top-quark mass of 175 GeV/c(2), three measurements are performed. A simultaneous measurement of the fraction of longitudinal (f(0)) and right-handed (f(0)) W bosons yields the model- independent results f(0) =0. 88 +/- 0.11(stat) +/- 0.06(syst) and f(+) = 0.15 +/- 0.07(stat) +/- 0.06(syst) with a correlation coefficient of -0.59. A measurement of f(0) [f(+)] constraining f(+) [f(0)] to its standard model value of 0.0 [0.7] yields f(0) 0.70 + 0.07(stat) +/- 0.04(syst) [f(+) - 0.01 +/- 0.02(stat) +/- 0.05(syst)]. All these resu…

Measurement of the ϒ(1S) production cross-section in pp collisions at s=7 TeV in ATLAS

2011

A measurement of the cross-section for ϒ ( 1 S ) → μ + μ − production in proton–proton collisions at centre of mass energy of 7 TeV is presented. The cross-section is measured as a function of the ϒ ( 1 S ) transverse momentum in two bins of rapidity, | y ϒ ( 1 S ) | 4 GeV and pseudorapidity | η μ | < 2.5 in order to reduce theoretical uncertainties on the acceptance, which depend on the poorly known polarisation. The results are based on an integrated luminosity of 1.13 pb−1, collected with the ATLAS detector at the Large Hadron Collider. The cross-section measurement is compared to theoretical predictions: it agrees to within a factor of two with a prediction based on the NRQCD model incl…

Inclusive Search for Standard Model Higgs Boson Production in the WW Decay Channel using the CDF II Detector

2010

We present a search for standard model (SM) Higgs boson production using p (p) over bar collision data at root s = 1. 96 TeV, collected with the CDF II detector and corresponding to an integrated luminosity of 4. 8 fb(-1). We search for Higgs bosons produced in all processes with a significant production rate and decaying to two W bosons. We find no evidence for SM Higgs boson production and place upper limits at the 95% confidence level on the SM production cross section (sigma(H)) for values of the Higgs boson mass (m(H)) in the range from 110 to 200 GeV. These limits are the most stringent for m(H) > 130 GeV and are 1.29 above the predicted value of sigma(H) for m(H) 165 GeV.

Search for the neutral current top quark decayt→Zcusing the ratio ofZ-boson+4  jetstoW-boson+4  jetsproduction

2009

We have used the Collider Detector at Fermilab (CDF II) to search for the flavor-changing neutral-current (FCNC) top quark decay t {yields} Zc using a technique employing ratios of W and Z production, measured in p{bar p} data corresponding to an integrated luminosity of 1.52 fb{sup -1}. The analysis uses a comparison of two decay chains, p{bar p} {yields} t{bar t} {yields} WbWb {yields} {ell}{nu}bjjb and p{bar p} {yields} t{bar t} {yields} ZcWb {yields} {ell}{ell}cjjb, to cancel systematic uncertainties in acceptance, efficiency, and luminosity. We validate the modeling of acceptance and efficiency for lepton identification over the multi-year dataset using another ratio of W and Z product…

Determination of the Strange-Quark Density of the Proton from ATLAS Measurements of theW→ℓνandZ→ℓℓCross Sections

2012

AQCD analysis is reported of ATLAS data on inclusive W-+/- and Z boson production in pp collisions at the LHC, jointly with ep deep-inelastic scattering data from HERA. The ATLAS data exhibit sensitivity to the light quark sea composition and magnitude at Bjorken x similar to 0:01. Specifically, the data support the hypothesis of a symmetric composition of the light quark sea at low x. The ratio of the strange-to-down sea quark distributions is determined to be 1:00(-0:28)(+0.25) at absolute four-momentum transfer squared Q(2) = 1: 9 GeV2 and x = 0: 023.

Search for Supersymmetry in Events with Three Leptons and Missing Transverse Momentum ins=7  TeVppCollisions with the ATLAS Detector

2012

A search for the weak production of charginos and neutralinos decaying to a final state with three leptons (electrons or muons) and missing transverse momentum is presented. The analysis uses 2.06 fb(-1) of root s = 7 TeV proton-proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with standard model expectations in two signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric and simplified models. For the simplified models, degenerate lightest chargino and next-to-lightest neutralino masses up to …

Male and female fertility preservation

2013

Search for scalar top quark pair production in natural gauge mediated supersymmetry models with the ATLAS detector in pp collisions at s=7 TeV

2012

The results of a search for pair production of the lighter scalar partners of top quarks () in 2.05 fb−1 of pp collisions at TeV using the ATLAS experiment at the LHC are reported. Scalar top quar ...

Search for a Supersymmetric Partner to the Top Quark in Final States with Jets and Missing Transverse Momentum ats=7  TeVwith the ATLAS Detector

2012

A search for direct pair production of supersymmetric top squarks ((t) over tilde (1)) is presented, assuming the (t) over tilde (1) decays into a top quark and the lightest supersymmetric particle, (chi) over tilde (0)(1), and that both top quarks decay to purely hadronic final states. A total of 16 (4) events are observed compared to a predicted standard model background of 13.5(-3.6)(+3.7) (4.4(-1.3)(+1.7)) events in two signal regions based on integral Ldt = 4.7 fb(-1) of pp collision data taken at root s = 7 TeV with the ATLAS detector at the LHC. An exclusion region in the (t) over tilde (1) versus (chi) over tilde (0)(1) mass plane is evaluated: 370 1) 10) similar to 0 GeV while m((t…

Measurement of the production cross section of jets in association with a Z boson in pp collisions at $\sqrt{s}$ = 7 TeV with the ATLAS detector

2013

Measurements of the production of jets of particles in association with a Z boson in pp collisions at s√ = 7 TeV are presented, using data corresponding to an integrated luminosity of 4.6 fb[superscript −1] collected by the ATLAS experiment at the Large Hadron Collider. Inclusive and differential jet cross sections in Z events, with Z decaying into electron or muon pairs, are measured for jets with transverse momentum p [subscript T] > 30 GeV and rapidity |y| < 4.4. The results are compared to next-to-leading-order perturbative QCD calculations, and to predictions from different Monte Carlo generators based on leading-order and next-to-leading-order matrix elements supplemented by parton sh…

ATLAS measurements of the properties of jets for boosted particle searches

2012

Measurements are presented of the properties of high transverse momentum jets, produced in proton-proton collisions at a center-of-mass energy of √s=7  TeV. The data correspond to an integrated luminosity of 35  pb−1 and were collected with the ATLAS detector in 2010. Jet mass, width, eccentricity, planar flow and angularity are measured for jets reconstructed using the anti-kt algorithm with distance parameters R=0.6 and 1.0, with transverse momentum pT>300  GeV and pseudorapidity |η|<2. The measurements are compared to the expectations of Monte Carlo generators that match leading-logarithmic parton showers to leading-order, or next-to-leading-order, matrix elements. The generators describ…

Search for a heavy neutral particle decaying into an electron and a muon using 1 fb−1 of ATLAS data

2011

A search is presented for a high mass neutral particle that decays directly to the e±μ∓ final state. The data sample was recorded by the ATLAS detector in s√=7~TeVpp collisions at the LHC from March to June 2011 and corresponds to an integrated luminosity of 1.07 fb−1. The data are found to be consistent with the Standard Model background. The high e±μ∓ mass region is used to set 95% confidence level upper limits on the production of two possible new physics processes: tau sneutrinos in an R-parity violating supersymmetric model and Z′-like vector bosons in a lepton flavor violating model.

Search for standard model Higgs bosons produced in association with W bosons.

2007

We report on the results of a search for standard model Higgs bosons produced in association with W bosons from p-pbar collisions at root s = 1.96 TeV. The search uses a data sample corresponding to approximately 1 fb-1 of integrated luminosity. Events consistent with the W to l-nu and H to b-bbar signature are selected by triggering on a high-pT electron or muon candidate and tagging one or two of the jet candidates as having originated from b quarks. A neural network filter rejects a fraction of tagged charm and light flavor jets, increasing the b-jet purity in the sample and thereby reducing the background to Higgs boson production. We observe no excess l-nu-b-bbar production beyond the …

Observation of a NewχbState in Radiative Transitions toΥ(1S)andΥ(2S)at ATLAS

2012

The χb(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider at √s=7  TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4  fb-1, these states are reconstructed through their radiative decays to Υ(1S,2S) with Υ→μ+μ-. In addition to the mass peaks corresponding to the decay modes χb(1P,2P)→Υ(1S)γ, a new structure centered at a mass of 10.530±0.005(stat)±0.009(syst)  GeV is also observed, in both the Υ(1S)γ and Υ(2S)γ decay modes. This structure is interpreted as the χb(3P) system.

Midrapidity Antiproton-to-Proton Ratio inppCollisons ats=0.9and 7 TeV Measured by the ALICE Experiment

2010

The ratio of the yields of antiprotons to protons in pp collisions has been measured by the ALICE experiment at root s = 0.9 and 7 TeV during the initial running periods of the Large Hadron Collider. The measurement covers the transverse momentum interval 0.45 < p(t) < 1.05 GeV/c and rapidity vertical bar y vertical bar < 0.5. The ratio is measured to be R-vertical bar y vertical bar<0.5 = 0.957 +/- 0.006(stat) +/- 0.0014(syst) at 0.9 Tev and R-vertical bar y vertical bar<0.5 = 0.991 +/- 0.005 +/- 0.014(syst) at 7 TeV and it is independent of both rapidity and transverse momentum. The results are consistent with the conventional model of baryon-number transport and set stringent limits on a…

Elliptic Flow of Charged Particles in Pb-Pb Collisions atsNN=2.76  TeV

2010

We report the first measurement of charged particle elliptic flow in Pb-Pb collisions at root s(NN) p = 2.76 TeV with the ALICE detector at the CERN Large Hadron Collider. The measurement is performed in the central pseudorapidity region (vertical bar eta vertical bar < 0.8) and transverse momentum range 0.2 < p(t) < 5.0 GeV/c. The elliptic flow signal v(2), measured using the 4-particle correlation method, averaged over transverse momentum and pseudorapidity is 0.087 +/- 0.002(stat) +/- 0.003(syst) in the 40%-50% centrality class. The differential elliptic flow v(2)(p(t)) reaches a maximum of 0.2 near p(t) = 3 GeV/c. Compared to RHIC Au-Au collisions at root s(NN) = 200 GeV, the elliptic f…

OUP accepted manuscript

2021

Measurement of the single-top-quark production cross section at CDF.

2008

We report a measurement of the single top quark production cross section in 2.2 ~fb-1 of p-pbar collision data collected by the Collider Detector at Fermilab at sqrt{s}=1.96 TeV. Candidate events are classified as signal-like by three parallel analyses which use likelihood, matrix element, and neural network discriminants. These results are combined in order to improve the sensitivity. We observe a signal consistent with the standard model prediction, but inconsistent with the background-only model by 3.7 standard deviations with a median expected sensitivity of 4.9 standard deviations. We measure a cross section of 2.2 +0.7 -0.6(stat+sys) pb, extract the CKM matrix element value |V_{tb}|=0…

Multi-channel search for squarks and gluinos in root s=7 TeV pp collisions with the ATLAS detector at the LHC

2013

A search for supersymmetric particles in final states with zero, one, and two leptons, with and without jets identified as originating from b-quarks, in 4.7 fb[superscript −1] of √s = 7 TeV pp collisions produced by the Large Hadron Collider and recorded by the ATLAS detector is presented. The search uses a set of variables carrying information on the event kinematics transverse and parallel to the beam line that are sensitive to several topologies expected in supersymmetry. Mutually exclusive final states are defined, allowing a combination of all channels to increase the search sensitivity. No deviation from the Standard Model expectation is observed. Upper limits at 95 % confidence level…

Measurement of the top quark charge in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector

2013

A measurement of the top quark electric charge is carried out in the ATLAS experiment at the Large Hadron Collider using 2.05 fb[superscript −1] of data at a centre-of-mass energy of 7 TeV. In units of the elementary electric charge, the top quark charge is determined to be 0.64 ± 0.02 (stat.) ± 0.08 (syst.) from the charges of the top quark decay products in single lepton t[¯ over t] candidate events. This excludes models that propose a heavy quark of electric charge −4/3, instead of the Standard Model top quark, with a significance of more than 8σ.

Search for new particles decaying to ZZ using final states with leptons and jets with the ATLAS detector in s=7 TeV proton–proton collisions

2012

A search is presented for a narrow resonance decaying to a pair of Z bosons using data corresponding to 1.02 fb(-1) of integrated luminosity collected by the ATLAS experiment from pp collisions at ...

Search for invisible Higgs boson decays in vector boson fusion at s=13TeV with the ATLAS detector

2019

We report a search for Higgs bosons that are produced via vector boson fusion and subsequently decay into invisible particles. The experimental signature is an energetic jet pair with invariant mass of O(1)TeV and O(100)GeV missing transverse momentum. The analysis uses 36.1 fb −1 of pp collision data at s=13TeV recorded by the ATLAS detector at the LHC. In the signal region the 2252 observed events are consistent with the background estimation. Assuming a 125GeV scalar particle with Standard Model cross sections, the upper limit on the branching fraction of the Higgs boson decay into invisible particles is 0.37 at 95% confidence level where 0.28 was expected. This limit is interpreted in H…

Measurement of the tt¯ production cross section in the τ+jets final state in pp collisions at s=8  TeV using the ATLAS detector

2017

A measurement of the inclusive pp -> t (t) over bar + X production cross section in the tau + jets final state using only the hadronic decays of the tau lepton is presented. The measurement is p ...

Hunt for new phenomena using large jet multiplicities and missing transverse momentum with ATLAS in 4.7 fb[superscript −1] of √s = 7 TeV proton-proto…

2012

Results are presented of a search for new particles decaying to large numbers of jets in association with missing transverse momentum, using 4.7 fb[superscript −1] of pp collision data at √s = 7 TeV collected by the ATLAS experiment at the Large Hadron Collider in 2011. The event selection requires missing transverse momentum, no isolated electrons or muons, and from ≥6 to ≥9 jets. No evidence is found for physics beyond the Standard Model. The results are interpreted in the context of a MSUGRA/CMSSM supersymmetric model, where, for large universal scalar mass m [subscript 0], gluino masses smaller than 840 GeV are excluded at the 95% confidence level, extending previously published limits.…

Measurement of inclusive jet and dijet cross sections in proton-proton collisions at 7 TeV centre-of-mass energy with the ATLAS detector

2011

Jet cross sections have been measured for the first time in proton-proton collisions at a centre-of-mass energy of 7 TeV using the ATLAS detector. The measurement uses an integrated luminosity of 17 nb−1 recorded at the Large Hadron Collider. The anti-k t algorithm is used to identify jets, with two jet resolution parameters, R=0.4 and 0.6. The dominant uncertainty comes from the jet energy scale, which is determined to within 7% for central jets above 60 GeV transverse momentum. Inclusive single-jet differential cross sections are presented as functions of jet transverse momentum and rapidity. Dijet cross sections are presented as functions of dijet mass and the angular variable χ. The res…

Measurement ofD*±meson production in jets fromppcollisions ats=7  TeVwith the ATLAS detector

2012

This paper reports a measurement of D*(+/-) meson production in jets from proton- proton collisions at a center- of- mass energy of root s = 7 TeV at the CERN Large Hadron Collider. The measurement is based on a data sample recorded with the ATLAS detector with an integrated luminosity of 0.30 pb(-1) for jets with transverse momentum between 25 and 70 GeV in the pseudorapidity range vertical bar eta vertical bar D-0 pi(+), D-0 -> K-pi(+), and its charge conjugate. The production rate is found to be N(D*(+/-))/N(jet) = 0.025 +/- 0.001(stat.) +/- 0.004(syst.) for D*(+/-) mesons that carry a fraction z of the jet momentum in the range 0.3< z< 1. Monte Carlo predictions fail to describe the dat…

Search for high-mass resonances decaying to dilepton final states in pp collisions at √s = 7 TeV with the ATLAS detector

2012

The ATLAS detector at the Large Hadron Collider is used to search for high-mass resonances decaying to an electron-positron pair or a muon-antimuon pair. The search is sensitive to heavy neutral Z′ gauge bosons, Randall-Sundrum gravitons, Z [superscript *] bosons, techni-mesons, Kaluza-Klein Z/γ bosons, and bosons predicted by Torsion models. Results are presented based on an analysis of pp collisions at a center-of-mass energy of 7 TeV corresponding to an integrated luminosity of 4.9 fb[superscript −1] in the e [superscript +] e [superscript −] channel and 5.0 fb[superscript −1] in the μ [superscript +] μ [superscript −] channel. A Z [superscript ′] boson with Standard Model-like couplings…

Measurement of the Ratioσtt¯/σZ/γ*→lland Precise Extraction of thett¯Cross Section

2010

We report a measurement of the ratio of the t (t) over bar to Z/gamma* production cross sections in root s = 1.96 TeV p (p) over bar collisions using data corresponding to an integrated luminosity of up to 4.6 fb(-1), collected by the CDF II detector. The t (t) over bar cross section ratio is measured using two complementary methods, a b-jet tagging measurement and a topological approach. By multiplying the ratios by the well-known theoretical Z/gamma* -> ll cross section predicted by the standard model, the extracted t (t) over bar cross sections are effectively insensitive to the uncertainty on luminosity. A best linear unbiased estimate is used to combine both measurements with the resul…

Cross section measurements of high-p(T) dilepton final-state processes using a global fitting method

2008

We present a new method for studying high-$p_T$ dilepton events ($e^{\pm}e^{\mp}$, $\mu^{\pm}\mu^{\mp}$, $e^{\pm}\mu^{\mp}$) and simultaneously extracting the production cross sections of $p\bar{p} \to t\bar{t}$, $p\bar{p} \to W^+W^-$, and $p\bar{p} \to \ztt$ at a center-of-mass energy of $\sqrt{s} = 1.96$ TeV. We perform a likelihood fit to the dilepton data in a parameter space defined by the missing transverse energy and the number of jets in the event. Our results, which use $360 {\rm pb^{-1}}$ of data recorded with the CDF II detector at the Fermilab Tevatron Collider, are $\sigma(t\bar{t}) = 8.5_{-2.2}^{+2.7}$ pb, $\sigma(W^+W^-) = 16.3^{+5.2}_{-4.4}$ pb, and $\sigma(\ztt) =291^{+50}_…

Neutron emission from electromagnetic dissociation of Pb nuclei at $\sqrt {s_{NN}} = 2.76$ TeV measured with the ALICE ZDC

2014

The ALICE Zero Degree Calorimeter system (ZDC) is composed of two identical sets of calorimeters, placed at opposite sides with respect to the interaction point, 114 meters away from it, complemented by two small forward electromagnetic calorimeters (ZEM). Each set of detectors consists of a neutron (ZN) and a proton (ZP) ZDC. They are placed at zero degrees with respect to the LHC axis and allow to detect particles emitted close to beam direction, in particular neutrons and protons emerging from hadronic heavy-ion collisions (spectator nucleons) and those emitted from electromagnetic processes. For neutrons emitted by these two processes, the ZN calorimeters have nearly 100% acceptance. Du…

Search for Supersymmetry inppCollisions ats=7  TeVin Events with Two Photons and Missing Transverse Energy

2011

A search for supersymmetry in the context of general gauge-mediated breaking with the lightest neutralino as the next-to-lightest supersymmetric particle and the gravitino as the lightest is presented. The data sample corresponds to an integrated luminosity of 36 pb(-1) recorded by the CMS experiment at the LHC. The search is performed by using events containing two or more isolated photons, at least one hadronic jet, and significant missing transverse energy. No excess of events at high missing transverse energy is observed. Upper limits on the signal cross section for general gauge-mediated supersymmetry between 0.3 and 1.1 pb at the 95% confidence level are determined for a range of squa…

Measurement of the top quark mass andpp¯→tt¯cross section in the all-hadronic mode with the CDF II detector

2010

We present a measurement of the top quark mass and of the top-antitop pair production cross section using p-pbar data collected with the CDFII detector at the Tevatron Collider at the Fermi National Accelerator Laboratory and corresponding to an integrated luminosity of 2.9 fb-1. We select events with six or more jets satisfying a number of kinematical requirements imposed by means of a neural network algorithm. At least one of these jets must originate from a b quark, as identified by the reconstruction of a secondary vertex inside the jet. The mass measurement is based on a likelihood fit incorporating reconstructed mass distributions representative of signal and background, where the abs…

Search for anomalous production of prompt like-sign muon pairs and constraints on physics beyond the Standard Model with the ATLAS detector

2012

An inclusive search for anomalous production of two prompt, isolated muons with the same electric charge is presented. The search is performed in a data sample corresponding to 1.6  fb−1 of integrated luminosity collected in 2011 at √s=7  TeV with the ATLAS detector at the LHC. Muon pairs are selected by requiring two isolated muons of the same electric charge with pT>20  GeV and |η|<2.5. Minimal requirements are placed on the rest of the event activity. The distribution of the invariant mass of the muon pair m(μμ) is found to agree well with the background expectation. Upper limits on the cross section for anomalous production of two muons with the same electric charge are placed as a func…

Measurement of the top pair production cross section in the dilepton decay channel inpp¯collisions ats=1.96  TeV

2010

A measurement of the tt production cross section in pp collisions at {radical}(s)=1.96 TeV using events with two leptons, missing transverse energy, and jets is reported. The data were collected with the CDF II detector. The result in a data sample corresponding to an integrated luminosity 2.8 fb{sup -1} is {sigma}{sub tt}=6.27{+-}0.73(stat){+-}0.63(syst){+-}0.39(lum) pb. for an assumed top mass of 175 GeV/c{sup 2}.