0000000000209276
AUTHOR
G. C. Grossi
Measurement of the Soft-Drop Jet Mass in pp Collisions at s=13 TeV with the ATLAS Detector
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 ...
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
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…
Measurement of the top pair production cross section in 8 TeV proton-proton collisions using kinematic information in thelepton+jetsfinal state with ATLAS
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…
Evidence ofWγγProduction inppCollisions ats=8 TeVand Limits on Anomalous Quartic Gauge Couplings with the ATLAS Detector
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.
Probing the Quantum Interference between Singly and Doubly Resonant Top-Quark Production in pp Collisions at s=13 TeV with the ATLAS Detector
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…
Measurements of four-lepton production in pp collisions at s=8 TeV with the ATLAS detector
A search is presented for a high-mass Higgs boson in the , , , and decay modes using the ATLAS detector at the CERN Large Hadron Collider. The search uses proton-proton collision data at a centre-o ...
Measurement of the cross section of high transverse momentumZ→bb¯production in proton–proton collisions ats=8 TeVwith the ATLAS detector
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…
The ATLAS Data Acquisition and High Level Trigger system
Journal of Instrumentation 11(06), P06008 (2016). doi:10.1088/1748-0221/11/06/P06008
Search for Dark Matter in Events with a Hadronically DecayingWorZBoson and Missing Transverse Momentum inppCollisions ats=8 TeVwith the ATLAS Detector
A search is presented for dark matter pair production in association with a W or Z boson in pp collisions representing 20.3 fb(-1) of integrated luminosity at root s = 8 TeV using data recorded with the ATLAS detector at the Large Hadron Collider. Events with a hadronic jet with the jet mass consistent with a W or Z boson, and with large missing transverse momentum are analyzed. The data are consistent with the standard model expectations. Limits are set on the mass scale in effective field theories that describe the interaction of dark matter and standard model particles, and on the cross section of Higgs production and decay to invisible particles. In addition, cross section limits on the…
Search for new phenomena in events with a photon and missing transverse momentum inppcollisions ats=8 TeVwith the ATLAS detector
© 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 a multi-Higgs-boson cascade inW+W−bb¯events with the ATLAS detector inppcollisions ats=8 TeV
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…
Constraints on off-shell Higgs boson production and the Higgs boson total width in ZZ → 4ℓ and ZZ → 2ℓ2ν final states with the ATLAS detector
A measurement of off-shell Higgs boson production in the and decay channels, where ℓ stands for either an electron or a muon, is performed using data from proton–proton collisions at a centre-of-mass energy of TeV. The data were collected by the ATLAS experiment in 2015 and 2016 at the Large Hadron Collider, and they correspond to an integrated luminosity of . An observed (expected) upper limit on the off-shell Higgs signal strength, defined as the event yield normalised to the Standard Model prediction, of 3.8 (3.4) is obtained at 95% confidence level (CL). Assuming the ratio of the Higgs boson couplings to the Standard Model predictions is independent of the momentum transfer of the Higgs…
Measurement of the transverse polarization ofΛandΛ¯hyperons produced in proton-proton collisions ats=7 TeVusing the ATLAS detector
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. …
Measurement of jet charge in dijet events froms=8 TeVppcollisions with the ATLAS detector
The momentum-weighted sum of the charges of tracks associated to a jet is sensitive to the charge of the initiating quark or gluon. This paper presents a measurement of the distribution of momentum ...
Search for Scalar Charm Quark Pair Production inppCollisions ats=8 TeVwith the ATLAS Detector
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 differential cross-section of highly boosted top quarks as a function of their transverse momentum ins=8 TeVproton-proton collisions using the ATLAS detector
The differential cross-section for pair production of top quarks with high transverse momentum is measured in 20.3 fb(-1) of proton-proton collisions at a center-of-mass energy of 8 TeV. The measur ...
A neural network clustering algorithm for the ATLAS silicon pixel detector
A novel technique to identify and split clusters created by multiple charged particles in the ATLAS pixel detector using a set of artificial neural networks is presented. Such merged clusters are a common feature of tracks originating from highly energetic objects, such as jets. Neural networks are trained using Monte Carlo samples produced with a detailed detector simulation. This technique replaces the former clustering approach based on a connected component analysis and charge interpolation. The performance of the neural network splitting technique is quantified using data from proton-proton collisions at the LHC collected by the ATLAS detector in 2011 and from Monte Carlo simulations. …
Search for Resonant and Nonresonant Higgs Boson Pair Production in the bb¯τ+τ− Decay Channel in pp Collisions at s=13 TeV with the ATLAS Detector
A search for resonant and nonresonant pair production of Higgs bosons in the b (b) over bar tau(+)tau(-) final state is presented. The search uses 36.1 fb(-1) of pp collision data with root s = 13 ...
Search for vectorlikeBquarks in events with one isolated lepton, missing transverse momentum, and jets ats=8 TeVwith the ATLAS detector
A search has been performed for pair production of heavy vectorlike down-type (B) quarks. The analysis explores the lepton-plus-jets final state, characterized by events with one isolated charged lepton (electron or muon), significant missing transverse momentum, and multiple jets. One or more jets are required to be tagged as arising from b quarks, and at least one pair of jets must be tagged as arising from the hadronic decay of an electroweak boson. The analysis uses the full data sample of pp collisions recorded in 2012 by the ATLAS detector at the LHC, operating at a center-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 20.3 fb(-1). No significant excess of event…
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 ATLAS detector
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 Higgs boson production in the diphoton decay channel inppcollisions at center-of-mass energies of 7 and 8 TeV with the ATLAS detector
A measurement of the production processes of the recently discovered Higgs boson is performed in the two-photon final state using 4.5 fb(-1) of proton-proton collisions data at root s = 7 TeV and 20.3 fb(-1) at root s = 8 TeV collected by the ATLAS detector at the Large Hadron Collider. The number of observed Higgs boson decays to diphotons divided by the corresponding Standard Model prediction, called the signal strength, is found to be mu = 1.17 +/- 0.27 at the value of the Higgs boson mass measured by ATLAS, m(H) = 125.4 GeV. The analysis is optimized to measure the signal strengths for individual Higgs boson production processes at this value of m(H). They are found to be mu(ggF) = 1.32…
Search for Higgs andZBoson Decays toJ/ψγandϒ(nS)γwith the ATLAS Detector
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.
Measurement of Spin Correlation in Top-Antitop Quark Events and Search for Top Squark Pair Production inppCollisions ats=8 TeVUsing the ATLAS Detector
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
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…
Measurements of spin correlation in top-antitop quark events from proton-proton collisions ats=7 TeVusing the ATLAS detector
Measurements of spin correlation in top quark pair production are presented using data collected with the ATLAS detector at the LHC with proton-proton collisions at a center-of-mass energy of 7 TeV, corresponding to an integrated luminosity of 4.6 fb(-1). Events are selected in final states with two charged leptons and at least two jets and in final states with one charged lepton and at least four jets. Four different observables sensitive to different properties of the top quark pair production mechanism are used to extract the correlation between the top and antitop quark spins. Some of these observables are measured for the first time. The measurements are in good agreement with the Stan…
Measurements of normalized differential cross sections fortt¯production inppcollisions at(s)=7 TeVusing the ATLAS detector
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 resonant WZ production in the fully leptonic final state in proton–proton collisions at s=13TeV with the ATLAS detector
A search for a heavy resonance decaying into WZ in the fully leptonic channel (electrons and muons) is performed. It is based on proton–proton collision data collected by the ATLAS experiment at the Large Hadron Collider at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 36.1 fb −1 . No significant excess is observed over the Standard Model predictions and limits are set on the production cross section times branching ratio of a heavy vector particle produced either in quark–antiquark fusion or through vector-boson fusion. Constraints are also obtained on the mass and couplings of a singly charged Higgs boson, in the Georgi–Machacek model, produced through ve…
Measurement of differentialJ/ψproduction cross sections and forward-backward ratios inp + Pbcollisions with the ATLAS detector
Measurements of differential cross sections for J/psi production in p + Pb collisions at root S-NN= 5.02 TeV at the CERN Large Hadron Collider with the ATLAS detector are presented. The data set us ...
Measurement of photon?jet transverse momentum correlations in 5.02 TeV Pb + Pb and pp collisions with ATLAS
Jets created in association with a photon can be used as a calibrated probe to study energy loss in the medium created in nuclear collisions. Measurements of the transverse momentum balance between isolated photons and inclusive jets are presented using integrated luminosities of 0.49 nb−1 of Pb + Pb collision data at TeV and 25 pb−1 of pp collision data at TeV recorded with the ATLAS detector at the LHC. Photons with transverse momentum GeV and are paired with all jets in the event that have GeV and pseudorapidity . The transverse momentum balance given by the jet-to-photon ratio, , is measured for pairs with azimuthal opening angle . Distributions of the per-photon jet yield as a function…
Monitoring and data quality assessment of the ATLAS liquid argon calorimeter
The liquid argon calorimeter is a key component of the ATLAS detector installed at the CERN Large Hadron Collider. The primary purpose of this calorimeter is the measurement of electron and photon kinematic properties. It also provides a crucial input for measuring jets and missing transverse momentum. An advanced data monitoring procedure was designed to quickly identify issues that would affect detector performance and ensure that only the best quality data are used for physics analysis. This article presents the validation procedure developed during the 2011 and 2012 LHC data-taking periods, in which more than 98% of the proton-proton luminosity recorded by ATLAS at a centre-of-mass ener…
Search for dark matter in events with heavy quarks and missing transverse momentum in [Formula: see text] collisions with the ATLAS detector.
This article reports on a search for dark matter pair production in association with bottom or top quarks in \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$20.3 \mathrm {~fb}^{-1}$$\end{document}20.3fb-1 of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$pp$$\end{document}pp collisions collected at \documentclass[12pt]{minimal} \use…
Simultaneous measurements of thett¯,W+W−, andZ/γ*→ττproduction cross-sections inppcollisions ats=7 TeVwith the ATLAS detector
Simultaneous measurements of the t (t) over bar, W+W-, and Z/gamma* -> tau tau production cross-sections using an integrated luminosity of 4.6 fb(-1) of pp collisions at root s = 7 TeV collected ...
Observation of Higgs boson production in association with a top quark pair at the LHC with the ATLAS detector
Physics letters / B 784, 173 - 191 (2018). doi:10.1016/j.physletb.2018.07.035
Search for high-mass diphoton resonances inppcollisions ats=8 TeVwith the ATLAS detector
Search for high-mass diphoton resonances in pp collisions at pffisffi root s=8 TeV with the ATLAS detector
Search for Quantum Black Hole Production in High-Invariant-MassLepton+JetFinal States UsingppCollisions ats=8 TeVand the ATLAS Detector
This Letter presents a search for quantum black-hole production using 20.3 fb(-1) of data collected with the ATLAS detector in pp collisions at the LHC at root s = 8 TeV. The quantum black holes are assumed to decay into a final state characterized by a lepton (electron or muon) and a jet. In either channel, no event with a lepton-jet invariant mass of 3.5 TeV or more is observed, consistent with the expected background. Limits are set on the product of cross sections and branching fractions for the lepton + jet final states of quantum black holes produced in a search region for invariant masses above 1 TeV. The combined 95% confidence level upper limit on this product for quantum black hol…
Measurement of the production of neighbouring jets in lead–lead collisions at sNN=2.76 TeV with the ATLAS detector
This Letter presents measurements of correlated production of nearby jets in Pb+Pb collisions at root s(NN) = 2.76 TeV using the ATLAS detector at the Large Hadron Collider. The measurement was performed using 0.14 nb(-1)of data recorded in 2011. The production of correlated jet pairs was quantified using the rate, R-Delta R, of "neighbouring" jets that accompany "test" jets within a given range of angular distance, Delta R, in the pseudorapidity-azimuthal angle plane. The jets were measured in the ATLAS calorimeter and were reconstructed using the anti-ktalgorithm with radius parameters d = 0.2, 0.3, and 0.4. R-Delta R was measured in different Pb+Pbcollision centrality bins, characterized…
Performance of $b$-Jet Identification in the ATLAS Experiment
We thank CERN for the very successful operation of the LHC, as well as the support staff from our institutions without whom ATLAS could not be operated efficiently. We acknowledge the support of ANPCyT, Argentina; YerPhI, Armenia; ARC, Australia; BMWFW 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; IN2P3-CNRS, CEA-DSM/IRFU, France; GNSF, Georgia; BMBF, HGF, and MPG, Germany; GSRT, Greece; RGC, Hong Kong SAR, China; ISF, I-CORE and Benoziyo Center, Israel; INFN, Italy; MEXT an…
Centrality, rapidity, and transverse momentum dependence of isolated prompt photon production in lead-lead collisions atsNN=2.76TeV measured with the ATLAS detector
Prompt photon production in root S-NN = 2.76-TeV Pb + Pb collisions has been measured by the ATLAS experiment at the Large Hadron Collider using data collected in 2011 with an integrated luminosity ...
Observation of top-quark pair production in association with a photon and measurement of thett¯γproduction cross section inppcollisions ats=7TeV using the ATLAS detector
A search is performed for top-quark pairs (t (t) over bar) produced together with a photon (gamma) with transverse energy greater than 20 GeV using a sample of t (t) over bar candidate events in final states with jets, missing transverse momentum, and one isolated electron or muon. The data set used corresponds to an integrated luminosity of 4.59 fb(-1) of proton-proton collisions at a center-of-mass energy of 7 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. In total, 140 and 222 t (t) over bar gamma candidate events are observed in the electron and muon channels, to be compared to the expectation of 79 +/- 26 and 120 +/- 39 non-t (t) over bar gamma background events,…