0000000001060048
AUTHOR
T.j. Jones
Measurement of the W→τντ cross section in pp collisions at s=7 TeV with the ATLAS experiment
The cross section for the production of W bosons with subsequent decay W to tau nu is measured with the ATLAS detector at the LHC. The analysis is based on a data sample that was recorded in 2010 at a proton-proton center-of-mass energy of sqrt(s) = 7 TeV and corresponds to an integrated luminosity of 34 pb^-1. The cross section is measured in a region of high detector acceptance and then extrapolated to the full phase space. The product of the total W production cross section and the W to tau nu branching ratio is measured to be 11.1 +/- 0.3 (stat) +/- 1.7 (syst) +/- 0.4 (lumi) nb.
Search for light top squark pair production in final states with leptons and b-jets with the ATLAS detector in s=7 TeV proton–proton collisions
The results of a search for pair production of light top squarks are presented, using 4.7 fb(-1) of root s = 7 TeV proton-proton collisions collected with the ATLAS detector at the Large Hadron Collider. This search targets top squarks with masses similar to, or lighter than, the top quark mass. Final states containing exclusively one or two leptons (e, mu), large missing transverse momentum, light-flavour jets and b-jets are used to reconstruct the top squark pair system. Event-based mass scale variables are used to separate the signal from a large t (t) over bar background. No excess over the Standard Model expectations is found. The results are interpreted in the framework of the Minimal…
Measurement of the differential cross-sections of inclusive, prompt and non-prompt J/ψ production in proton–proton collisions at s=7 TeV
The inclusive J/psi production cross-section and fraction of J/psi mesons produced in B-hadron decays are measured in proton proton collisions at root s = 7 TeV with the ATLAS detector at the LHC, as a function of the transverse momentum and rapidity of the J/psi, using 2.3 pb(-1) of integrated luminosity. The cross-section is measured from a minimum P-T of 1 GeV to a maximum of 70 GeV and for rapidities within vertical bar y vertical bar < 2.4 giving the widest reach of any measurement of J/psi production to date. The differential production cross-sections of prompt and non-prompt J/psi are separately determined and are compared to Colour Singlet NNLO*, Colour Evaporation Model, and FONLL …
Search for a Standard Model Higgs boson in the mass range 200–600 GeV in the H→ZZ→ℓ+ℓ−qq¯ decay channel with the ATLAS detector
A search for a heavy Standard Model Higgs boson decaying via H -> ZZ -> l(+)l(-)q (q) over bar, where l = e or mu, is presented. The search uses a data set of pp collisions at root s = 7 TeV, ...
Search for the Xb and other hidden-beauty states in the π+π−ϒ(1S) channel at ATLAS
This Letter presents a search for a hidden-beauty counterpart of the X(3872) in the mass ranges 10.05--10.31 GeV and 10.40--11.00 GeV, in the channel Xb→π+π−Υ(1S)(→μ+μ−), using 16.2 fb−1 of s√=8 TeV pp collision data collected by the ATLAS detector at the LHC. No evidence for new narrow states is found, and upper limits are set on the product of the Xb cross section and branching fraction, relative to those of the Υ(2S), at the 95% confidence level using the CLS approach. These limits range from 0.8% to 4.0%, depending on mass. For masses above 10.1 GeV, the expected upper limits from this analysis are the most restrictive to date. Searches for production of the Υ(13DJ), Υ(10860), and Υ(110…
Measurement of exclusive γγ→ℓ+ℓ− production in proton–proton collisions at s=7 TeV with the ATLAS detector
This Letter reports a measurement of the exclusive gamma gamma -> l(+)l(-) (l = e, mu) cross-section in proton-proton collisions at a centre-of-mass energy of 7 TeV by the ATLAS experiment at the LHC, based on an integrated luminosity of 4.6 fb(-1). For the electron or muon pairs satisfying exclusive selection criteria, a fit to the dilepton acoplanarity distribution is used to extract the fiducial cross-sections. The cross-section in the electron channel is determined to be sigma(excl)(gamma gamma -> e+e-) = 0.428 +/- 0.035 (stat.) +/- 0.018 (syst.) pbfor a phase-space region with invariant mass of the electron pairs greater than 24GeV, in which both electrons have transverse momentum p(T)…
Measurement of the cross-section for b-jets produced in association with a Z boson at s=7 TeV with the ATLAS detector
A measurement is presented of the inclusive cross-section for b-jet production in association with a Z boson in pp collisions at a centre-of-mass energy of root s = 7 TeV. The analysis uses the data sample collected by the ATLAS experiment in 2010, corresponding to an integrated luminosity of approximately 36 pb(-1). The event selection requires a Z boson decaying into high P-T electrons or muons, and at least one b-jet, identified by its displaced vertex, with transverse momentum p(T) > 25 GeV and rapidity vertical bar y vertical bar < 2.1. After subtraction of background processes, the yield is extracted from the vertex mass distribution of the candidate b-jets. The ratio of this cross-se…
Measurement of the transverse momentum distribution of Z/γ⁎ bosons in proton–proton collisions at s=7 TeV with the ATLAS detector
A measurement of the Z/gamma* transverse momentum (p(T)(Z)) distribution in proton-proton collisions at root s = 7 TeV is presented using Z/gamma* -> e(+)e(-) and Z/gamma* -> mu(+)mu(-) decay ...
Search for neutral Higgs bosons from supersymmetry in Z decays
The light scalar Higgs boson h and the pseudoscalar Higgs boson A of the minimal supersymmetric standard model have been searched for in the processes e+e−→hff and e+e−→hA using data collected by ALEPH at the LEP e+e− collider, with center of mass energies at and near the Z peak. Using a variety of signatures adapted to various mass ranges for h and A, we have excluded a large domain in the parameter space. For large values of ν2ν1, the ratio of the vacuum expectation values of the two Higgs fields, the whole range from 0 to 38.8 GeV is excluded for Mh and MA at 95% CL.
Measurement of the b → τ-ν̄τX branching ratio
The definitions of “anthropology” found in various dictionaries cover a whole range of terms and in this section we provide an overview of all its connotations. In this way a variety of reflections about the essence of man become possible, for instance as : summit of creation; source of his own values; specific biological reality; intelligence (but what is this, really?); knowing subject or object of knowledge; social being and product of a culture. Following these lines of thought one realises that all these preoccupations have already been taken up, or at least touched upon, by communication theory.
Search for new physics in the dijet mass distribution using 1 fb−1 of pp collision data at s=7 TeV collected by the ATLAS detector
Invariant mass distributions of jet pairs (dijets) produced in LHC proton-proton collisions at a centre-of-mass energy root s = 7 TeV have been studied using a data set corresponding to an integrat ...
Searches for the standard Higgs boson
Abstract A data sample corresponding to about 100 000 hadronic Z decays collected by ALEPH at LEP has been used to search for the standard Higgs boson produced in the reaction e + e − → H 0 Z 0∗ . No indication for any signal was found, and a 95% CL lower limit on the Higgs boson mass has been set at 41.6 GeV.
Measurement of the cross section for the production of a W boson in association with b-jets in pp collisions at s=7 TeV with the ATLAS detector
A measurement is presented of the cross section for the production of a W boson with one or two jets, of which at least one must be a b-jet, in pp collisions at root s = 7 TeV. Production via top d ...
Measurement of the top quark pair production cross section in pp collisions at s=7 TeV in dilepton final states with ATLAS
A measurement of the production cross section of top quark pairs (ttbar) in proton-proton collisions at a center-of-mass energy of 7 TeV recorded with the ATLAS detector at the Large Hadron Collider is reported. Candidate events are selected in the dilepton topology with large missing transverse energy and at least two jets. Using a data sample corresponding to an integrated luminosity of 35 pb^-1, a ttbar production cross section of 171 +/- 20(stat.) +/- 14(syst.) +8-6(lum.) pb is measured for an assumed top quark mass of 172.5 GeV. A second measurement requiring at least one jet identified as coming from a b quark yields a comparable result, demonstrating that the dilepton final states ar…
Search for high mass photon pairs in (f= e, μ, τ, v, q) at LEP
Abstract The result of a search for high mass photon pairs from the processes e + e − → f f γγ (f = e, μ, τ, v and q) with the ALEPH detector is reported. The result for f = e , μ and τ is to be compared with the observation of 4 events by the L3 Collaboration with invariant masses, M γγ , of the two photons near 60 GeV. From a data sample approximately twice as large taken from 1990 to 1992, 6 events are found with M γγ distributed between 50 GeV and 72 GeV, while 4.9 events are expected from a QED calculation. There is no evidence for a mass peak; only one event ( μ + μ − γγ ) at M γγ = 59.4 ± 0.2 GeV is compatible with the L3 observation. In addition, for M γγ > 50 GeV, no event is found…
Search for the Standard Model Higgs boson in the decay channel H→ZZ(⁎)→4ℓ with the ATLAS detector
A search for the Standard Model Higgs boson in the decay channel H -> ZZ(()*()) l(+)l(-)l'l'(-), where l = e, mu, is presented. Proton-proton collision data at root s = 7 TeV recorded with the A ...
Search for a new weakly interacting particle
Abstract A search for events of the type e + e − →l + l − X 0 , where X 0 can be any weakly interacting particle which couples to the Z, has been performed with the ALEPH detector at LEP, by searching for acollinear lepton pairs. Such particles can be excluded up to a mass of 7.0 GeV/c 2 for a value of the ratio of branching fractions, Br( Z →X 0 l + l − )/Br(Z→ l + l − ), greater than 2.5 × 10 −3 if the X 0 has third component of isospin, I 3 greater than 1 2 and decays to a pair of virtual gauge bosons. When this analysis is combined with the previous results of the Higgs particle searches from ALEPH, this limit can be extended to an X 0 mass of 60 GeV/c 2 .
Measurement of the t-channel single top-quark production cross section in pp collisions at s=7 TeV with the ATLAS detector
We report a measurement of the cross section of single top-quark production in the t-channel using 1.04 fb -1 of pp collision data at s=7 TeV recorded with the ATLAS detector at the LHC. Selected e ...
Search for diphoton events with large missing transverse momentum in 1 fb−1 of 7 TeV proton–proton collision data with the ATLAS detector
A search for diphoton events with large missing transverse momentum has been performed using 1.07 fb(-1) of proton-proton collision data at root s = 7 TeV recorded with the ATLAS detector. No excess of events was observed above the Standard Model prediction and 95% Confidence Level (CL) upper limits are set on the production cross section for new physics. The limits depend on each model parameter space and vary as follows: sigma < (22-129) fb in the context of a generalised model of gauge-mediated supersymmetry breaking (GGM) with a bino-like lightest neutralino, sigma < (27-91) fb in the context of a minimal model of gauge-mediated supersymmetry breaking (SPS8), and sigma < (15-27) fb in t…
Search for first generation scalar leptoquarks in pp collisions at s=7 TeV with the ATLAS detector
We report a search for first generation scalar leptoquarks using 1.03 fb(-1) of proton-proton collisions data produced by the Large Hadron Collider at root s = 7 TeV and recorded by the ATLAS experiment. Leptoquarks are sought via their decay into an electron or neutrino and a quark, producing events with two oppositely charged electrons and at least two jets, or events with an electron, missing transverse momentum and at least two jets. Control data samples are used to validate background predictions from Monte Carlo simulation. In the signal region, the observed event yields are consistent with the background expectations. We exclude at 95% confidence level the production of first generat…
Search for excited leptons in Z0 decay
Due to the severity of system-wide power outages, though their probability of occurrence is slight, regulatory authorities require that a system restoration plan be drawn up and kept up to date at all times. The power outage that affected northeastern North America in 2003 proved the need for such a requirement. The particular structure of Hydro-Quebec's power system requires the use of a highly specific system restoration procedure. The daily preparation of the system restoration plan is based on a strategy whose application requires that a restoration sequence be drawn up that uses available equipment, the electrical behavior of which has been validated using appropriate studies. Over the…
Measurement of angular correlations in Drell–Yan lepton pairs to probe Z/γ⁎ boson transverse momentum at s=7 TeV with the ATLAS detector
A measurement of angular correlations in Drell-Yan lepton pairs via the phi(eta)* observable is presented. This variable probes the same physics as the Z/gamma* boson transverse momentum with a better experimental resolution. The Z/gamma* -> e(+)e(-) and Z/gamma* -> mu(+)mu(-) decays produced in proton-proton collisions at a centre-of-mass energy of root s = 7 TeV are used. The data were collected with the ATLAS detector at the LHC and correspond to an integrated luminosity of 4.6 fb(-1). Normalised differential cross sections as a function of phi(eta)* are measured separately for electron and muon decay channels. These channels are then combined for improved accuracy. The cross section is …
Searches for heavy long-lived sleptons and R-hadrons with the ATLAS detector in pp collisions at
A search for long-lived particles is performed using a data sample of 4.7 fb(-1) from proton-proton collisions at a centre-of-mass energy. root s = 7 TeV collected by the ATLAS detector at the LHC. No excess is observed above the estimated background and lower limits, at 95% confidence level, are set on the mass of the long-lived particles in different scenarios, based on their possible interactions in the inner detector, the calorimeters and the muon spectrometer. Long-lived staus in gauge-mediated SUSY-breaking models are excluded up to a mass of 300 GeV for tan beta = 5-20. Directly produced long-lived sleptons are excluded up to a mass of 278 GeV. R-hadrons, composites of gluino (stop, …
Measurement of the top quark pair cross section with ATLAS in pp collisions at s=7 TeV using final states with an electron or a muon and a hadronically decaying τ lepton
Measurement of the top quark pair cross section with ATLAS in pp collisions at root s=7 TeV using final states with an electron or a muon and a hadronically decaying tau lepton
Search for supersymmetric particles using acoplanar charged-particle pairs from Z0 decays
We have performed a search for supersymmetric particles using acoplanar pairs of oppositely-charged particles in decays of the Z0. In 0.53 pb−1 of integrated luminosity near the Z0 peak, we observe two events where approximately four are expected from background, allowing limits to be extended on combined photino and slepton masses, and also on combined photino and chargino masses.
Search for new phenomena with the monojet and missing transverse momentum signature using the ATLAS detector in s=7TeV proton–proton collisions
A search for new phenomena in events featuring a high energy jet and large missing transverse momentum in proton-proton collisions at root s = 7 TeV is presented using a dataset corresponding to an integrated luminosity of 33 pb(-1) recorded with the ATLAS detector at the Large Hadron Collider. The number of observed events is consistent with the Standard Model prediction. This result is interpreted in terms of limits on a model of Large Extra Dimensions. (C) 2011 CERN. Published by Elsevier B.V. All rights reserved.
High-ET isolated-photon plus jets production in pp collisions at s=8 TeV with the ATLAS detector
The dynamics of isolated-photon plus one-, two- and three-jet production in pp collisions at a centre-of-mass energy of 8 TeV are studied with the ATLAS detector at the LHC using a data set with an ...
Search for the Higgs boson in the H→WW→ℓνjj decay channel at s=7 TeV with the ATLAS detector
A search for the Standard Model Higgs boson has been performed in the H→WW→lνjj channel using 4.7 fb^(−1) of pp collision data recorded at a centre-of-mass energy of √s = 7 TeV with the ATLAS detector at the Large Hadron Collider. Higgs boson candidates produced in association with zero, one or two jets are included in the analysis to maximize the acceptance for both gluon fusion and weak boson fusion Higgs boson production processes. No significant excess of events is observed over the expected background and limits on the Higgs boson production cross section are derived for a Higgs boson mass in the range 300 GeV<m_H<600 GeV. The best sensitivity is reached for m_H=400 GeV, where the obse…
Measurement of the pseudorapidity and transverse momentum dependence of the elliptic flow of charged particles in lead–lead collisions at sNN=2.76 TeV with the ATLAS detector
This Letter describes the measurement of elliptic flow of charged particles in lead-lead collisions at root s(NN) = 2.76 TeV using the ATLAS detector at the Large Hadron Collider (LHC). The results ...
Search for decays of the Z0 into a photon and a pseudoscalar meson
Abstract A search is reported for decays of the Z 0 into π 0 γ , ηγ and η ′ (958) γ in e + e − collisions using data collected during a scan around the Z 0 mass. In order to search for π 0 γ final states, in which the two photons from the π 0 decay are unresolved, the production of pairs of high-energy electromagnetic clusters is studied. The data are compared with the expectations from the pure QED process e + e − → γγ , and a 95% confidence level upper limit on the branching ratio of the Z 0 into π 0 γ of 4.9 × 10 −4 is derived. For η′γ, the decay modes of the mesons that contain two charged particles are largely free from QED background. These modes are used to place upper limits of 4.6 …
Search for direct slepton and gaugino production in final states with two leptons and missing transverse momentum with the ATLAS detector in pp collisions at
A search for the electroweak pair production of charged sleptons and weak gauginos decaying into final states with two leptons is performed using 4.7 fb(-1) of proton-proton collision data at root s = 7 TeV recorded with the ATLAS experiment at the Large Hadron Collider. No significant excesses are observed with respect to the prediction from Standard Model processes. In the scenario of direct slepton production, if the sleptons decay directly into the lightest neutralino, left-handed slepton masses between 85 and 195 GeV are excluded at 95% confidence level for a 20 GeV neutralino. Chargino masses between 110 and 340 GeV are excluded in the scenario of direct production of wino-like chargi…
Measurement of the and B− meson lifetimes
Abstract The lifetimes of the B 0 and B − mesons have been measured with the ALEPH detector at LEP. Semileptonic decays of B 0 and B − mesons were partially reconstructed by identifying events containing a lepton with an associated D ∗+ or D 0 meson. The proper time of the B meson was estimated from the measured decay length and the momentum and mass of the D -lepton system. A fit to the proper time of 77 D ∗+ l − and 77 D 0 l − candidates, combined with a constraint on the lifetime ratio ( τ − τ 0 ) arising from the relative rates of observed D ∗+ l − and D 0 l − events, yielded the following lifetimes: τ 0 =1.52 −0.18 +0.20 ( stat. ) −0.13 +0.07 ( syst. ) ps , τ − = 1.47 −0.19 +0.22 ( sta…
Charged-particle multiplicities in pp interactions at s=900 GeV measured with the ATLAS detector at the LHC
The first measurements from proton-proton collisions recorded with the ATLAS detector at the LHC are presented. Data were collected in December 2009 using a minimum-bias trigger during collisions at a centre-of-mass energy of 900 GeV. The charged-particle multiplicity, its dependence on transverse momentum and pseudorapidity, and the relationship between mean transverse momentum and charged-particle multiplicity are measured for events with at least one charged particle in the kinematic range vertical bar eta vertical bar 500 MeV. The measurements are compared to Monte Carlo models of proton-proton collisions and to results from other experiments at the same centre-of-mass energy. The charg…
Search for the Standard Model Higgs boson in the H→WW(⋆)→ℓνℓν decay mode with 4.7 fb−1 of ATLAS data at s=7 TeV
A search for the Standard Model Higgs boson in the H -> WW(*()) -> lvlv (l = e.mu) decay mode is presented. The search is performed using proton-proton collision data corresponding to an inte ...
Search for a standard model Higgs boson in the H→ZZ→ℓ+ℓ−νν¯ decay channel using 4.7 fb−1 of s=7 TeV data with the ATLAS detector
A search for a Standard Model Higgs boson decaying via H -> ZZ -> l(+)l(-) nu(nu) over bar, where l represents electrons or muons, is presented. It is based on proton-proton collision data at ...
Search for excited neutrinos in Z decay
Excited neutrinos decaying into a neutrino and a photon are searched for in the ALEPH detector at LEP. No evidence is found for Z decay into vv∗ or v∗v∗ final states. Upper limits are derived on excited neutrino couplings up to excited neutrino masses close to the Z mass. Lower limits on the v∗ mass, independent of the v∗ decay modes, are deduced from the total Z width.
Search for a heavy narrow resonance decaying to eμ, eτ, or μτ with the ATLAS detector in s=7 TeV pp collisions at the LHC
This Letter presents the results of a search for a heavy particle decaying into an e^±μ^∓e^±μ^∓, or μ^±τ^∓ final state in pp collisions at View the MathML sources=7 TeV. The data were recorded with the ATLAS detector at the LHC during 2011 and correspond to an integrated luminosity of 4.6 fb−14.6 fb^(−1). No significant excess above the Standard Model expectation is observed, and exclusions at 95% confidence level are placed on the cross section times branching ratio for the production of an R-parity-violating supersymmetric tau sneutrino. For a sneutrino mass of 500 (2000) GeV, the observed limits on the production cross section times branching ratio are 3.2 (1.4) fb, 42 (17) fb, and 40 (1…
Search for long-lived, heavy particles in final states with a muon and multi-track displaced vertex in proton–proton collisions at s=7 TeV with the ATLAS detector
Many extensions of the Standard Model posit the existence of heavy particles with long lifetimes. In this Letter, results are presented of a search for events containing one or more such particles, which decay at a significant distance from their production point, using a final state containing charged hadrons and an associated muon. This analysis uses a data sample of proton-proton collisions at root s = 7 TeV corresponding to an integrated luminosity of 4.4 fb(-1) collected in 2011 by the ATLAS detector operating at the Large Hadron Collider. Results are interpreted in the context of R-parity violating supersymmetric scenarios. No events in the signal region are observed and limits are se…
Search for FCNC single top-quark production at s=7 TeV with the ATLAS detector
A search for the production of single top-quarks via flavour-changing neutral-currents is presented. Data collected with the ATLAS detector at a centre-of-mass energy of root s = 7 TeV, correspondi ...
Measurement of the strong coupling constant using τ decays
The strong coupling constant is determined from the leptonic branching ratios, the lifetime, and the invariant mass distribution of the hadronic final state of the tau lepton, using data accumulated at LEP with the ALEPH detector. The strong coupling constant measurement, alpha(s), (m(tau)2) = 0.330 +/-0.046, evolved to the Z mass, yields alpha(s)(M(Z)2) = 0. 1 18 +/- 0.005. The error includes experimental and theoretical uncertainties, the latter evaluated in the framework of the Shifman, Vainshtein and Zakharov (SVZ) approach. The method allows the non-perturbative contribution to the hadronic decay rate to be determined to be 0.3 +/- 0.5% . RI Perrier, Frederic/A-5953-2011; ANTONELLI, AN…
Measurement of the centrality dependence of J/ψ yields and observation of Z production in lead–lead collisions with the ATLAS detector at the LHC
Using the ATLAS detector, a centrality-dependent suppression has been observed in the yield of J/psi mesons produced in the collisions of lead ions at the Large Hadron Collider. In a sample of minimum-bias lead-lead collisions at a nucleon-nucleon centre of mass energy root s(NN) = 2.76 TeV, corresponding to an integrated luminosity of about 6.7 mu b(-1), J/psi mesons are reconstructed via their decays to mu(+)mu(-) pairs. The measured J/psi yield, normalized to the number of binary nucleon-nucleon collisions, is found to significantly decrease from peripheral to central collisions. The centrality dependence is found to be qualitatively similar to the trends observed at previous, lower ener…
Production and decay of charmed mesons at the Z resonance
Abstract In a sample of 190 000 hadronic Z decays, three signals of charm production are observed: two from the exclusive decays D ° → K − π + and D ∗+ → D °π + → K − π + π + and one in the transverse-momentum distribution of soft hadrons relative to the nearest jet. The features of these signals are in good agreement with expectations based on the standard model and previous measurements of the branching fractions. The number of D ∗± → K ± π ± π ± per hadronic decay of the Z is measured to be (5.11±0.34) × 10 −3 , and the branching ratio B(D 0 → K − π + ) is (3.62 ± 0.34 ± 0.44)%. Charm hadronization has been studied. The average fraction of the beam energy carried by the D ∗ meson is foun…
Measurement of D⁎±, D± and Ds± meson production cross sections in pp collisions at s=7 TeV with the ATLAS detector
The production of D*(+/-), D-+/- and D-S(+/-) charmed mesons has been measured with the ATLAS detector in pp collisions at,/7s = 7 TeV at the LHC, using data corresponding to an integrated luminosi ...
Measurement of the production cross section for W-bosons in association with jets in pp collisions at s=7 TeV with the ATLAS detector
This Letter reports on a first measurement of the inclusive W + jets cross section in proton-proton collisions at a centre-of-mass energy of 7 TeV at the LHC, with the ATLAS detector. Cross section ...
Search for Diphoton Events with Large Missing Transverse Energy with 36 pb^-1 of 7 TeV Proton-Proton Collision Data with the ATLAS Detector
Making use of 36 pb^-1 of proton-proton collision data at sqrt{s} = 7 TeV, the ATLAS Collaboration has performed a search for diphoton events with large missing transverse energy. Observing no excess of events above the Standard Model prediction, a 95% Confidence Level (CL) upper limit is set on the cross section for new physics of sigma < 0.38 - 0.65 pb in the context of a generalised model of gauge mediated supersymmetry breaking (GGM) with a bino-like lightest neutralino, and of sigma < 0.18 - 0.23 pb in the context of a specific model with one universal extra dimension (UED). A 95 % CL lower limit of 560 GeV, for bino masses above 50 GeV, is set on the GGM gluino mass, while a low…
Search for squarks and gluinos using final states with jets and missing transverse momentum with the ATLAS detector in s=7 TeV proton–proton collisions
A search for squarks and gluinos in events containing jets, missing transverse momentum and no electrons or muons is presented. The data were recorded in 2011 by the ATLAS experiment in root s = 7 TeV proton-proton collisions at the Large Hadron Collider. No excess above the Standard Model background expectation is observed in 1.04 fb(-1) of data. Gluino and squark masses below 700 GeV and 875 GeV respectively are excluded at the 95% confidence level in simplified models containing only squarks of the first two generations, a gluino octet and a massless neutralino. The exclusion limit increases to 1075 GeV for squarks and gluinos of equal mass. In MSUGRA/CMSSM models with tan beta = 10, A(0…
Measurement of the inclusive isolated prompt photon cross-section in pp collisions at s=7 TeV using 35 pb−1 of ATLAS data
A measurement of the differential 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 cove ...
Search for long-lived, multi-charged particles in pp collisions at s=7 TeV using the ATLAS detector
A search for highly ionising, penetrating particles with electric charges from |q| = 2e to 6e is performed using the ATLAS detector at the CERN Large Hadron Collider. Proton-proton collision data taken at sqrt(s)=7 TeV during the 2011 running period, corresponding to an integrated luminosity of 4.4 fb^-1, are analysed. No signal candidates are observed, and 95% confidence level cross-section upper limits are interpreted as mass-exclusion lower limits for a simplified Drell--Yan production model. In this model, masses are excluded from 50 GeV up to 430, 480, 490, 470 and 420 GeV for charges 2e, 3e, 4e, 5e and 6e, respectively.
Two-particle azimuthal correlations in photonuclear ultraperipheral Pb+Pb collisions at 5.02 TeV with ATLAS
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 and ANID, Chile, CAS, MOST, and NSFC, China, COLCIENCIAS, Colombia, MSMT CR, MPO CR, and VSC CR, Czech Republic, DNRF and DNSRC, Denmark, IN2P3-CNRS and CEA-DRF/IRFU, France, SRNSFG, Georgia, BMBF, HGF, and MPG, Germany, GSRT, Greece, RGC and Hong Kong SAR, China, ISF and Benoziyo Center, Israel, INFN, Italy, MEXT and JSPS, Japan, CNR…
Measurement of Wγ and Zγ production cross sections in pp collisions at s=7 TeV and limits on anomalous triple gauge couplings with the ATLAS detector
This Letter presents measurements of l(+/-) nu gamma and l(+)l(-)gamma (l = e.mu) production in 1.02 fb(-1) of pp collision data recorded at root s = 7 TeV with the ATLAS detector at the LHC in the ...
ALEPH: a Detector for Electron-Positron Annihilations at LEP
Process-centred Software Engineering Environments (PSEE) are the most recent generation of environments supporting software development activities. Most of PSEE are based on mechanisms promoting enforcement and automation of process activities. In this kind of mechanisms the process models are prescribed in a detailed and complete way. But the experience shows that supporting processes is more concerned with the flexibility of guidance offered during the process performance than with enforcement of a collection of predefined process models. In this paper, we present a solution to support strategic processes in a PSEE by providing a flexible guidance during process enactment.
Search for a heavy Standard Model Higgs boson in the channel H→ZZ→ℓ+ℓ−qq¯ using the ATLAS detector
A search for a heavy Standard Model Higgs boson decaying via H -> ZZ -> l(+)l(-)q (q) over bar, where l = e, mu, is presented. The search is performed using a data set of pp collisions at root s = 7 TeV, corresponding to an integrated luminosity of 1.04 fb(-1) collected in 2011 by the ATLAS detector at the CERN LHC collider. No significant excess of events above the estimated background is found. Upper limits at 95% confidence level on the production cross section (relative to that expected from the Standard Model) of a Higgs boson with a mass in the range between 200 and 600 GeV are derived. Within this mass range, there is at present insufficient sensitivity to exclude a Standard Model Hi…
Measurements of the electron and muon inclusive cross-sections in proton–proton collisions at s=7 TeV with the ATLAS detector
This Letter presents measurements of the differential cross-sections for inclusive electron and muon production in proton-proton collisions at a centre-of-mass energy of root s = 7 TeV, using data collected by the ATLAS detector at the LHC. The muon cross-section is measured as a function of p(T) in the range 4 < p(T) < 100 GeV and within pseudorapidity vertical bar eta vertical bar < 2.5. In addition the electron and muon cross-sections are measured in the range 7 < p(T) < 26 GeV and within vertical bar eta vertical bar < 2.0, excluding 1.37 < vertical bar eta vertical bar < 1.52. Integrated luminosities of 1.3 pb(-1) and 1.4 pb(-1) are used for the electron and muon measurements, respecti…
Search for supersymmetry in pp collisions at s=7 TeV in final states with missing transverse momentum and b-jets
Results are presented of a search for supersymmetric particles in events with large missing transverse momentum and at least one heavy flavour jet candidate in sqrt{s} = 7 TeV proton-proton collisions. In a data sample corresponding to an integrated luminosity of 35 pb-1 recorded by the ATLAS experiment at the Large Hadron Collider, no significant excess is observed with respect to the prediction for Standard Model processes. For R-parity conserving models in which sbottoms (stops) are the only squarks to appear in the gluino decay cascade, gluino masses below 590 GeV (520 GeV) are excluded at the 95% C.L. The results are also interpreted in an MSUGRA/CMSSM supersymmetry breaking scenario w…
Search for single b⁎-quark production with the ATLAS detector at s=7 TeV
The results of a search for an excited bottom-quark b* in pp collisions at root s = 7 TeV, using 4.7 fb(-1) of data collected by the ATLAS detector at the LHC are presented. In the model studied, a ...
Transverse momentum, rapidity, and centrality dependence of inclusive charged-particle production in sNN=5.02 TeV p+ Pb collisions measured by the ATLAS experiment
Measurements of the per-event charged-particle yield as a function of the charged-particle transverse momentum and rapidity are performed using p+Pbp+Pb collision data collected by the ATLAS experiment at the LHC at a centre-of-mass energy of sqrt (SNN) = 5.01 TeV. Charged particles are reconstructed over pseudorapidity |η|<2.3|η|<2.3 and transverse momentum between 0.1 GeV0.1 GeV and 22 GeV22 GeV in a dataset corresponding to an integrated luminosity of 1 μb−11 μb−1. The results are presented in the form of charged-particle nuclear modification factors, where the p+Pbp+Pb charged-particle multiplicities are compared between central and peripheral p+Pbp+Pb collisions as well as to charged-p…
Measurement of the B hadron lifetime
The average lifetime of B hadrons has been measured by the ALEPH experiment at LEP. Events containing B hadrons are selected by the identification of leptons with high transverse momentum in hadronic Z decays, and the lifetime is extracted from a fit to the impact parameter distribution of the lepton tracks. From a sample of 1.7×105 hadronic Z decays a lifetime of 1.29±0.06±0.10 ps is measured.
Measurement of B- mixing at the Z
Abstract From more than 175 000 hadronic Z decays observed with the ALEPH detector at LEP, we select 823 events with pairs of leptons in the final state. From these we measure χ , the probability thata b hadron which is observed to decay originated as a b hadron. We find χ =0.132 −0.026 +0.027 .
Measurement of the strong coupling constant alfa_s from global event-shape variables of hadronic Z decays
Abstract An analysis of global event-shape variables has been carried out for the reaction e+e−→Z0→hadrons to measure the strong coupling constant αs. This study is based on 52 720 hadronic events obtained in 1989/90 with the ALEPH detector at the LEP collider at energies near the peak of the Z-resonance. In order to determine αs, second order QCD predictions modified by effects of perturbative higher orders and hadronization were fitted to the experimental distributions of event-shape variables. From a detailed analysis of the theoretical uncertainties we find that this approach is best justified for the differential two-jet rate, from which we obtain αs(MZ2) = 0.121 ± 0.002(stat.)±0.003(s…
A measurement of the ratio of the W and Z cross sections with exactly one associated jet in pp collisions at with ATLAS
The ratio of production cross sections of the W and Z bosons with exactly one associated jet is presented as a function of jet transverse momentum threshold. The measurement has been designed to ma ...
Search for pair production of heavy top-like quarks decaying to a high-pT W boson and a b quark in the lepton plus jets final state at s=7 TeV with the ATLAS detector
A search is presented for production of a heavy up-type quark (t') together with its antiparticle, assuming a significant branching ratio for subsequent decay into a W boson and a b quark. The search is based on 4.7 fb(-1) of pp collisions root s = 7 TeV recorded in 2011 with the ATLAS detector at the CERN Large Hadron Collider. Data are analyzed in the lepton + jets final state, characterized by a high-transverse-momentum isolated electron or muon, large missing transverse momentum and at least three jets. The analysis strategy relies on the substantial boost of the W bosons in the t'(t') over bar signal when m(t') greater than or similar to 400 GeV. No significant excess of events above t…