Papers by R. Asfandiyarov
Search for supersymmetry with jets, missing transverse momentum and at least one hadronically dec... more Search for supersymmetry with jets, missing transverse momentum and at least one hadronically decaying τ lepton in proton-proton collisions at √ s = 7 TeV with the ATLAS detector ✩ .ATLAS Collaboration a r t i c l e i n f o a b s t r a c t A search for production of supersymmetric particles in final states containing jets, missing transverse momentum, and at least one hadronically decaying τ lepton is presented. The data were recorded by the ATLAS experiment in √ s = 7 TeV proton-proton collisions at the Large Hadron Collider. No excess above the Standard Model background expectation was observed in 2.05 fb −1 of data. The results are interpreted in the context of gauge mediated supersymmetry breaking models with M mess = 250 TeV, N 5 = 3, μ > 0, and C grav = 1. The production of supersymmetric particles is excluded at 95% C.L. up to a supersymmetry breaking scale Λ = 30 TeV, independent of tan β, and up to Λ = 43 TeV for large tan β.
A measurement of the production cross-section for top quark pairs (tt) in pp collisions at √ s = ... more A measurement of the production cross-section for top quark pairs (tt) 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 two different topologies: single lepton (electron e or muon μ) with large missing transverse energy and at least four jets, and dilepton (ee, μμ or eμ) with large missing transverse energy and at least two jets. In a data sample of 2.9 pb −1 , 37 candidate events are observed in the single-lepton topology and 9 events in the dilepton topology. The corresponding expected backgrounds from non-tt Standard Model processes are estimated using data-driven methods and determined to be 12.2 ± 3.9 events and 2.5 ± 0.6 events, respectively. The kinematic properties of the selected events are consistent with SM tt production. The inclusive top quark pair production cross-section is measured to be σ tt = 145 ± 31(stat.) +42 −27 (syst.) pb.
Physics Letters B, 2012
The results of a search for pair production of light top squarks are presented, using 4.7 fb −1 o... more The results of a search for pair production of light top squarks are presented, using 4.7 fb −1 of √ 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, µ), 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 tt background. No excess over the Standard Model expectations is found. The results are interpreted in the framework of the Minimal Supersymmetric Standard Model, assuming the top squark decays exclusively to a chargino and a b-quark, while requiring different mass relationships between the Supersymmetric particles in the decay chain. Light top squarks with masses between 123-167 GeV are excluded for neutralino masses around 55 GeV.
Physics Letters B, 2012
ScienceDirect; Scopus; Applications. Register; Login Login; Go to SciVal Suite. Username: Passwor... more ScienceDirect; Scopus; Applications. Register; Login Login; Go to SciVal Suite. Username: Password: Remember me. | Not Registered? Forgotten your username or password? Go to Athens / Institution login. Home; Publications; Search; My settings; My alerts. Help. Export citation. PDF (4307 K). More options... Email article. Signed up for journal alerts [remove]. Alert me about new articles in this journal. Your selection(s) could not be saved due to an internal error. Please try again. Show thumbnail images. Search. Articles Articles, All fields, Author, Advanced ...
Journal of High Energy Physics, 2012
Measurement of the cross section for the production of a W boson in association with b-jets in pp... more 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 ✩ .ATLAS Collaboration a r t i c l e i n f o a b s t r a c t 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 √ s = 7 TeV. Production via top decay is not included in the signal definition. The measurement is based on 35 pb −1 of data collected with the ATLAS detector at the LHC. The W + b-jet cross section is defined for jets reconstructed with the antik t clustering algorithm with transverse momentum above 25 GeV and rapidity within ±2.1. The b-jets
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 2011
√ s = 7 TeV measured with the ATLAS detector ✩ .ATLAS Collaboration a r t i c l e i n f o a b s t... more √ s = 7 TeV measured with the ATLAS detector ✩ .ATLAS Collaboration a r t i c l e i n f o a b s t r a c t Dijet angular distributions from the first LHC pp collisions at center-of-mass energy √ s = 7 TeV have been measured with the ATLAS detector. The dataset used for this analysis represents an integrated luminosity of 3.1 pb −1 . Dijet χ distributions and centrality ratios have been measured up to dijet masses of 2.8 TeV, and found to be in good agreement with Standard Model predictions. Analysis of the χ distributions excludes quark contact interactions with a compositeness scale Λ below 3.4 TeV, at 95% confidence level, significantly exceeding previous limits. √ s = 7 TeV at the LHC. The data sample represents an integrated luminosity of 3.1 pb −1 , recorded in periods of stable collisions, through August 2010. The two distributions under
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 2011
The ATLAS detector at the LHC is used to search for high-mass states, such as heavy charged gauge... more The ATLAS detector at the LHC is used to search for high-mass states, such as heavy charged gauge bosons (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 ...
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 2011
Using the ATLAS detector, a centrality-dependent suppression has been observed in the yield of J/... more Using the ATLAS detector, a centrality-dependent suppression has been observed in the yield of J/ψ 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 √ s N N = 2.76 TeV, corresponding to an integrated luminosity of about 6.7 µb −1 , J/ψ mesons are reconstructed via their decays to µ + µ − pairs. The measured J/ψ 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 energy experiments. The same sample is used to reconstruct Z bosons in the µ + µ − final state, and a total of 38 candidates are selected in the mass window of 66 to 116 GeV. The relative Z yields as a function of centrality are also presented, although no conclusion can be inferred about their scaling with the number of binary collisions, because of limited statistics. This analysis provides the first results on J/ψ and Z production in lead-lead collisions at the LHC.
Physical Review Letters, 2012
Abstract This document presents a search for the production of supersymmetric particles decaying ... more Abstract This document presents a search for the production of supersymmetric particles decaying into final states with three electrons or muons and missing transverse momentum. The analysis uses 2.06 fb− 1 of√ s= 7 TeV proton-proton collision data delivered by the ...
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 2012
The results of a search for pair production of the lighter scalar partners of top quarks (t˜ 1) i... more The results of a search for pair production of the lighter scalar partners of top quarks (t˜ 1) in 2.05 fb− 1 of pp collisions at s= 7 TeV using the ATLAS experiment at the LHC are reported. Scalar top quarks are searched for in events with two same flavour opposite-sign leptons (e, μ) with invariant mass consistent with the Z boson mass, large missing transverse momentum and jets in the final state. At least one of the jets is identified as originating from a b-quark. No excess over Standard Model expectations is found. The results are ...
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 2012
Search for new particles decaying to ZZ using final states with leptons and jets with the ATLAS d... more 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 ✩ .ATLAS Collaboration a r t i c l e i n f o a b s t r a c t 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 √ s = 7 TeV.
European Physical Journal C, 2012
A search is presented for the pair production of light scalar top quarks in sqrt (s)= 7 TeV proto... more A search is presented for the pair production of light scalar top quarks in sqrt (s)= 7 TeV proton-proton collisions recorded with the ATLAS detector at the Large Hadron Collider. This analysis uses the full data sample collected during 2011 that corresponds to a total integrated luminosity of 4.7 fb-1. Light scalar top quarks are searched for in events with two opposite-sign leptons (e, mu), large missing transverse momentum and at least one jet in the final state. No excess over Standard Model expectations is found, and the results are ...
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 2012
This Letter presents a search for contact interactions in the dielectron and dimuon channels usin... more This Letter presents a search for contact interactions in the dielectron and dimuon channels using data from proton–proton collisions produced by the LHC at s= 7 TeV and recorded by the ATLAS detector. The data sample, collected in 2011, corresponds to an integrated luminosity of 1.08 and 1.21 fb− 1 in the e+ e− and μ+ μ− channels, respectively. No significant deviations from the standard model are observed. Using a Bayesian approach with a prior flat in 1/Λ2, the following 95% CL lower limits are placed on the energy scale ...
European Physical Journal C, 2012
The measurement of missing transverse momentum in the ATLAS detector, described in this paper, ma... more The measurement of missing transverse momentum in the ATLAS detector, described in this paper, makes use of the full event reconstruction and a calibration based on reconstructed physics objects. The performance of the missing transverse momentum reconstruction is evaluated using data collected in pp collisions at a centre-of-mass energy of 7 TeV in 2010. Minimum bias events and events with jets of hadrons are used from data samples corresponding to an integrated luminosity of about 0.3 nb −1 and 600 nb −1 respectively, together with events containing a Z boson decaying to two leptons (electrons or muons) or a W boson decaying to a lepton (electron or muon) and a neutrino, from a data sample corresponding to an integrated luminosity of about 36 pb −1 . An estimate of the systematic uncertainty on the missing transverse momentum scale is presented.
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 2012
Measurements of the electron and muon inclusive cross-sections in proton-proton collisions at √ s... more Measurements of the electron and muon inclusive cross-sections in proton-proton collisions at √ s = 7 TeV with the ATLAS detector ✩ .ATLAS Collaboration a r t i c l e i n f o a b s t r a c t
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 2012
A measurement of the production cross-section for top quark pairs (tt) in pp collisions at √ s = ... more A measurement of the production cross-section for top quark pairs (tt) 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 two different topologies: single lepton (electron e or muon µ) with large missing transverse energy and at least four jets, and dilepton (ee, µµ or eµ) with large missing transverse energy and at least two jets. In a data sample of 2.9 pb −1 , 37 candidate events are observed in the single-lepton topology and 9 events in the dilepton topology. The corresponding expected backgrounds from non-tt Standard Model processes are estimated using data-driven methods and determined to be 12.2 ± 3.9 events and 2.5 ± 0.6 events, respectively. The kinematic properties of the selected events are consistent with SM tt production. The inclusive top quark pair production cross-section is measured to be
European Physical Journal C, 2012
The top quark mass has been measured using the template method in the tt → lepton + jets channel ... more The top quark mass has been measured using the template method in the tt → lepton + jets channel based on data recorded in 2011 with the ATLAS detector at the LHC. The data were taken at a proton-proton centre-of-mass energy of √ s = 7 TeV and correspond to an integrated luminosity of 1.04 fb −1 . The analyses in the e + jets and μ + jets decay channels yield consistent results. The top quark mass is measured to be m top = 174.5 ± 0.6 stat ± 2.3 syst GeV.
Physical Review D - Particles, Fields, Gravitation and Cosmology, 2012
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Papers by R. Asfandiyarov