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Archambault, J. P.

Publications and source records attributed to Archambault, J. P..

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

Measurement of the charge asymmetry in top quark pair production in pp collisions at $\sqrt{s}=7\ \mathrm{TeV}$ using the ATLAS detector

A measurement of the top-antitop production charge asymmetry A C is presented using data corresponding to an integrated luminosity of 1.04 fb -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 tt event topology. After background subtraction, a Bayesian unfolding procedure is performed to correct for acceptance and detector effects. The measured value of A C is A C =-0.019±0.028 (stat.)±0.024 (syst.), consistent with the prediction from the MC@NLO Monte Carlo generator of A C = 0.006±0.002. Measurements of A C in two ranges of invariant mass of the top-antitop pair are also shown.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Search for lepton flavour violation in the eμ continuum with the ATLAS detector in $\sqrt{s} = 7~\mbox{TeV}$ pp collisions at the LHC

This paper presents a search for the t-channel exchange of an R-parity violating scalar top quark ($\sim\atop{t}$) in the e ± μ ∓ continuum using 2.1 fb 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$_t^-$). 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$_t^-$ = 95 GeV to 30 fb for m$_t^-$ = 1000 GeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

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

A measurement of the production cross-section for top quark pairs ($t\bar{t}$) in pp collisions at $\sqrt{s} = 7TeV 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 -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 $t\bar{t}$ = 187±11 (stat.) $+18\atop{-17}$ (syst.) ± 6 (lumi.) pb and σ $t\bar{t}$ =173 ± 17 (stat.) $+18\atop{-16}$ (syst.) ± 6 (lumi.) pb respectively. In conclusion, the two measurements are in agreement with each other and with QCD calculations. The first measurement has a better a priori sensitivity and constitutes the main result of this Letter.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2012

Search for decays of stopped, long-lived particles from 7 TeV pp collisions with the ATLAS detector

New metastable massive particles with electric and colour charge are features of many theories beyond the Standard Model. A search is performed for long-lived gluino-based R-hadrons with the ATLAS detector at the LHC using a data sample corresponding to an integrated luminosity of 31 pb -1 . Here, we search for evidence of particles that have come to rest in the ATLAS detector and decay at some later time during the periods in the LHC bunch structure without proton–proton collisions. No significant deviations from the expected backgrounds are observed, and a cross-section limit is set. It can be interpreted as excluding gluino-based R-hadrons with masses less than 341 GeV at the 95 % C.L., for lifetimes from 10 -5 to 10 3 seconds and a neutralino mass of 100 GeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

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

A search for microscopic black holes has been performed in a same-sign dimuon final state using 1.3 fb{sup -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.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗