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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,099 records · Page 61
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DOE OSTI2012

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

Data from a search for the production of SUSY particles in proton-proton interactions at a centre of mass of 7 TeV using final states contianing jets, missing transverse momentum and at least one hadronically decaying tau lepton. The data, collected between March and April 2011, has a total integrated luminosity of 2.05 +- 0.08 fb-1. The trigger required at least one jet with PT > 75 GeV and missing PT > 45 GeV. As well as the numerical values of the plots in the paper, this record lists the acceptances, efficiences, and other signal data.

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DOE OSTI2012

Measurement of charged-particle event shape variables in s = 7 TeV proton-proton interactions with the ATLAS detector

CERN-LHC. Measurements of the event shape variables Transverse Thrust, Transverse Thrust Minor and Transverse Sphericity in proton-proton collisions at a centre-of-mass energy of 7 TeV. Events with at least six final state charged particles are selected from a data sample collected in April 2010 with a minimum prescale factor for the minimum-bias trigger. In addition to the event shape distributions, data on the evolution of their mean values with charged particle multiplicity and scalar PT sum are presented.

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DOE OSTI2012

Search for light scalar top quark pair production in final states with two leptons with the ATLAS detector in s = 7 TeV proton-proton collisions

CERN-LHC. Study of events with final states comprising two opposite charge leptons, large missing transverse momentum and at least one jet in proton proton collisions at a centre-of-mass energy of 7 TeV. Uses the full 2011 data sample of 4.7fb-1. Data is given for the distributions of leading PT of the leptons and jets and of Missing ET for E-E, E-MU and MU-MU final states.

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DOE OSTI2012

Hunt for new phenomena using large jet multiplicities and missing transverse momentum with ATLAS in 4.7 fb − 1 of s = 7 TeV proton-proton collisions

CERN-LHC. Study of final states from proton-proton interactions at a centre-of-mass energy of 7 TeV having >=6 to >=9 jets in association with missing transverse momentum and no isolated electrons or muons. The data sample, collected in 2011, has a total integrated luminsoity of 4.7 pb-1. The results are interpretated in the context of a MSUGRA/CMSSM SUSY model and also a simplified model containing only a gluino octet and a neutralino. Distributions of Missing-ET/sqrt(HT), where HT is the scalar sum of the transverse momentum of the jets, are given here for 6 signal regions from minimum 6 to 9 jets with minimum PT > 55 and 80 GeV. Tables of acceptances, efficiencies, errors and CLs value for each signal region for both SUSY models are also provided in the link below.

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DOE OSTI2012

Measurement of W Z production in proton-proton collisions at s = 7 TeV with the ATLAS detector

CERN-LHC. Measurements of the cross section for W+- plus Z0 production in proton proton collisions at a centre-of mass energy of 7 TeV. The data sample used, collected during 2011, has a total integrated luminosity of 4.6 fb-1 with 317 candidate events in the double leptonic decay final state with electrons, muons and missing transverse momentum. The total cross section is presented together with fiducial cross sections in a common phase space region.

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DOE OSTI2012

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

CERN-LHC. Study of events with final states containing charged hadrons and an associated muon produced in proton-proton collisions at a centre-of-mass energy of 7 TeV. The data sample, collected in 2011, has an integrated luminosity of 4.4 fb-1. The data are interpreted in the context of R-parity violating supersymmetric scenarios in a search for heavy particles with long lifetimes decaying into these final states.

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DOE OSTI2012

Search for Supersymmetry in Events with Large Missing Transverse Momentum, Jets, and at Least One Tau Lepton in 7 TeV Proton-Proton Collision Data with the ATLAS Detector

CERN-LHC. Study of events from proton-proton interactions at a centre-of-mass energy of 7 Tev which have final states comprising large missing transverse momentum, jets and at least one hadronically decaying TAU letpton accompanied by zero or one additional light lepton (ELECTRON or MUON). The data sample, collected during 2011, has an integrated luminosity of 4.7 fb-1. In the framework of gauge-mediated SUSY-breaking (GMSB) models, lower limits on the mass scale LAMBDA are determined. Data are presented for four channels comprising single and double TAU production with no extra light leptons and single TAU production with an ELECTRON and with a MUON. The exclusion data are from the combined channels. Acceptances and efficiencies for each channel are tabulated.

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DOE OSTI2012

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

CERN-LHC. Study of events from proton-proton interactions at a centre-of-mass energy of 7 TeV which have final states comprising exclusively one or two leptons (either electrons or muons), large missing transverse momentum, light flavour jets and b-jets. The data sample used has an integrated luminosity of 4.7 fb-1. The data are analysed in the framework of MSSM assuming the top squark decays exclusively to a chargino and b-quark. The data is divided into three signal regions, one (1LSR) requiring only one lepton with two light-quark jets and 2 b-jets, and two (2LSR1 and 2LSR2) requiring only two leptons and two leading jets with different requirements on the minimum energy and invariant mass of the specific subsystem from the hard-scattering process. The reader is refered to the text of the paper for more details.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Search for nonpointing photons in the diphoton and E T m i s s final state in s =7 TeV proton-proton collisions using the ATLAS detector

CERN-LHC. Study of events with a final state comprising two photons and missing transverse energy in proton-proton interactions at a centre-of-mass energy of 7 TeV using a data sample, collected in 2011, with an integrated luminosity of 4.8 fb-1. The analysis is focussed on a search for photons originating in the decay of neutral long-lived particles, exploiting the electromagnetic calorimeters ability to make measurements of the flight direction of the photons as well as excellent time resolution. Results are compared with Standard Model (SM ) expections as well as the predictions from GMSB models.

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DOE OSTI2013

Search for new phenomena in photon+jet events collected in proton--proton collisions at sqrt(s) = 8 TeV with the ATLAS detector

CERN-LHC. A model-independent search is made for the production of new resonances in photon + jet events using 20 fb^-1 of proton-proton LHC data recorded with the ATLAS detector in 2012 at a centre-of-mass energy of sqrt(s) = 8 TeV. The photon + jet mass distribution is compared to a background model fit from data; no significant deviation from the background-only hypothesis is found. Limits are set at 95% credibility level on generic Gaussian-shaped signals and two benchmark phenomena beyond the Standard Model: non-thermal quantum black holes and excited quarks. Non-thermal quantum black holes are excluded below masses of 4.6 TeV and excited quarks are excluded below masses of 3.5 TeV.

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DOE OSTI2014

Measurement of the cross section of high transverse momentum Z → b b ¯ production in proton--proton collisions at s = 8 T e V with the ATLAS Detector

CERN-LHC. This Letter reports the observation of a high transverse momentum Z0 --> BOTTOM BOTTOMBAR signal in proton-proton collisions at sqrt(s) = 8 TeV and 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 Z0 --> BOTTOM BOTTOMBAR decay is reconstructed from a pair of b-tagged jets, clustered with the anti-kt jet algorithm with R = 0.4, that have low angular separation and form a dijet with PT > 200 GeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Search for direct pair production of the top squark in all-hadronic final states in proton-proton collisions at s = 8 TeV with the ATLAS detector

CERN-LHC. The results of a search for direct pair production of the scalar partner to the top quark using an integrated luminosity of 20.1 fb^{-1} of proton-proton collision data at sqrt(s) = 8 TeV recorded with the ATLAS detector at the LHC are reported. The top squark is assumed to decay via stop --> t chi1^0 or stop --> b chi1^{+/-} --> b W^{(*)} chi1^0, where chi1^0 (chi1^{+/-}) denotes the lightest neutralino (chargino) in supersymmetric models. The search targets a fully-hadronic final state in events with four or more jets and large missing transverse momentum. No significant excess over the Standard Model background prediction is observed, and exclusion limits are reported in terms of the top squark and neutralino masses and as a function of the branching fraction of stop --> t chi1^0. For a branching fraction of 100%, top squark masses in the range 270-645 GeV are excluded for chi1^0 masses below 30 GeV. For a branching fraction of 50% to either stop --> t chi1^0 or stop --> b chi1^{+/-}, and assuming the chi1^{+/-} mass to be twice the chi1^0 mass, top squark masses in the range 250-550 GeV are excluded for chi1^0 masses below 60 GeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Search for squarks and gluinos with the ATLAS detector in final states with jets and missing transverse momentum using s = 8 TeV proton--proton collision data

CERN-LHC. A search for squarks and gluinos in final states containing high-pT jets, missing transverse momentum and no electrons or muons is presented. The data were recorded in 2012 by the ATLAS experiment in sqrt(s) = 8 TeV proton-proton collisions at the Large Hadron Collider, with a total integrated luminosity of 20.3 fb^{-1}. No significant excess above the Standard Model expectation is observed. Results are interpreted in a variety of simplified and specific supersymmetry-breaking models assuming that R-parity is conserved and that the lightest neutralino is the lightest supersymmetric particle. An exclusion limit at the 95% confidence level on the mass of the gluino is set at 1330 GeV for a simplified model incorporating only a gluino and the lightest neutralino. For a simplified model involving the strong production of first- and second-generation squarks, squark masses below 850 GeV (440 GeV) are excluded for a massless lightest neutralino, assuming mass degenerate (single light-flavour) squarks. In mSUGRA/CMSSM models with tan(beta) = 30, A0 = -2m0 and mu> 0, squarks and gluinos of equal mass are excluded for masses below 1700 GeV. Additional limits are set for non-universal Higgs mass models with gaugino mediation and for simplified models involving the pair production of gluinos, each decaying to a top squark and a top quark, with the top squark decaying to a charm quark and a neutralino. These limits extend the region of supersymmetric parameter space excluded by previous searches with the ATLAS detector.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Measurement of the underlying event in jet events from 7 TeV proton-proton collisions with the ATLAS detector

CERN-LHC. Distributions sensitive to the underlying event in QCD jet events have been measured with the ATLAS detector at the LHC, based on 37/pb of proton-proton collision data collected at a centre-of-mass energy of 7 TeV. Charged-particle mean pT and densities of all-particle ET and charged-particle multiplicity and pT have been measured in regions azimuthally transverse to the hardest jet in each event. These are presented both as one-dimensional distributions and with their mean values as functions of the leading-jet transverse momentum from 20 GeV to 800 GeV. The correlation of charged-particle mean pT with charged-particle multiplicity is also studied, and the ET densities include the forward rapidity region; these features provide extra data constraints for Monte Carlo modelling of colour reconnection and beam-remnant effects respectively. For the first time, underlying event observables have been computed separately for inclusive jet and exclusive dijet event selections, allowing more detailed study of the interplay of multiple partonic scattering and QCD radiation contributions to the underlying event. Comparisons to the predictions of different Monte Carlo models show a need for further model tuning, but the standard approach is found to generally reproduce the features of the underlying event in both types of event selection.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Search for strong production of supersymmetric particles in final states with missing transverse momentum and at least three b -jets at s = 8 TeV proton-proton collisions with the ATLAS detector

CERN-LHC. This paper reports the results of a search for strong production of supersymmetric particles in 20.1 fb-1 of proton-proton collisions at a centre-of-mass energy of 8 TeV using the ATLAS detector at the LHC. The search is performed separately in events with either zero or at least one high-pT lepton (electron or muon), large missing transverse momentum, high jet multiplicity and at least three jets identified as originated from the fragmentation of a b-quark. No excess is observed with respect to the Standard Model predictions. The results are interpreted in the context of several supersymmetric models involving gluinos and scalar top and bottom quarks, as well as a mSUGRA/CMSSM model. Gluino masses up to 1340 GeV are excluded, depending on the model, significantly extending the previous ATLAS limits.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Search for supersymmetry in events with large missing transverse momentum, jets, and at least one tau lepton in 20 fb − 1 of s = 8 TeV proton-proton collision data with the ATLAS detector

CERN-LHC. A search for supersymmetry (SUSY) in events with large missing transverse momentum, jets, at least one hadronically decaying tau lepton and zero or one additional light leptons (electron/muon), has been performed using 20.3 fb^-1 of proton-proton collision data at sqrt(s)=8 TeV recorded with the ATLAS detector at the Large Hadron Collider. No excess above the Standard Model background expectation is observed in the various signal regions and 95% confidence level upper limits on the visible cross section for new phenomena are set. The results of the analysis are interpreted in several SUSY scenarios, significantly extending previous limits obtained in the same final states. In the framework of minimal gauge-mediated SUSY breaking models, values of the SUSY breaking scale Lambda below 63 TeV are excluded, independently of tan(beta). Exclusion limits are also derived for an mSUGRA/CMSSM model, in both the R-parity-conserving and R-parity-violating case. A further interpretation is presented in a framework of natural gauge mediation, in which the gluino is assumed to be the only light coloured sparticle and gluino masses below 1090 GeV are excluded.

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