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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 1,477 records · Page 82
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DOE OSTI2015

Measurement of differential J / ψ production cross-sections and forward-backward ratio in p+Pb collisions with the ATLAS detector

CERN-LHC. Measurements of differential cross-sections for J/psi production in p+Pb collisions at sqrt(s_NN) = 5.02 TeV at the LHC with the ATLAS detector are presented. The data set used corresponds to an integrated luminosity of 28.1 nb^-1. The J/psi mesons are reconstructed in the dimuon decay channel over the transverse momentum range 8< pT< 30 GeV and over the center-of-mass rapidity range -2.87< y* <1.94. Prompt J/psi are separated from J/psi resulting from b-hadron decays through an analysis of the distance between the J/psi decay vertex and the event primary vertex. The differential cross-section for production of nonprompt J/psi is compared to a FONLL calculation that does not include nuclear effects. Forward-backward production ratios are presented and compared to theoretical predictions. These results constrain the kinematic dependence of nuclear modifications of charmonium and b-quark production in p+Pb collisions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Measurement of jet activity produced in top-quark events with an electron, a muon and two b -tagged jets in the final state in p p collisions at s = 13 TeV with the ATLAS detector

CERN-LHC, ATLAS. Measurement of jet activity in top-quark pair events produced in proton proton collisions at 13 TeV with 3.2fb-1 of data measured in 2015. Events are chosen by requiring an opposite-charge electron-muon pair and two b-tagged jets in the final state. Normalised differential cross sections are presented.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Search for new phenomena in a lepton plus high jet multiplicity final state with the ATLAS experiment using s = 13 Tev proton-proton collision data

CERN-LHC. A search for new phenomena in final states characterized by high jet multiplicity, an isolated lepton (electron or muon) and either zero or at least three b-tagged jets is presented. The search uses 36.1 fb-1 of sqrt(s) = 13 TeV proton-proton collision data collected by the ATLAS experiment at the Large Hadron Collider in 2015 and 2016. The dominant sources of background are estimated using parameterized extrapolations, based on observables at medium jet multiplicity, to predict the b-tagged jet multiplicity distribution at the higher jet multiplicities used in the search. No significant excess over the Standard Model expectation is observed and 95% confidence-level limits are extracted constraining four simplified models of R-parity-violating supersymmetry that feature either gluino or top-squark pair production. The exclusion limits reach as high as 2.1 TeV in gluino mass and 1.2 TeV in top-squark mass in the models considered. In addition, an upper limit is set on the cross-section for Standard Model tttt production of 60 fb (6.5 times the Standard Model prediction) at 95% confidence level. Finally, model-independent limits are set on the contribution from new phenomena to the signal-region yields.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Studies of Z &#x3B3; production in association with a high-mass dijet system in p p collisions at s = 8 TeV with the ATLAS detector

CERN-LHC. Measurements of the cross-section of the electroweak production in Zy final state in association with two jets, using two decay channels Z -> l+ l- and Z -> nu nu~ (with l=e,mu and nu=e/mu/tau neutrinos and nu~=e/mu/tau anti-neutrinos and y=photons) in proton-proton collision data corresponding to an integrated luminosity of 20.2 fb-1 at a centre of-mass energy of 8 TeV with the ATLAS detector at the Large Hadron Collider. Limits are also sets on WWZy/ZZZy/ZyZy/yyZy anomalous quartic gauge couplings.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Search for supersymmetry in final states with two same-sign or three leptons and jets using 36 fb &#x2212; 1 of s = 13 TeV p p collision data with the ATLAS detector

CERN-LHC. A search for strongly produced supersymmetric particles using signatures involving multiple energetic jets and either two isolated same-sign leptons (electrons or muons), or at least three isolated leptons, is presented. The analysis relies on b-tagged jets and missing transverse momentum, to achieve good sensitivity.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Search for Dark Matter Produced in Association with a Higgs Boson Decaying to b b &#xAF; using 36 fb &#x2212; 1 of p p collisions at s = 13 TeV with the ATLAS Detector

CERN-LHC. Several extensions of the Standard Model predict associated production of dark-matter particles with a Higgs boson. Such processes are searched for in final states with missing transverse momentum and a Higgs boson decaying to a bb pair with the ATLAS detector using 36.1 fb-1 of pp collisions at a center-of-mass energy of 13 TeV at the LHC. The observed data are in agreement with the Standard Model and limits are placed on the associated production of dark-matter particles and a Higgs boson.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Measurement of internal structure of jets in Pb+Pb collisions at s NN = 2.76 TeV with the ATLAS detector at the LHC

CERN-LHC. The distributions of transverse momentum and longitudinal momentum fraction of charged particles in jets are measured in Pb+Pb and pp collisions with the ATLAS detector at the LHC. The distributions are measured as a function of jet transverse momentum and rapidity. The analysis utilises an integrated luminosity of 0.14 nb^{-1} of Pb+Pb data and 4.0 pb^{-1} of pp data collected in 2011 and 2013, respectively, at the same centre-of-mass energy of 2.76 TeV per colliding nucleon pair. The distributions measured in pp collisions are used as a reference for those measured in Pb+Pb collisions in order to evaluate the impact on the internal structure of jets from the jet energy loss of fast partons propagating through the hot, dense medium created in heavy-ion collisions. Modest but significant centrality-dependent modifications of fragmentation functions in Pb+Pb collisions with respect to those in pp collisions are seen. No significant dependence of modifications on jet pt and rapidity selections is observed except for the fragments with the highest transverse momenta for which some reduction of yields is observed for more forward jets.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Measurement of W W / W Z &#x2192; &#x2113; &#x3BD; q q &#x2032; production with the hadronically decaying boson reconstructed as one or two jets in p p collisions at s = 8 TeV with ATLAS, and constraints on anomalous gauge couplings

CERN-LHC. This paper presents a study of the production of WW or WZ boson pairs, with one W boson decaying to electron-neutrino or muon-neutrino and one W or Z boson decaying hadronically. The analysis uses 20.2 fb-1 of sqrt(s)=8 TeV pp collision data, collected by the ATLAS detector at the Large Hadron Collider. Cross-sections for WW/WZ production are measured in high-pT fiducial regions defined close to the experimental event selection. The cross-section is measured for the case where the hadronically decaying boson is reconstructed as two resolved jets (WV->lvjj), and the case where it is reconstructed as a single jet (WV->lvJ). For the description of the WV->lvjj and WV->lvJ fiducial phase spaces, refer to section 8.1 and 8.2 of the paper. The transverse momentum distribution of the hadronically decaying boson is used to search for new physics. Observations are consistent with the Standard Model predictions, and 95% confidence intervals are calculated for parameters describing anomalous triple gauge-boson couplings (aTGCs). The aTGC search is done applying the same selection used for cross section measurement, plus an additional requirement for the jet-jet invariant mass (single jet mass) to be close to the W mass: 65 GeV < m_jj < 95 GeV (65 GeV < m_J < 95 GeV).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗