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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 1,765 records · Page 98
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DOE OSTI2012

Forward-backward correlations and charged-particle azimuthal distributions in pp interactions using the ATLAS detector

CERN-LHC. Using inelastic proton-proton interactions at sqrt(s) = 900 GeV and 7 TeV, recorded by the ATLAS detector at the LHC, measurements have been made of the correlations between forward and backward charged-particle multiplicities and, for the first time, between forward and backward charged-particle summed transverse momentum. In addition, jet-like structure in the events is studied by means of azimuthal distributions of charged particles relative to the charged particle with highest transverse momentum in a selected kinematic region of the event. The results are compared with predictions from tunes of the PYTHIA and HERWIG++ Monte Carlo generators, which in most cases are found to provide a reasonable description of the data. Data taken from the RIVET analysis code.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Measurement of the b-hadron production cross section using decays to D ∗ μ − X final states in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector

CERN-LHC. The b-hadron production cross section is measured with the ATLAS detector in pp collisions at sqrt(s) = 7 TeV, using 3.3 pb^-1 of integrated luminosity, collected during the 2010 LHC run. The b-hadrons are selected by partially reconstructing D*muX final states. Differential cross sections are measured as functions of the transverse momentum and pseudorapidity. The measured production cross section for a b-hadron with pT>9 GeV and |eta|<2.5 is 32.7 pm 0.8 (stat) ^{+4.5}_{-6.8} (syst) ub, higher than the next-to-leading-order QCD predictions but consistent within the experimental and theoretical uncertainties. Data taken from the RIVET analysis code.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Measurements of the pseudorapidity dependence of the total transverse energy in proton-proton collisions at s = 7 TeV with ATLAS

CERN-LHC. This paper describes measurements of the sum of the transverse energy of particles as a function of particle pseudorapidity, eta, in proton-proton collisions at a centre-of-mass energy, sqrt(s) = 7 TeV using the ATLAS detector at the Large Hadron Collider. The measurements are performed in the region |eta| < 4.8 for two event classes: those requiring the presence of particles with a low transverse momentum and those requiring particles with a significant transverse momentum. In the second dataset measurements are made in the region transverse to the hard scatter. The distributions are compared to the predictions of various Monte Carlo event generators, which generally tend to underestimate the amount of transverse energy at high |eta|. Data taken from the RIVET analysis code.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Measurement of the flavour composition of dijet events in p p collisions at s = 7 TeV with the ATLAS detector

CERN-LHC. This paper describes a measurement of the flavour composition of dijet events produced in pp collisions at sqrt{s}=7 TeV using the ATLAS detector. The measurement uses the full 2010 data sample, corresponding to an integrated luminosity of 39 pb^-1. Six possible combinations of light, charm and bottom jets are identified in the dijet events, where the jet flavour is defined by the presence of bottom, charm or solely light flavour hadrons in the jet. Kinematic variables, based on the properties of displaced decay vertices and optimised for jet flavour identification, are used in a multidimensional template fit to measure the fractions of these dijet flavour states as functions of the leading jet transverse momentum in the range 40 GeV to 500 GeV and jet rapidity |y| < 2.1. The fit results agree with the predictions of leading- and next-to-leading-order calculations, with the exception of the dijet fraction composed of bottom and light flavour jets, which is underestimated by all models at large transverse jet momenta. The ability to identify jets containing two b-hadrons, originating from e.g. gluon splitting, is demonstrated. The difference between bottom jet production rates in leading and subleading jets is consistent with the next-to-leading-order predictions. Data taken from the RIVET analysis code.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Search for New Phenomena in Dijet Angular Distributions in Proton-Proton Collisions at s = 8 TeV Measured with the ATLAS Detector

CERN-LHC. A search for new phenomena in LHC proton-proton collisions at a center-of-mass energy of sqrt(s)= 8 TeV was performed with the ATLAS detector using an integrated luminosity of 17.3 fb^{-1}. The angular distributions are studied in events with at least two jets; the highest dijet mass observed is 5.5 TeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Search for massive, long-lived particles using multitrack displaced vertices or displaced lepton pairs in pp collisions at s = 8 TeV with the ATLAS detector

CERN-LHC. Many extensions of the Standard Model posit the existence of heavy particles with long lifetimes. This article presents the results of a search for events containing at least one long-lived particle that decays at a significant distance from its production point into two leptons or into five or more charged particles.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Measurement of transverse energy-energy correlations in multi-jet events in p p collisions at s = 7 TeV using the ATLAS detector and determination of the strong coupling constant &#x3B1; s ( m Z )

CERN-LHC. High transverse momentum jets produced in pp collisions at a centre of mass energy of 7 TeV are used to measure the transverse energy-energy correlation function and its associated azimuthal asymmetry. The data were recorded with the ATLAS detector at the LHC in the year 2011 and correspond to an integrated luminosity of 158 /pb. The selection criteria demand the average transverse momentum of the two leading anti-kT r=0.4 jets in an event to be larger than 250 GeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Measurement of the inclusive jet cross-section in proton-proton collisions at s = 7 TeV using 4.5 fb &#x2212; 1 of data with the ATLAS detector

CERN-LHC. Double-differential inclusive jet cross-sections measured in pp collisions at the LHC with a 7 TeV centre-of-mass energy are presented as functions of jet transverse momentum and absolute value of rapidity. These measurements are obtained using data corresponding to an integrated luminosity of 4.5 fb^-1, recorded by the ATLAS detector in 2011. The data are corrected for detector effects so that cross-sections are presented at the particle level. Cross-sections are measured up to jet transverse momentum of 2 TeV using jets reconstructed with the anti-kt algorithm with the jet radius parameter R = 0.4 and 0.6.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Search for dark matter in events with heavy quarks and missing transverse momentum in p p collisions with the ATLAS detector

CERN-LHC. This article reports on a search for dark matter pair production in association with bottom or top quarks in 20.3 fb 8 of pp collisions collected at sqrt(s) = 8 TeV by the ATLAS detector at the LHC. Events with large missing transverse momentum are selected when produced in association with high-momentum jets of which one or more are identified as jets containing b -quarks. Final states with top quarks are selected by requiring a high jet multiplicity and in some cases a single lepton. The data are found to be consistent with the Standard Model expectations and limits are set on the mass scale of effective field theories that describe scalar and tensor interactions between dark matter and Standard Model particles. Limits on the dark-matter=8 TeV by the ATLAS detector at the LHC. Events with large missing transverse momentum are selected when produced in association with high-momentum jets of which one or more are identified as jets containing b-quarks. Final states with top quarks are selected by requiring a high jet multiplicity and in some cases a single lepton. The data are found to be consistent with the Standard Model expectations and limits are set on the mass scale of effective field theories that describe scalar and tensor interactions between dark matter and Standard Model particles. Limits on the dark-matter--nucleon cross-section for spin-independent and spin-dependent interactions are also provided. These limits are particularly strong for low-mass dark matter. Using a simplified model, constraints are set on the mass of dark matter and of a coloured mediator suitable to explain a possible signal of annihilating dark matter.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Measurement of distributions sensitive to the underlying event in inclusive Z-boson production in p p collisions at s = 7 TeV with the ATLAS detector

CERN-LHC. A measurement of charged-particle distributions sensitive to the properties of the underlying event is presented for an inclusive sample of events containing a Z-boson, decaying to an electron or muon pair. The measurement is based on data collected using the ATLAS detector at the LHC in proton--proton collisions at a centre-of-mass energy of 7 TeV with an integrated luminosity of 4.6/fb.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Dijet production in s = 7 TeV p p collisions with large rapidity gaps at the ATLAS experiment

CERN-LHC. Measurements of the pseudorapidity gap and xi distributions for dijet production in diffractive events which are defined by large gaps devoid of activity seen in the ATLAS detector, based on a sample of proton-proton collisions at a centre-of-mass energy of 7 TeV of integrated luminosity of 6.8 nb-1 collected in 2010. The final state consists of two jets found by the anti-kt jet algorithm with transverse momentum greater than 20 GeV and empty regions in the acceptance of the ATLAS detector. The pseudorapidity gap variable, denoted here as DELTA(C=RAPGAP), is defined as the larger of the pseudorapidity regions extending to the limits of the ATLAS detector sensitivity at eta=+-4.8, in which no final state particles are observed above a (transverse) momentum threshold. The xi variable is calculated using M**2/S and for Single Diffraction DELTA(C=RAPGAP)~=-ln(xi). See PLBXX (2015) YY for more details.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Measurement of jet charge in dijet events from sqrt(s)=8 TeV pp collisions with the ATLAS detector

CERN-LHC. Measurements of the jet charge in dijet events in proton-proton collisions at a centre-of-mass energy of 8 TeV with 20.3 fb^-1 of data collected in 2012. The jet charge is a momentum-weighted sum of charges of tracks associated to the jet. The momentum is regulated by an exponent kappa. Measurements are reported for the average and standard deviation of the jet charge distribution as a function of the magnitude of the jet transverse momentum for kappa = 0.3, 0.5, 0.7 and separately for the more forward and more central jets (in pseudo-rapidity). The event selection is minimal, with only a requirement that the magnitude of the transverse momenta of the two leading jets be above 50 GeV and that these momenta be within 50% of each other.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗