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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Vector-boson-tagged jet production in heavy ion collisions at energies available at the CERN Large Hadron Collider [Vector boson-tagged jet production in heavy ion collisions at the LHC]

Here, vector-boson-tagged jet production in collisions of heavy nuclei opens new opportunities to study parton shower formation and propagation in strongly interacting matter. It has been argued to provide a golden channel that can constrain the energy loss of jets in the quark-gluon plasma created in heavy ion reactions. We present theoretical results for isolated-photon-tagged and Z 0 -boson-tagged jet production in Pb + Pb collisions with √s NN = 5.02TeV at the LHC. Specifically, we evaluate the transverse momentum imbalance x JV distribution and nuclear modification factor I AA of tagged jets and compare our theoretical calculations to recent experimental measurements by ATLAS and CMS collaborations. Our analysis, which includes both collisional and radiative energy losses, sheds light on their relative importance versus the strength of jet-medium interactions and helps quantify the amount of out-of-cone radiation of predominantly prompt quark-initiated jets.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

Same-sign Higgsino production at the CERN LHC: How not to hunt for natural supersymmetry

We examine the prospects for detecting light charged higgsinos that are expected to be a necessary feature of natural SUSY models via pp→$\widetilde{W}$$±\atop{1}$$\widetilde{W}$$±\atop{1}$jj+X processes arising dominantly from W ± W ± fusion at LHC13. The signal will be a pair of same-sign leptons (e or μ) in events with two relatively forward, hemispherically-separated jets with a large rapidity gap. We find that even though the higgsinos have a full-strength SU(2) gauge couplings to W-bosons, the LHC13 cross section for the production of same sign higgsino pairs is smaller than 0.02 fb over most of the interesting range of natural SUSY parameters, even before leptonic branching fractions of the chargino are included. This cross section is strongly suppressed because the two neutral Majorana higgsinos can be combined into a single Dirac neutralino if the bino and the winos are much heavier than the higgsinos, as is the case in natural SUSY models: in this limit, higgsino couplings to W-bosons exhibit an emergent (approximate) U(1) ino global symmetry that suppresses same sign higgsino production by vector boson fusion. We conclude that this channel is not a viable way to search for natural SUSY even at the high luminosity upgrade of the Large Hadron Collider.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

New CHOD detector for the NA62 experiment at CERN

The New CHOD is a scintillation hodoscope with a pad structure featuring a total of 148 counters. The signal from each pad is read out using wavelength-shifting fibers and two or four SensL SiPMs with a sensitive area of 3 × 3 mm{sup 2}. This photodetector has 4774 pixels 35 × 35 μm{sup 2} in size. The key parameters (photon detection efficiency, dark current, crosstalk, and gain) were measured for 500 SiPMs.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Measurements of multiplicity fluctuations of identified hadrons in inelastic proton–proton interactions at the CERN Super Proton Synchrotron

Measurements of multiplicity fluctuations of identified hadrons produced in inelastic p+p interactions at 31, 40, 80, and 158 $\text {Ge}\text {V}/c$ beam momentum are presented. Three different measures of multiplicity fluctuations are used: the scaled variance $\omega $ and strongly intensive measures $\Sigma $ and $\Delta $. These fluctuation measures involve second and first moments of joint multiplicity distributions. Data analysis is preformed using the Identity method which corrects for incomplete particle identification. Strongly intensive quantities are calculated in order to allow for a direct comparison to corresponding results on nucleus–nucleus collisions. The results for different hadron types are shown as a function of collision energy. A comparison with predictions of string-resonance Monte-Carlo models: Epos, Smash and Venus, is also presented.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Impact of beam–beam effects on absolute luminosity calibrations at the CERN Large Hadron Collider

At the Large Hadron Collider (LHC), absolute luminosity calibrations obtained by the van der Meer (vdM) method are affected by the mutual electromagnetic interaction of the two beams. The colliding bunches experience relative orbit shifts, as well as optical distortions akin to the dynamic-β effect, that both depend on the transverse beam separation and must therefore be corrected for when deriving the absolute luminosity scale. In the vdM regime, the beam–beam parameter is small enough that the orbit shift can be calculated analytically. The dynamic-β corrections to the luminometer calibrations, however, had until the end of Run 2 been estimated in the linear approximation only. In this report, the influence of beam–beam effects on the vdM-based luminosity scale is quantified, together with the associated systematic uncertainties, by means of simulations that fully take into account the non-linearity of the beam–beam force, as well as the resulting non-Gaussian distortions of the transverse beam distributions. Two independent multiparticle simulations, one limited to the weak-strong approximation and one that models strong-strong effects in a self-consistent manner, are found in excellent agreement; both predict a percent-level shift of the absolute pp-luminosity values with respect to those assumed until recently in the physics publications of the LHC experiments. These results also provide guidance regarding further studies aimed at reducing the beam–beam-related systematic uncertainty on beam–beam corrections to absolute luminosity calibrations by the van der Meer method.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Performance of b Jet Identification at $\sqrt{s}$ = 13 TeV with the ATLAS Detector at CERN [Slides]

The efficient identification of jets from bottom quarks (b-jets) is one of the most important techniques for many physics analyses at the Large Hadron Collider, including studies of the Higgs boson, the top quark, and searches beyond the Standard Model. The performance is characterized by b-tagging efficiency (probability to identify a b-jet as such) and the mistag rate (probability to mistakenly accept a non-b-jet).The mistag occurs as a result of finite detector resolution, presence of long-lived particles, and material interactions. As these effects can be different between the experimental data and Monte Carlo (MC) simulation, it is important to measure the b-tagging performance in data and derive the MC correction factors. I will describe various methods to measure the performance of b jet identification in pp collisions at √s = 13 TeV with the ATLAS detector and will report on Direct Tag method which is recently developed in the ATLAS collaboration for Light jet calibration.

43 PARTICLE ACCELERATORS↗
DOE OSTI2019

Status of single phase and dual phase DUNE prototype detectors at CERN

DUNE is a next-generation long-baseline neutrino oscillation experiment designed to measure the neutrino mass hierarchy and CP-violation in the lepton sector. ProtoDUNE-SP and ProtoDUNE-DP are prototype detectors for the DUNE experiment, testing the single-phase and dual-phase liquid argon time projection chamber technologies, respectively. The detectors represent a key step towards realising the full 10 kt liquid argon time projection chamber detector modules that will form the far detector of DUNE. The status of the two ProtoDUNE detectors and the future timescales of the experiments are discussed.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗