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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Search for non-resonant Higgs boson pair production in the $2b+2\ell +{E}_{\textrm{T}}^{\textrm{miss}}$ final state in pp collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector

A search for non-resonant Higgs boson pair (HH) production is presented, in which one of the Higgs bosons decays to a b-quark pair ($b\bar{b}$) and the other decays to WW * , ZZ * , or τ + τ – , with in each case a final state with ℓ + ℓ – + neutrinos (ℓ = e, μ). The analysis targets separately the gluon-gluon fusion and vector boson fusion production modes. Data recorded by the ATLAS detector in proton-proton collisions at a centre-of-mass energy of 13 TeV at the Large Hadron Collider, corresponding to an integrated luminosity of 140 fb –1 , are used in this analysis. Events are selected to have exactly two b-tagged jets and two leptons with opposite electric charge and missing transverse momentum in the final state. These events are classified using multivariate analysis algorithms to separate the HH events from other Standard Model processes. No evidence of the signal is found. The observed (expected) upper limit on the cross-section for non-resonant Higgs boson pair production is determined to be 9.7 (16.2) times the Standard Model prediction at 95% confidence level. The Higgs boson self-interaction coupling parameter κ λ and the quadrilinear coupling parameter κ 2V are each separately constrained by this analysis to be within the ranges [–6.2, 13.3] and [–0.17, 2.4], respectively, at 95% confidence level, when all other parameters are fixed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Measurement of the properties of Higgs boson production at $\sqrt{s}$ = 13 TeV in the H → γγ channel using 139 fb -1 of pp collision data with the ATLAS experiment

Measurements of Higgs boson production cross-sections are carried out in the diphoton decay channel using 139 fb -1 of pp collision data at $\sqrt{s}$ = 13 TeV collected by the ATLAS experiment at the LHC. The analysis is based on the definition of 101 distinct signal regions using machine-learning techniques. The inclusive Higgs boson signal strength in the diphoton channel is measured to be $1.04^{+0.10}_{-0.09}$. Cross-sections for gluon-gluon fusion, vector-boson fusion, associated production with a W or Z boson, and top associated production processes are reported. An upper limit of 10 times the Standard Model prediction is set for the associated production process of a Higgs boson with a single top quark, which has a unique sensitivity to the sign of the top quark Yukawa coupling. Higgs boson production is further characterized through measurements of Simplified Template Cross-Sections (STXS). In total, cross-sections of 28 STXS regions are measured. The measured STXS cross-sections are compatible with their Standard Model predictions, with a p-value of 93%. The measurements are also used to set constraints on Higgs boson coupling strengths, as well as on new interactions beyond the Standard Model in an effective field theory approach. No significant deviations from the Standard Model predictions are observed in these measurements, which provide significant sensitivity improvements compared to the previous ATLAS results.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Charmed matter

In the near future experiments will be able to produce charmed hadrons almost at rest in the interior of an atomic nucleus. One of the most exciting perspectives is the possibility of studying charmonium in a dense medium. In the present communication we present results of a study that explores the possibility that J/{Psi} might be bound in a large nucleus through the excitation of intermediate states of D and D* mesons. We also present results of a recent prediction for the production of {Lambda}(bar sign){sub c}{sup -{Lambda}}{sub c}{sup +} in proton-antiproton annihilation experiments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Partonic substructure of nucleons and nuclei with dimuon production

Dimuon production has been studied in a series of fixed-target experiments at Fermilab during the last two decades. Highlights from these experiments, together with recent results from the Fermilab E866 experiment, are presented. Future prospects for studying the parton distributions in the nucleons and nuclei using dimuon production are also discussed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Study of kaonic final states in {pi}{sup -} p at 190 GeV

We discuss the status of analyses of data recorded in the 2008 and 2009 runs of the COMPASS experiment at CERN with sepcific focus on final states with K{sub S}{sup 0}K{sub S}{sup 0{pi}}- and K{sup +}K{sup -{pi}-} produced in {pi}{sup -}(190 GeV)p scattering. The interest in such final states is motivated by a summary of some of the relevant literature. We also show first results from the analysis of diffractively produced KK-bar{pi} states. Two prominent three-body structures, one around 1.8 GeV, the other at 2.2 GeV decaying via known KK-bar and K{pi} states are seen.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Quarkonium production in association with a photon and nuclear effects

In this contribution we investigate the influence of nuclear effects in hadroproduction of quarkonium associated with a photon. At high energies, such processes provide a probe of the QCD dynamics as it is dependent on the nuclear gluon distribution, and could be usefull in constraining the behavior of the nuclear gluon distribution in proton-nucleus and nucleus-nucleus collisions. Here we study the influence of the shadowing effect, in the production of J/{Psi}+{gamma} at the LHC and estimate the pT dependence of the nuclear modification factors. The theoretical framework considered for J/{Psi}+{gamma} production is the non-relativistic QCD (NRQCD) factorization formalism.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Higgs production via gluon fusion in k{sub T} factorisation

Theoretical studies of Higgs production via gluon fusion are frequently carried out in the limit where the top quark mass is much larger than the Higgs mass, an approximation which reduces the top quark loop to an effective vertex. We present a numerical analysis of the error thus introduced by performing a Monte Carlo calculation for gg{yields}h in k{sub T}-factorisation, using the parton shower generator CASCADE. By examining both inclusive and exclusive quantities, we find that retaining the top-mass dependence results in only a small enhancement of the cross-section. We then proceed to compare CASCADE to the collinear Monte Carlos PYTHIA, MC-NLO and POWHEG.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Contribution of a pure NCG forbidden process to the Z associated Higgs production

The contribution of the pure NCG forbidden subprocess gg{yields}ZHis calculated. It is shown that the cross section becomes important at the LHC energies and depends strongly on the choice of the noncommutativity parameter. Because of the gluons luminosity inside the proton, it becomes comparable to that of the commutative standard model subprocess qq(bar sign)ZH for reasonable values of the NCG parameter.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

NCG gluon fusion for the Higgs production at large hadron colliders

A pure NCG gluon fusion contribution to the Higgs production at large hadron colliders is discussed. It is shown that the NCG results become relevant at very high energies. This can be a good signal for the space-time non commutativity events.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Polarization test of Higgs spin and parity

Photon polarization measurements provide a model independent determination of the spin and the parity of the Higgs resonance. The test described here is based on very general principles and is completely independent of dynamical assumptions. A set of observables are identified that discriminate resonances with J{sup P} = 0{sup +}, 0{sup −}, 2{sup −} and 2{sup +}. Furthermore, the same set can be used to gain useful and important information on the magnitude of each helicity amplitude contributing to the gg → γγ process.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Inclusive jet cross section and strong coupling constant measurements at CMS

The probes which are abundantly produced in high energetic proton-proton (pp) collisions at the LHC are called jets. Events with jets can be described by Quantum Chromodynamics (QCD) in terms of parton-parton scattering. The inclusive jet cross section in pp collision is the fundamental quantity which can be measured and predicted within the framework of perturbative QCD (pQCD). The strong coupling constant α{sub S} which can be determined empirically in the limit of massless quarks, is the single parameter in QCD. The jet measurements can also be used to determine strong coupling constant α{sub S} and parton density functions (PDFs). The recent jet measurements which are performed with the data collected by the CMS detector at different center-of-mass energies and down to very low transverse momentum p{sub T} are presented. The measurements are compared to Monte Carlo predictions and perturbative calculations up to next-to-next-to leading order. Finally, the precision jet measurements give further insight into the QCD dynamics.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Dirac dark matter with a charged mediator: a comprehensive one-loop analysis of the direct detection phenomenology

We analyze the direct detection signals of a toy model consisting of a Dirac dark matter particle which couples to one Standard Model fermion via a scalar mediator. For all scenarios, the dark matter particle scatters off nucleons via one loop-induced electromagnetic and electroweak moments, as well as via the one-loop exchange of a Higgs boson. Besides, and depending on the details of the model, the scattering can also be mediated at tree level via the exchange of the scalar mediator or at one loop via gluon-gluon interactions. We show that, for thermally produced dark matter particles, the current limits from the LUX experiment on these scenarios are remarkably strong, even for dark matter coupling only to leptons. We also discuss future prospects for XENON1T and DARWIN and we argue that multi-ton xenon detectors will be able to probe practically the whole parameter space of the model consistent with thermal production and perturbativity. We also discuss briefly the implications of our results for the dark matter interpretation of the Galactic GeV excess.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Pair production of color-octet scalars at the LHC

Heavy colored scalar particles, which exist in many models of new physics, can be pair produced at the LHC via gluon-gluon fusion and possibly form quarkoniumlike bound states. If the scalars are also charged under the electroweak gauge group, these bound states can then decay into electroweak bosons. This yields a resonant cross section for final states such as {gamma}{gamma} that can exceed standard model backgrounds. This paper studies this process in the Manohar-Wise model of color-octet scalars (COS). Important threshold logarithms and final state Coulomb-like QCD interactions are resummed using effective field theory. We compute the resummed cross section for gluon-gluon fusion to COS pairs at the LHC as well as the resonant cross section for octetonium decaying to {gamma}{gamma}. The latter cross section exceeds the standard model diphoton cross section when the COS mass is less than 500 (350) GeV for {radical}(s)=14(7) TeV. Nonobservation of resonances below these energies can significantly improve existing bounds on COS masses.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Edge charge asymmetry in top pair production at the LHC

In this brief report, we propose a new definition of charge asymmetry in top pair production at the LHC, namely, the edge charge asymmetry (ECA). ECA utilizes the information of drifting direction only for single top (or antitop) with hadronic decay. Therefore, ECA can be free from the uncertainty arising from the missing neutrino in the tt event reconstruction. Moreover, rapidity Y of top (or antitop) is required to be greater than a critical value Y{sub C} in order to suppress the symmetric tt events mainly due to the gluon-gluon fusion process. In this paper, ECA is calculated up to next-to-leading order QCD in the standard model and the choice of the optimal Y{sub C} is investigated.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Cross section and transverse single-spin asymmetry of muons from open heavy-flavor decays in polarized p + p collisions at s = 200 ? ? GeV

The cross section and transverse single-spin asymmetries of μ - and μ + from open heavy-flavor decays in polarized p+p collisions at √s = 200 GeV were measured in this paper by the PHENIX experiment during 2012 at the Relativistic Heavy Ion Collider. Because heavy-flavor production is dominated by gluon-gluon interactions at √s = 200 GeV, these measurements offer a unique opportunity to obtain information on the trigluon correlation functions. The measurements are performed at forward and backward rapidity (1.4 < |y| < 2.0) over the transverse momentum range of 1.25 < p T < 7 GeV/c for the cross section and 1.25 < p T < 5 GeV/c for the asymmetry measurements. The obtained cross section is compared to a fixed-order-plus-next-to-leading-log perturbative-quantum-chromodynamics calculation. Finally, the asymmetry results are consistent with zero within uncertainties, and a model calculation based on twist-3 three-gluon correlations agrees with the data.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Search for Dijet Resonances in 7 TeV pp Collisions at CMS

A search for narrow resonances in the dijet mass spectrum is performed using data corresponding to an integrated luminosity of 2.9 inverse pb collected by the CMS experiment at the LHC. Upper limits at the 95% confidence level (CL) are presented on the product of the resonance cross section, branching fraction into dijets, and acceptance, separately for decays into quark-quark, quark-gluon, or gluon-gluon pairs. The data exclude new particles predicted in the following models at the 95% CL: string resonances, with mass less than 2.50 TeV, excited quarks, with mass less than 1.58 TeV, and axigluons, colorons, and E_6 diquarks, in specific mass intervals. This extends previously published limits on these models.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Evidence for Simultaneous Production of J/ψ and Υ Mesons

We report evidence for the simultaneous production of J/ψ and Υ mesons in 8.1 fb$^{-1}$of data collected at $\sqrt{s}$ = 1.96 TeV by the D0 experiment at the Fermilab $p\bar{p}$ Tevatron Collider. Events with these characteristics are expected to be produced predominantly by gluon-gluon interactions. In this analysis, we extract the effective cross section characterizing the initial parton spatial distribution, σ$_{eff}$=2.2±0.7(stat)±0.9(syst) mb.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗