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Bathe, S.

Publications and source records attributed to Bathe, S..

84 records · Page 5
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DOE OSTI2015

Charged-pion cross sections and double-helicity asymmetries in polarized p + p collisions at s = 200 GeV

In this paper, we present midrapidity charged-pion invariant cross sections, the ratio of the π - to π + cross sections and the charge-separated double-spin asymmetries in polarized p+p collisions at s = 200 GeV . While the cross section measurements are consistent within the errors of next-to-leading-order (NLO) perturbative quantum chromodynamics predictions (pQCD), the same calculations overestimate the ratio of the charged-pion cross sections. This discrepancy arises from the cancellation of the substantial systematic errors associated with the NLO-pQCD predictions in the ratio and highlights the constraints these data will place on flavor-dependent pion fragmentation functions. Lastly, the charge-separated pion asymmetries presented here sample an x range of ~0.03–0.16 and provide unique information on the sign of the gluon-helicity distribution.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Cross section for b b ¯ production via dielectrons in d + Au collisions at s N N = 200 GeV

We report a measurement of e⁺e⁻ pairs from semileptonic heavy-flavor decays in d+Au collisions at √s NN = 200 GeV. Thus, exploring the mass and transverse-momentum dependence of the yield, the bottom decay contribution can be isolated from charm, and quantified by comparison to PYTHIA and MC@NLO simulations. The resulting bb-production cross section is σ d Au bb =1.37±0.28(stat)±0.46(syst) mb, which is equivalent to a nucleon-nucleon cross section of σ NN bb =3.4 ± 0.8(stat)±1.1(syst) µb.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Nuclear matter effects on J/ψ production in asymmetric Cu + Au collisions at \(\sqrt{s_{\mathrm{NN}}} = 200\) GeV

We report on J/ψ production from asymmetric Cu+Au heavy-ion collisions at \(\sqrt{s_{\mathrm{NN}}} = 200\) GeV at the Relativistic Heavy Ion Collider at both forward (Cu-going direction) and backward (Au-going direction) rapidities. The nuclear modification of J/ψ yields in Cu+Au collisions in the Au-going direction is found to be comparable to that in Au+Au collisions when plotted as a function of the number of participating nucleons. In the Cu-going direction, J/ψ production shows a stronger suppression. This difference is comparable in magnitude and has the same sign as the difference expected from shadowing effects due to stronger low-x gluon suppression in the larger Au nucleus. Thus, the relative suppression is opposite to that expected from hot nuclear matter dissociation, since a higher energy density is expected in the Au-going direction.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2014

Cross section and transverse single-spin asymmetry of eta mesons in p ↑ plus p collisions at √s=200 GeV at forward rapidity

We present a measurement of the cross section and transverse single-spin asymmetry (A N ) for η mesons at large pseudorapidity from √s=200 GeV p ↑ +p collisions. The measured cross section for 0.5 T <5.0 GeV/c and 3.0<|η|<3.8 is well described by a next-to-leading-order perturbative-quantum-chromodynamics calculation. The asymmetries A N have been measured as a function of Feynman-x (x F ) from 0.2<|x F |<0.7, as well as transverse momentum (p T ) from 1.0 T <4.5 GeV/c. The asymmetry averaged over positive x F is (A N ) = 0.061±0.014. The results are consistent with prior transverse single-spin measurements of forward η and π⁰ mesons at various energies in overlapping x F ranges. Comparison of different particle species can help to determine the origin of the large observed asymmetries in p ↑ +p collisions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

PHENIX highlights

Results from RHIC led to the discovery of the strongly coupled quark–gluon plasma (sQGP), a state of the QCD vacuum. In order to arrive at a coherent picture of this state, both the properties of the sQGP and the conditions under which the sQGP is measured have to be established. In this paper, we present recent experimental results of the PHENIX Collaboration, further constraining the conditions and the properties of the sQGP at RHIC: measurement of direct photon elliptic flow provides strong constraints for hydrodynamic models employed to derive the initial temperature; measurement of v 2 and v 3 disentangles effects from the initial state and η/s; flow and R AA measurements at lower $\sqrt{s}$ extend the results to a regime at lower temperature and higher baryon density.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗