Search results for "Relativistic Heavy Ion Collider"
showing 8 items of 58 documents
Charged-pion cross sections and double-helicity asymmetries in polarizedp+pcollisions ats=200 GeV
2015
We present midrapidity charged-pion invariant cross sections, the ratio of the pi(-) to pi(+) cross sections and the charge-separated double-spin asymmetries in polarized p + p collisions at root s = p + 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. The char…
Recent results from PHENIX on the evolution of hot QCD
2014
The Relativistic Heavy Ion Collider’s (RHIC) energy scan program explores the phase transition between the hadron gas and the quark gluon plasma phases by varying center-of-mass energies from √sNN = 7.7 to 200 GeV and using various system sizes. The nuclear modification factor of π0 and the azimuthal anisotropy of charged hadrons were measured in Au+Au collisions at c.m. energies √sNN = 39, 62.4 and 200 GeV. In addition, we present recent results of direct photon yield and anisotropy measurements in Au+Au collisions at c.m. energy √sNN = 200 GeV.
Deviation from quark number scaling of the anisotropy parameterv2of pions, kaons, and protons inAu+Aucollisions atsNN=200GeV
2012
Measurements of the anisotropy parameter v(2) of identified hadrons (pions, kaons, and protons) as a function of centrality, transverse momentum p(T), and transverse kinetic energy KET at midrapidity (vertical bar eta vertical bar < 0.35) in Au + Au collisions at root s(N N) = 200 GeV are presented. Pions and protons are identified up to p(T) = 6 GeV/c, and kaons up to p(T) = 4 GeV/c, by combining information from time-of-flight and aerogel Cerenkov detectors in the PHENIX Experiment. The scaling of v(2) with the number of valence quarks (n(q)) has been studied in different centrality bins as a function of transverse momentum and transverse kinetic energy. A deviation from previously observ…
Cold-Nuclear-Matter Effects on Heavy-Quark Production ind+AuCollisions atsNN=200 GeV
2012
The PHENIX experiment has measured electrons and positrons at midrapidity from the decays of hadrons containing charm and bottom quarks produced in d+Au and p+p collisions at sqrt[S(NN)]=200 GeV in the transverse-momentum range 0.85 ≤ p(T)(e) ≤ 8.5 GeV/c. In central d+Au collisions, the nuclear modification factor R(dA) at 1.5<p(T)<5 GeV/c displays evidence of enhancement of these electrons, relative to those produced in p+p collisions, and shows that the mass-dependent Cronin enhancement observed at the Relativistic Heavy Ion Collider extends to the heavy D meson family. A comparison with the neutral-pion data suggests that the difference in cold-nuclear-matter effects on light- and heavy-…
Cross section and longitudinal single-spin asymmetry AL for forward W±→μ±ν production in polarized p+p collisions at s=510 GeV
2018
We have measured the cross section and single-spin asymmetries from forward W±→μ±ν production in longitudinally polarized p+p collisions at s=510 GeV using the PHENIX detector at the Relativistic Heavy Ion Collider. The cross sections are consistent with previous measurements at this collision energy, while the most forward and backward longitudinal single spin asymmetries provide new insights into the sea quark helicities in the proton. The charge of the W bosons provides a natural flavor separation of the participating partons. © 2018 authors. Published by the American Physical Society.
Cold-Nuclear-Matter Effects on Heavy-Quark Production at Forward and Backward Rapidity ind+AuCollisions atsNN=200 GeV
2014
The PHENIX experiment has measured open heavy-flavor production via semileptonic decay over the transverse momentum range 1 < p(T) < 6 GeV/c at forward and backward rapidity (1.4 < vertical bar y vertical bar < 2.0) in d + Au and p + p collisions at root s(NN) = 200 GeV. In central d + Au collisions, relative to the yield in p + p collisions scaled by the number of binary nucleon-nucleon collisions, a suppression is observed at forward rapidity (in the d-going direction) and an enhancement at backward rapidity (in the Au-going direction). Predictions using nuclear-modified-parton-distribution functions, even with additional nuclear-p(T) broadening, cannot simultaneously reproduce the data a…
Inclusive double-helicity asymmetries in neutral-pion and eta-meson production in p → + p → collisions at s =200GeV
2014
Abstract: Results are presented from data recorded in 2009 by the PHENIX experiment at the Relativistic Heavy Ion Collider for the double-longitudinal spin asymmetry, A LL , for π 0 and η production in ffiffiffi s p ¼ 200 GeV polarized p þ p collisions. Comparison of the π 0 results with different theory expectations based on fits of other published data showed a preference for small positive values of gluon polarization, Δ G , in the proton in the probed Bjorken x range. The effect of adding the new 2009 π 0 data to a recent global analysis of polarized scattering data is also shown, resulting in a best fit value Δ G ½ 0 . 05 ; 0 . 2 DSSV ¼ 0 . 06 þ 0 . 11 − 0 . 15 in the range 0 . 05 <x< …
Measurement ofΥ(1S+2S+3S)production inp+pand Au + Au collisions atsNN=200GeV
2015
Measurements of bottomonium production in heavy-ion and p + p collisions at the Relativistic Heavy Ion Collider (RHIC) are presented. The inclusive yield of the three states, (1S + 2S + 3S), was measured in the PHENIX experiment via electron-positron decay pairs at midrapidity for Au + Au and p + p collisions at root sNN = 200 GeV. The (1S + 2S + 3S) -> e(+)e(-) differential cross section at midrapidity was found to be B(ee)d sigma/dy = 108 +/- 38 (stat) +/- 15 (syst) +/- 11 (luminosity) pb in p + p collisions. The nuclear modification factor in the 30% most central Au + Au collisions indicates a suppression of the total. state yield relative to the extrapolation from p + p collision data. …