Reported here are transverse single-spin asymmetries (AN) in the production of charged hadrons as a function of transverse momentum (pT) and Feynman-x (xF) in polarized p↑ + p, p↑ + Al, and p↑ + Au ...collisions at $\sqrt{^SNN}$ = 200 GeV. The measurements have been performed at forward and backward rapidity (1.4 < |η| < 2.4) over the range of 1.5 GeV /c < pT < 7.0 GeV /c and 0.04 < |xF| < 0.2. A nonzero asymmetry is observed for positively charged hadrons at forward rapidity (xF > 0) in p↑ + p collisions, whereas the p↑ + Al and p↑ + Au results show smaller asymmetries. This finding provides new opportunities to investigate the origin of transverse single-spin asymmetries and a tool to study nuclear effects in p + A collisions.
The PHENIX experiment at the Relativistic Heavy Ion Collider has measured the longitudinal double spin asymmetries, ALL, for charged pions at midrapidity (|η| < 0.35 ) in longitudinally polarized p + ...p collisions at √s = 510 GeV . These measurements are sensitive to the gluon spin contribution to the total spin of the proton in the parton momentum fraction x range between 0.04 and 0.09. One can infer the sign of the gluon polarization from the ordering of pion asymmetries with charge alone. The asymmetries are found to be consistent with global quantum-chromodynamics fits of deep-inelastic scattering and data at √s = 200 GeV , which show a nonzero positive contribution of gluon spin to the proton spin.
Presented are the first measurements of the transverse single-spin asymmetries ($A_N$) for neutral pions and eta mesons in $\textit{p}$ + Au and $\textit{p}$ + Al collisions at $\sqrt{s_{NN}}$ = 200 ...GeV in the pseudorapidity range |$\textit{η}$| < 0.35 with the PHENIX detector at the Relativistic Heavy Ion Collider. The asymmetries are consistent with zero, similar to those for midrapidity neutral pions and eta mesons produced in $\textit{p}$ + $\textit{p}$ collisions. These measurements show no evidence of additional effects that could potentially arise from the more complex partonic environment present in proton-nucleus collisions.
Polarized proton-proton collisions provide leading-order access to gluons, presenting an opportunity to constrain gluon spin-momentum correlations within transversely polarized protons and enhance ...our understanding of the three-dimensional structure of the proton. Midrapidity open-heavy-flavor production at $\sqrt{s}$ = 200 GeV is dominated by gluon-gluon fusion, providing heightened sensitivity to gluon dynamics relative to other production channels. Transverse single-spin asymmetries of positrons and electrons from heavy-flavor hadron decays are measured at midrapidity using the PHENIX detector at the Relativistic Heavy Ion Collider. These charge-separated measurements are sensitive to gluon correlators that can in principle be related to gluon orbital angular momentum via model calculations. Explicit constraints on gluon correlators are extracted for two separate models, one of which had not been constrained previously.
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 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<pT<7 GeV/c for the cross section and 1.25<pT<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. The asymmetry results are consistent with zero within uncertainties, and a model calculation based on twist-3 three-gluon correlations agrees with the data.
In 2015, the PHENIX collaboration has measured very forward (η > 6.8) single spin asymmetries of inclusive neutrons in transversely polarized proton-proton and proton-nucleus collisions at a center ...of mass energy of 200 GeV. A previous publication from this dataset concentrated on the nuclear dependence of such asymmetries. In this measurement the explicit transverse momentum dependence of inclusive neutron single spin asymmetries for proton-proton collisions is extracted using a bootstrapping unfolding technique on the transverse momenta. This explicit transverse momentum dependence will help improve the understanding of the mechanisms that create these asymmetries.
The PHENIX experiment at the Relativistic Heavy Ion Collider has measured the differential cross section, mean transverse momentum, mean transverse momentum squared of inclusive J/ψ, and cross ...section ratio of ψ(2S) to J/ψ at forward rapidity in p + p collisions at √s = 510 GeV via the dimuon decay channel. Comparison is made to inclusive J/ψ cross sections measured at √s = 200 GeV and 2.76–13 TeV. The result is also compared to leading-order nonrelativistic QCD calculations coupled to a color-glass-condensate description of the low-x gluons in the proton at low transverse momentum (pT) and to next-to-leading order nonrelativistic QCD calculations for the rest of the pTrange. These calculations overestimate the data at low pT. While consistent with the data within uncertainties above ≈ 3 GeV/c, the calculations are systematically below the data. The total cross section times the branching ratio is BR dσJ/ψpp/dy(1.2 < |y| < 2.2, 0 < pT< 10 GeV/c) = 54.3 ± 0.5 (stat) ± 5.5 (syst) nb.