The PHENIX experiment at the Relativistic Heavy Ion Collider has measured the differential cross section of φ(1020)-meson production at forward rapidity in p+p collisions at s=510 GeV via the dimuon ...decay channel. The partial cross section in the rapidity and pT ranges 1.2
Asymmetric nuclear collisions of p+Al, p+Au, d+Au, and He3+Au at sNN=200 GeV provide an excellent laboratory for understanding particle production, as well as exploring interactions among these ...particles after their initial creation in the collision. We present measurements of charged hadron production dNch/dη in all such collision systems over a broad pseudorapidity range and as a function of collision multiplicity. A simple wounded quark model is remarkably successful at describing the full data set. We also measure the elliptic flow v2 over a similarly broad pseudorapidity range. These measurements provide key constraints on models of particle emission and their translation into flow.
We report the transverse single-spin asymmetries of J/ψ production at forward and backward rapidity, 1.2 < | y | < 2.2 , as a function of J/ψ transverse momentum (pT) and Feynman- x (xF). The data ...analyzed were recorded by the PHENIX experiment at the Relativistic Heavy Ion Collider in 2015 from p+p, p+Al, and p+Au collisions with transversely polarized proton beams at $\sqrt{s}$$_ {NN}$ = 200 GeV . At this collision energy, single-spin asymmetries for heavy-flavor particle production of p + p collisions provide access to the spin-dependent gluon distribution and higher-twist correlation functions inside the nucleon, such as the gluon Qiu-Sterman and trigluon correlation functions. Proton + nucleus collisions offer an excellent opportunity to study nuclear effects on the correlation functions. The data indicate a positive asymmetry at the two-standard-deviation level in the p+p data for 2 GeV / c < pT < 10 GeV / c at backward rapidity and negative asymmetries at the two-standard-deviation level in the p + Au data for pT < 2 GeV/c at both forward and backward rapidity, while in p + Al collisions the asymmetries are consistent with zero within the range of experimental uncertainties.
Here, we present measurements of the transverse-momentum dependence of elliptic flow v2 for identified pions and (anti)protons at midrapidity (|η| < 0.35), in 0%–5% central p+Au and 3He+Au collisions ...at √sNN = 200 GeV. When taken together with previously published measurements in d + Au collisions at √sNN = 200 GeV, the results cover a broad range of small-collision-system multiplicities and intrinsic initial geometries. We observe a clear mass-dependent splitting of v2(pT) in d + Au and 3He + Au collisions, just as in large nucleus-nucleus (A + A) collisions, and a smaller splitting in p + Au collisions. Both hydrodynamic and transport model calculations successfully describe the data at low pT (< 1.5GeV/c), but fail to describe various features at higher pT. In all systems, the v2 values follow an approximate quark-number scaling as a function of the hadron transverse kinetic energy per constituent quark (KET/nq), which was also seen previously in A + A collisions.
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