Pseudorapidity Dependence of Particle Production and Elliptic Flow in Asymmetric Nuclear Collisions of p+Al , p+Au , d

Abstract

1 nuclear collisions of p+Al, p+Au, d+Au, and 3 He+Au at √ s N N = 200 GeV 2 121 4Asymmetric nuclear collisions with a light projectile nucleus striking a heavier target nucleus have proven to be an 123 excellent testing ground for particle production models and the longitudinal dynamics following the initial collision -124 for an early review see Ref. [1]. Many calculations have successfully described the longitudinal (or rapidity) distribution 125 of produced particles in proton-nucleus (p+A) collisions via the fragmentation of color strings and with counting rules 126 based on the number of "wounded" or struck nucleons or quarks in the projectile and target. Recently, a proposal 127 for testing the wounded-quark model [2] was put forth that specifically called for the measurement of dN ch /dη over a 128 broad range of pseudorapidity in p+Au, d+Au, and 3 He+Au collisions [3]. Fully three-dimensional hydrodynamical 129 models also require input on the longitudinal distribution of initial deposited energy and gradients thereof [4]. Once 130 the initial partons or fluid elements are populated, the models evolve the system dynamically. Measurements of elliptic 131 flow as a function of pseudorapidity provide constraints on the longitudinal dynamics of the evolution. 132As the incoming hadrons or nuclei break up, the rapidity distribution of liberated partons may be determined by 133 the longitudinal parton distribution functions [5, 6] or via a universal color field breakup for each struck nucleon 134 or quark [7]. For that reason, calculations based on Monte Carlo Glauber models have been developed to calculate 135 the number of struck nucleons and struck quarks (see for example Refs. [8-10]). The PHOBOS collaboration has 136 previously published charged hadron dN ch /dη measurements over |η| < 5.4 in d+Au collisions at √ s N N = 200 GeV [11]. 137 PHENIX has also published dN ch /dη measurements in high-multiplicity d+Au collisions at √ s N N = 200, 62, 39, and 138 19.6 GeV [12]. The wounded-quark model has been constrained by the d+Au data and found to be in reasonable 139 agreement with the centrality dependence, while the wounded-nucleon model cannot describe the data [3]. A crucial 140 test of the wounded-quark model is to see if it is universal across different colliding systems. Additional measurements 141 in light and heavy systems at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC) can 142 also be tested in this context-see for example different geometry tests in Refs. [13-15]. 143 157 section of 2.30, 2.26, 1.76, 0.54 barns for 3 He+Au, d+Au, p+Au, and p+Al respectively. The dN ch /dη analysis has 158 negligible statistical uncertainties and thus a subset of runs with the most stable detector configuration are utilized 159and the run-to-run variation is used in the determination of systematic uncertainties. For the elliptic flow v 2 analysis 160 in high-multiplicity events, also referred to as central events, an additional trigger was used that required the number 161 of fi...

Creation of quark–gluon plasma droplets with three distinct geometries

“…Shown in Fig. 4 are the previously published d+ Au (20-40%) and p+ Au (0-5%) v 2 where the measured mean charged particle multiplicities (dN ch /dη) match 38 . The results do not support the MSTV prediction of an identical v 2 for these two systems at the same multiplicity, while the differences in v 2 between the systems follow the expectations from hydrodynamic calculations matched to the same dN ch /dη.…”

“…Any methods, additional references, Nature Research reporting summaries, source data, statements of data availability and associated accession codes are available at https://doi.org/10.1038/ s41567-018-0360-0. 38 . Blue and red curves correspond to SONIC predictions for d+ Au and p+ Au, respectively.…”

Exploring new small system geometries in heavy ion collisions

“…For small system collisions at √ s N N = 200 GeV at RHIC, a nucleon-nucleon inelastic cross section of 42 mb is employed, and the scale factor is determined so as to match the measured dN ch /dη at midrapidity in 3 He+Au collisions measured by the PHENIX experiment [35]. The identical parameter set, including this scale factor, is utilized for all the RHIC collision system predictions.…”

PHENIX results on system size dependence of J/$\psi$ nuclear modification in $p, d,$ $^3$He+A collisions at $\sqrt{s_{\rm NN}}$=200 GeV

“…2), we see a suppression at low p T that disappears with increasing p T . It is interesting to note that the modification is the same (within uncertainties) for both systems, despite the factor of ∼2 difference in the number of produced charged particles dN ch /dη between these system [12]. This may suggest that, over this range of dN ch /dη, late stage breakup of J/ψ is not sensitive to the co-moving particle density within these uncertainties.…”

“…This allows us to experimentally vary the initial state effects that charm quarks may be subject to. By changing the projectile between p, d, and 3 He, we can experimentally vary the number of produced particles that co-move with the charmonium state outside the nucleus [12], which may affect the level of breakup that occurs in the late stages of the collision.…”