Charged-particle multiplicity and pseudorapidity distributions measured with the PHOBOS detector inAu+Au,Cu+Cu,

Abstract

Pseudorapidity distributions of charged particles emitted in Au + Au, Cu + Cu, d + Au, and p + p collisions over a wide energy range have been measured using the PHOBOS detector at RHIC. The centrality dependence of both the charged particle distributions and the multiplicity at midrapidity were measured. Pseudorapidity distributions of charged particles emitted with |η| < 5.4, which account for between 95% and 99% of the total charged-particle emission associated with collision participants, are presented for different collision centralities. Both the midrapidity density, dN ch /dη, and the total charged-particle multiplicity, N ch , are found to factorize into a product of independent functions of collision energy, √ s N N , and centrality given in terms of the number of nucleons participating in the collision, Npart. The total charged particle multiplicity, observed in these experiments and those at lower energies, assumes a linear dependence of (ln s N N ) 2 over the full range of collision energy of √ s N N =2.7-200 GeV.

Transverse energy production and charged-particle multiplicity at midrapidity in various systems fromsNN=7.7to 200 GeV

“…Measurements of dN ch /dη in systems lighter than Au have been published by PHOBOS for 200 GeV and 62.4 GeV Cu+Cu collisions [17], showing that the Cu+Cu dN ch /dη distribution as a function of N part exhibits similar features when compared to Au+Au collisions. Here, those measurements are extended to include measurements of dE T /dη and the addition of measurements from the asymmetric Cu+Au system at √ s N N = 200 GeV.…”

“…For (dE T /dη)/(0.5N part ), data are shown from FOPI 0-1% centrality Au+Au collisions [27], E802 0%-5% centrality Au+Au collisions [28], NA49 0-7% centrality Pb+Pb collisions [29,30], STAR 0%-5% centrality Au+Au collisions [18], and CMS 0%-5% centrality Pb+Pb collisions [30]. For (dN ch /dη)/(0.5N part ), data are shown from FOPI [27], E802 [28,31,32], NA49 [29], STAR [18,33], PHO-BOS 0-3% centrality Au+Au collisions [17], ALICE 0%-5% centrality Pb+Pb collisions [34], and ATLAS [35] Pb+Pb collisions interpolated to 0%-5% centrality. The data are plotted on a log-log scale to illustrate the power law behavior of both (dE T /dη)/(0.5N part ) and (dN ch /dη)/(0.5N part ) as a function of log( ply as E T /N ch , is a variable that is related to the average transverse mass of the produced particles [3].…”

Measurement of the relative yields of ψ(2S) to ψ(1S) mesons produced at forward and backward rapidity in Adare1, Aidala2, Ajitanand3 et al. 2017Phys. Rev. CSelf Cite

“…The mechanism for this preferential suppression of the ψ(2S) relative to the ψ(1S) is expected to occur after the ψ(1S) formation time. A significant difference in the late stages of the collision between this region and forward rapidity is the presence of a larger number of comoving hadrons (see [46] for measurements of the charged particle rapidity distributions in d+Au, a similar collision system). Once the cc pair exits the nucleus, it may be subject to interactions with these particles that can lead to breakup of the charmonium state, which are expected to be more pronounced on the less tightly bound ψ(2S).…”

Dependence on pseudorapidity and on centrality of charged hadron production in PbPb collisions at $ \sqrt {{{s_{\text{NN}}}}} = 2.76 $ TeV

“…The PHENIX and PHOBOS points are taken from refs. [21] and [33], their error bars representing both the statistical and systematic uncertainties. Systematic uncertainties of the measurements from this analysis are shown as an error band, while the statistical uncertainties are negligible.…”