Constituent quarks and systematic errors in mid-rapidity charged multiplicity dNch/dη distributions

Abstract

Centrality definition in A+A collisions at colliders such as RHIC and LHC suffers from a correlated systematic uncertainty caused by the efficiency of detecting a p+p collision (50 ± 5% for PHENIX at RHIC). In A+A collisions where centrality is measured by the number of nucleon collisions, N coll , or the number of nucleon participants, N part , or the number of constituent quark participants, N qp , the error in the efficiency of the primary interaction trigger (Beam-Beam Counters) for a p+p collision leads to a correlated systematic uncertainty in N part , N coll or N qp which reduces binomially as the A+A collisions become more central. If this is not correctly accounted for in projections of A+A to p+p collisions, then mistaken conclusions can result. A recent example is presented in whether the mid-rapidity charged multiplicity per constituent quark participant (dN ch /dη)/N qp in Au+Au at RHIC was the same as the value in p+p collisions.

Forward-backward multiplicity fluctuations in ultrarelativistic nuclear collisions with wounded quarks and fluctuating strings

“…where N ch is the number of charged hadrons in a midrapidity bin, and N i are the average numbers of wounded quarks in nucleus i in a considered centrality class. The proportionality constant k should not depend on centrality or the mass numbers of the nuclei (i.e., on the overall number of participants), and indeed this requirement is satisfied to expected accuracy [22,28]. Of course, k increases with the collision energy.…”

“…The idea (see [2] for a discussion of the foundations), adopts the Glauber model [3] in its variant suitable for inelastic collisions [4]. Whereas the wounded nucleon scaling [5], when applied to the highest BNL Relativistic Heavy-Ion Collider (RHIC) or the CERN Large Hadron Collider (LHC) energies, requires a sizable admixture of binary collisions [6,7], the scaling based on wounded quarks [8][9][10][11] works remarkably well [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. Another successful approach [29,30] amends the wounded nucleons with a meson-cloud component.…”

Studies and Simulations of PbPb Collisions at sNN=2.76 TeV with the Glauber Monte Carlo Model

“…For each shell, we take its outer radius, and put that value into equation 1 to approximate the nucleon density of each shell. The nuclear charge density is parameterized by a Fermi distribution [10] with three parameters, nucleon radius R being 6.62 fm, skin depth a being 0.546 fm, and deviation from a spherical shape, w being 0 for lead: [3]…”

Longitudinal correlations from fluctuating strings in Pb-Pb, p -Pb, and p−p collisions

“…We use the fact that the multiplicity of the produced hadrons is successfully described within the wounded picture [12], which is an adoption of the Glauber theory [13] to inelastic collisions [14]. Moreover, the wounded quark scaling [15][16][17][18] has been shown to work surprisingly well [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] at both RHIC and the LHC collision energies. Extensions to more partons per nucleon than just three quarks have also been considered, with the conclusion that the increase in energy yields more wounded partons [29].…”