Abstract
The charged-particle pseudorapidity density ( d N ch / d η ) for p( p ¯ )+p, p+A and A+A(B) collisions and the mean multiplicity 〈 N ch 〉 for e − +e + , e ± + p , and p( p ¯ )+p collisions are studied for a wide range of beam energies ( s ). Characteristic scaling patterns are observed for both d N ch / d η and 〈 N ch 〉 , consistent with a thermal particle production mechanism for the bulk of the soft particles created in all of these systems. The scaling patterns found also validate an essential role for quark participants in these collisions. The measured values for d N ch / d η and 〈 N ch 〉 are observed to factorize into contributions that depend on log ( s ) and the number of nucleon or quark participant pairs N pp . The quantification of these contributions gives expressions that serve to systematize d N ch / d η and 〈 N ch 〉 measurements spanning nearly 4 orders of magnitude in s and to predict their values as a function of s and N pp .
Highlights
Measurements of particle yields and kinematic distributions in electron–positron (e− +e+ ), electron–proton (e± +p), proton–proton (p(p)+p), proton–nucleus (p+A) and nucleus–nucleus (A+A(B)) collisions are essential for characterizing their global properties and to develop a good understanding of the mechanism(s) for particle production [1,2,3,4,5,6,7,8,9]
We use a large part of the available dNch /dη measurements for p+p, p+A and A+A(B) collisions, as well as the h Nch i measurements for e− +e+, e± +p, and p(p)+p collisions, to search for scaling patterns that could signal such an underlying particle production mechanism
We have performed a systematic study of the scaling properties of dNch /dη measurements for p+p, p+A and A+A(B) collisions and h Nch i measurements for e− +e+, e± +p, and p(p)+p collisions, to investigate the mechanisms for particle production in these collisions
Summary
Measurements of particle yields and kinematic distributions in electron–positron (e− +e+ ), electron–proton (e± +p), proton–proton (p(p)+p), proton–nucleus (p+A) and nucleus–nucleus (A+A(B)) collisions are essential for characterizing their global properties and to develop a good understanding of the mechanism(s) for particle production [1,2,3,4,5,6,7,8,9]. Particle production in A+A(B) collisions is frequently (but not always) described with thermodynamic and hydrodynamical models that utilize macroscopic variables such as the temperature and entropy as model ingredients This contrasts with the microscopic phenomenology (involving ladders of perturbative gluons, classical random gauge fields or strings, and parton hadronization) often used to characterize the soft collisions that account for the bulk of the particles produced in e− +e+ , e± +p, p(p)+p and p+A collisions [10,11,12,13,14]. That results from collective anisotropic flow in A+A collisions, has been observed in p+p and p+Pb collisions at the Large Hadron Collider (LHC) [15,16,17,18] and in d+Au and He+Au collisions at Relativistic Heavy Ion Collider (RHIC) [19,20] Qualitative consistency with these data has been achieved in initial attempts to describe the amplitudes of these correlations hydrodynamically [19,20,21]. We use a large part of the available dNch /dη measurements for p+p, p+A and A+A(B) collisions, as well as the h Nch i measurements for e− +e+ , e± +p, and p(p)+p collisions, to search for scaling patterns that could signal such an underlying particle production mechanism
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