Rapidity dependence of particle densities in pp and AA collisions in the string percolation approach

Abstract

Abstract. We use multiple scattering and energy conservation arguments to describe dn/dn N A N A as a function of dn/dn pp in the framework of string percolation.As nuclei are made up of nucleons it is natural to look at nucleus-nucleus (A-A) collisions as resulting from the superposition of nucleon-nucleon (p-p) collisions, in the spirit of Glauber model approach. In the single scattering limit the average number of participating nucleons per nucleus, N A behave incoherently and the multiplicity at low energy corresponds to the wounded nucleon modelThe equation (1) does not agree in general with data. At higher energies one has to take into account multiple scattering to obtain dn dywhere N 1+α(s)A is the estimated total number of nucleon-nucleon collisions and single scattering was subtracted [4]. It can be noticed that the energy momentum conservation constrains the combinatorial factors of the Glauber calculus at low energy. We address the problem of the energy momentum of the N A valence strings shared by N 4/3 A mostly sea strings, by reducing the effective number of sea strings rather than reducing the sea plateau. We write [4][5]we are back to the wounded nucleon model, and for √ s >> √ s 0 , α( √ s) → 1 3 , we have fully developed Glauber calculus. Here as in [2] [3] our framework is the Dual Parton Model with parton saturation, and we work with Schwinger strings, with fusion and percolation [6]. In this framework the interactions in N A N A collisions occur with the formation of longitudinal color strings in rapidity, stretched between the partons of the projectile and the target. In the impact parameter plane due to the confinement, the color of strings is confined to small area in transverse space S 1 = πr 2 0 with r 0 ∼ .2 − .3 fm, these strings decay into new ones by qq −qq pair production and subsequently hadronize to produce the observed hadrons. a

De-confinement and clustering of color sources in nuclear collisions

“…In percolation the multiplicity per participant is almost independent of N A as well and the only additional dependence arises from the factor (1 − exp(−ξ)) 1/2 which grows weakly with N A above the percolation threshold. Concerning the energy dependence, Q 2 s behaves like s λ , so Figure 13: Comparison of results from the evolution of dn ch /dη with dependence on pseudorapidity for pp collisions at different energies (lines) [119].…”

“…12 The evolution outside the central rapidity region has been studied extensively extending to all rapidities Eq. ( 96) [116,117,118,119]: where J is the Jacobean…”

“…Equations ( 118) and (119) give the distributions for any projectile, target, energy and degree of centrality and are universal functions which depend only on two parameters < p 2 t > 1 and < n > 1 the transverse momentum and multiplicity of particles produced by one string. In the case of identified secondary particles the corresponding quantities for each identified particle, < p 2 t > 1i and < n > 1i should be used.…”

String percolation in AA and p+p collisions

“…The evolution outside the central rapidity region has been studied extensively extending Eq. ( 43) to all rapidities [90,91,92,93,94,95]. The limiting fragmentation property is not satisfied exactly.…”

On Current Conversion between Particle Rapidity and Pseudorapidity Distributions in High Energy Collisions

“…High energy collisions are an important research field in particle and nuclear physics. In the collisions, a lot of particles are produced, and the rapidity and/or pseudorapidity distributions can be obtained and studied [1][2][3]. Usually, one needs to do a conversion between the rapidity and pseudorapidity distributions in the case of only one of the two distributions being obtained.…”