Thermal radiation and inclusive production in the Kharzeev-Levin-Nardi model for ion-ion collisions

Abstract

We show that in order to obtain a successful description of the transverse momenta distribution for charged particles in ion-ion collisions, one must include a thermal emission term. The temperature of this emission T th turns out to be proportional to the saturation scale, T th = 1.8/2π Qs. The formalism for the calculation of the transverse momenta spectra in CGC/saturation approach is developed, in which two stages of the process are seen: creation of the colour glass condensate, and hadronization of the gluon jets. Our calculations are based on the observation that even for small values of pT , the main contribution in the integration over the dipole sizes stems from the kinematic region in vicinity of the saturation momentum, where theoretically, we know the scattering amplitude. Non-perturbative corrections need to be included in the model of hadronization. This model incorporates the decay of a gluon jet with effective mass m 2 eff = 2Qsµ soft where µ soft denotes the soft scale, with the fragmentation functions at all values of the transverse momenta.We use the KLN model which, provides a simple way to estimate the cross sections for the different centrality classes. Comparing the results of this paper with the transverse distribution in the protonproton scattering, we see two major differences. First, a larger contribution of the thermal radiation term is needed, in accord with higher parton densities of the produced colour glass condensate. Second, even changing the model for the hadronization, without a thermal radiation term, we fail to describe the pT spectrum. Consequently, we conjecture that the existence of the thermal radiation term is independent of the model of confinement. PACS numbers: 12.38.Cy, 12.38g,24.85.+p,25.30.Hm * We have to mention, that actually the model of hadronization with given fragmentation function describes the experimental data at large values of p T (p T ≥ 3 GeV [7] and p T ≥ 5 GeV [38]). In our model of the hadronization we assume that we can describe the data with the fragmentation function at any value of p T . We will demonstrate that such a description is possible.

High energy QCD: Multiplicity distribution and entanglement entropy

“…It has been demonstrated in Refs. [6,10,11,16] that these ideas are in qualitative and, partly, in quantitative agreement with the available experimental data.…”

“…Over the past several years, new ideas have been developed in the high energy and nuclear physics community, which suggest a robust relation between the principle features of high energy scattering and entanglement properties of the hadronic wave function [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. The main idea, which we explore in this paper, is the intimate relation between the entropy in the parton approach [18][19][20][21] and the entropy of entanglement in a proton wave function [5].…”

High energy QCD: multiplicity distribution and entanglement entropy

“…Over the past several years new ideas have been developed in the high energy and nuclear physics community, which suggest a robust relation between the principle features of high energy scattering and entanglement properties of the hadronic wave function [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. The main idea, which we explore in this paper, is the intimate relation between the entropy in the parton approach [18][19][20][21] and the entropy of entanglement in a proton wave function [5].…”

Investigating the inclusive transverse spectra in high-energy pp collisions in the context of geometric scaling framework

“…This has been investigated, for instance, in Refs. [55][56][57]. Finally, we have estimated the rapidity distribution of the produced gluons by integrating Eq.…”