Novel mechanism of nucleon stopping in heavy ion collisions

Abstract

When a diquark does not fragment directly but breaks in such a way that only one of its quarks gets into the produced baryon, the latter is produced closer to mid rapidities. The relative size of this diquark breaking component increases quite fast with increasing energy.We show that at a given energy it also increases with the atomic mass number and with the centrality of the collision and that it allows to explain the rapidity distribution of the net baryon number (p-p) in SS central collisions. Predictions for P b-P b collisions are presented.

Production of secondaries in high-energy d+Au collisions

“…5a). A second possibility is to produce a leading meson in the first break-up of the string and a baryon in the subsequent break-up [10,25] (Fig. 5b).…”

Monte Carlo model for nuclear collisions from SPS to LHC energies

“…(see [13] for a study of evolution of particle and energy densities). Nevertheless, it is usually assumed that the enhancement of hyperons, antihyperons and φ's observed in heavy ion experiments at SPS [4,5,6,7,8] cannot be fully explained by using exclusively a mechanism which goes beyond the independent string hypothesis, as string fusion [12,16,17,18,39] or baryon junction migration [18,28,49,50,51]. In order to reproduce these experimental features rescattering of particles in the hadron gas (produced particles among themselves and with spectator nucleons) [52] has been introduced in many models.…”

“…8 [16,10] by a mechanism of color ropes which consider fusion of strings; also in the Ultra Relativistic Quantum Molecular Dynamics model [17] and in the HIJING model [18] by using an ad hoc multiplicative factor in the string tension. Also the Dual Parton Model [14], considering the possibility of creation of diquark-antidiquark pairs in the nucleon sea, together with the inclusion of diagrams which take into account baryon junction migration [49,50,51], can reproduce the experimental data (for Ω's some rescattering has still to be added). The string fusion is the main ingredient to obtain an enhancement ofΛ production and also to reproduce the Ξ data.…”

“…As discussed for strangeness enhancement, it has been pointed out that baryon junction migration [49,50,51] will enhance the stopping power due to diagrams additional to the usual ones of the Dual Parton Model. The inclusion of these diagrams also explains the SPS data.…”

Baryon Junction Stopping at the SPS and RHIC via HIJING/B

“…That mechanism has been recently included in a new version of the DPM [10]. In that model, the leading diquark is broken by a color exchange which changes its color state from a {3} to a {6}.…”