Rapidity dependence of particle densities inppandAAcollisions

Abstract

We use multiple scattering and energy conservation arguments to describe dn/dη| N A N A as a function of dn/dη| pp in the framework of string percolation. We discuss the pseudorapidity η and beam rapidity Y dependence of particle densities. We present our results for pp, Au-Au, and Pb-Pb collisions at RHIC and LHC.

Indication of change of phase in high-multiplicity proton-proton events at LHC in string percolation model

“…In this scenario of the QGP study, an unexpected feature, namely the "ridge" in the long range near side angular correlation, in distinct class of "high multiplicity" events of proton-proton collisions [10] at √ s = 7 TeV at LHC has triggered revival of an old school of thought [11][12][13][14] of the possibility of formation of a collective medium in pp collisions also. Several of subsequent theoretical and phenomenological studies [15][16][17][18][19][20][21][22][23], in different approaches, endorse the possibility, indicating the need for further investigations in understanding the high-multiplicity pp events vis-a-vis the QGP.In this article, we address the issue of collectivity in high multiplicity pp events in the framework of the String Percolation Model, that has successfully explained the collectivity and the change of phase in nucleus-nucleus collisions [24][25][26]. Also SPM describes the centre-of-mass energy dependence of mid-rapidity multiplicity [25] and the pseudorapidity distributions [26] of produced charged particles in pp collisions, for the entire range of energy, available so far.…”

“…In this article, we address the issue of collectivity in high multiplicity pp events in the framework of the String Percolation Model, that has successfully explained the collectivity and the change of phase in nucleus-nucleus collisions [24][25][26]. Also SPM describes the centre-of-mass energy dependence of mid-rapidity multiplicity [25] and the pseudorapidity distributions [26] of produced charged particles in pp collisions, for the entire range of energy, available so far.…”

“…For values of ζ t above the critical value for the 2-dimensional percolation, ζ t c (≃ 1.2 − 1.5, depending on the profile function homogeneous or Wood Saxon type), ζ t > ∼ ζ t c , one observes the formation of long strings due to fusion and stretching between the colliding nucleons. Other important quantity in SPM is the Color Suppression Factor, F(ζ t ), which is related to the particle density dN/dy and the number (N s ) of strings as:where κ is a normalization factor ∼ .63 [25] and F (ζ t ) ≡ 1−e −ζ t ζ t slows down the rate of increase in particle density with energy and with the number of strings.For pp collisions one can approximately write …”

“…Also SPM describes the centre-of-mass energy dependence of mid-rapidity multiplicity [25] and the pseudorapidity distributions [26] of produced charged particles in pp collisions, for the entire range of energy, available so far. In the SPM, the sources of multiparticle productions are the color * irais.buatista@fcfmbuap.mx strings between the colliding partons.…”

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

“…We had fixed the values of the parameters α 0.34, δ 0.84, k 1 = 1.2 to adjust the equation (7) with pp collisions data [13][14][15], with the same aim as in reference [12], and to extend the description of the pseudorapidity evolution to AA collisions [5]. As a result we have found that we are able to describe the rise with energy in AA and pp collisions with the same power-like exponent and rapidity evolution, due to the energy conservation effects which give rise to an additional energy dependence vanishing at extremely high energies.…”