Event-by-event transverse momentum fluctuations in nuclear collisions at CERN SPS.

Abstract

The latest NA49 results on event-by-event transverse momentum fluctuations are presented for central Pb+Pb interactions over the whole SPS energy range (20A -158A GeV). Two different methods are applied: evaluating the Φ p T fluctuation measure and studying two-particle transverse momentum correlations. The obtained results are compared to predictions of the UrQMD model. The results on the energy dependence are compared to the NA49 data on the system size dependence. The NA61 (SHINE, NA49-future) strategy of searching of the QCD critical end-point is also discussed.

Influence of impact parameter fluctuations on transverse momentum fluctuations

“…For all five SPS energies the forward-rapidity region was selected as 1.1 < y * π < 2.6, where y * π is the particle rapidity calculated in the center-of-mass reference system (particles were not identified in this analysis and their rapidities were calculated assuming the pion mass for all particles). Within the studied rapidity range the azimuthal angle acceptance of the NA49 detector -(p T , φ) -is not uniform and it is described by the analytical curves given in [4]. Additionally, it was demonstrated [4] that at lower SPS energies, the NA49 TPC acceptance extends to the projectile spectator domain and therefore the sample of particles can be contaminated by beam particles.…”

“…Within the studied rapidity range the azimuthal angle acceptance of the NA49 detector -(p T , φ) -is not uniform and it is described by the analytical curves given in [4]. Additionally, it was demonstrated [4] that at lower SPS energies, the NA49 TPC acceptance extends to the projectile spectator domain and therefore the sample of particles can be contaminated by beam particles. For energies above 80A GeV the beam region and the region of particles -accepted by the NA49 for p T fluctuations analysisdo not overlap.…”

“…However, the preliminary NA49 results on the energy dependence of transverse momentum fluctuations over the whole SPS energy range manifests an unexpected effect: the Φ p T measure shows a different behavior for different charge selections (see [4] and Fig. 1).…”

“…The analysis presented in this article is based on preliminary NA49 results [4] and on events generated within the UrQMD approach [5,6,7].…”

Wounded-nucleon model with realistic nucleon-nucleon collision profile and observables in relativistic heavy-ion collisions

“…The statistical nature of the Glauber Monte Carlo unavoidably leads to fluctuations in the distribution of the * Maciej.Rybczynski@ujk.edu.pl † Wojciech.Broniowski@ifj.edu.pl wounded nucleons, which yield the event-by-event eccentricity fluctuations related to the fluctuations of the elliptic flow [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43], the multiplicity fluctuations as the function of the number of wounded nucleons in one of the colliding nuclei (the NA49 experiment setup [44]), and the overall size fluctuations [45], which can explain the magnitude and centrality dependence of the measured transverse-momentum fluctuations [46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61].…”