High Transverse Momentum Hadron Spectra at sqrt{s_{NN}}=17.3 GeV, in Pb+Pb and p+p Collisions

TL;DR

This study measures high transverse momentum hadron spectra in Pb+Pb and p+p collisions at 17.3 GeV, revealing the dominance of the Cronin effect and comparing nuclear modification factors to higher energy RHIC results.

Contribution

First measurement of high pT hadron spectra at SPS energies, analyzing nuclear modification factors and comparing them to RHIC results to understand energy dependence.

Findings

R_{AA} increases rapidly with pT, indicating Cronin effect dominance.

R_{CP} saturates below unity, showing suppression similar to RHIC at lower pT.

Suppression at high pT is less pronounced than at RHIC energies.

Abstract

Transverse momentum spectra up to 4.5 GeV/c around midrapidity of pi^{+/-}, p, pbar, K^{+/-} in Pb+Pb reactions were measured at sqrt{s_{NN}}=17.3 GeV by the CERN-NA49 experiment. The nuclear modification factors R_{AA} for pi^{+/-} and R_{CP} for pi^{+/-},p,pbar,K^{+/-} were extracted and are compared to RHIC results at sqrt{s_{NN}}=200 GeV. The modification factor R_{AA} shows a rapid increase with transverse momentum in the covered region. This indicates that the Cronin effect is the dominating effect in our energy range. The modification factor R_{CP}, in which the contribution of the Cronin effect is reduced, shows a saturation well below unity in the pi^{+/-} channel. The extracted R_{CP} values follow the 200 GeV RHIC results closely in the available transverse momentum range, except for pi^{+/-} above 2.5 GeV/c transverse momentum. There the measured suppression is smaller than that observed at RHIC.