Measurement of beam energy dependent nuclear modification factors at STAR

TL;DR

This paper measures nuclear modification factors at various energies in heavy-ion collisions to understand medium effects like quark-gluon plasma formation and the Cronin Effect, comparing results with theoretical models.

Contribution

It provides new measurements of R_{CP} for charged hadrons and identified particles across a range of energies, and discusses methods to disentangle different nuclear effects.

Findings

Observation of high transverse momentum particle yield enhancement in d+Au collisions.

Charged-hadron R_{CP} measured at multiple energies from 7.7 to 62.4 GeV.

Comparison with HIJING suggests potential methods to separate different nuclear modifications.

Abstract

The nuclear modification factors R_{AA} and R_{CP} have been used to measure medium-induced suppression in heavy-ion collisions at sqrt{s_{NN}} = 200GeV which was among the earliest evidence for the existence of a strongly interacting medium called a quark-gluon plasma (QGP). Nuclear modification factors for asymmetric collisions (R_{dA}) have measured the Cronin Effect, an enhancement of high transverse momentum particle yields in deuteron-gold collisions relative to proton-proton collisions. A similar enhancement is observed in data presented in these proceedings and competes with the quenching caused by partonic energy loss in the QGP. In these proceedings we will present charged-hadron R_{CP} at mid-rapidity for sqrt{s_{NN}} = 7.7 - 62.4GeV as well as identified pi^{+}, K^{+}, and proton R_{CP}. Comparisons to HIJING motivate possible methods for disentangling competing modifications to nuclear transverse momentum spectra.