Transverse energy (ET) distributions at mid-rapidity in p+p, d+Au and Au+Au collisions at √sNN=200GeV and implications for particle production models

Abstract

Measurements of the mid-rapidity transverse energy distribution dET/dη are presented for p+p, d+Au, and Au+Au collisions at √sNN=62.4-200GeV. The ET distributions are compared with the number of participants, Npart, the number of constituent-quark participants, Nqp, and the number of color-strings (Additive Quark Model - AQM) calculated from a Glauber model. For Au+Au, 〈dET/dη〉/(0.5Npart) increases with Npart, while 〈dET/dη〉/Nqp is approximately constant vs. centrality for √sNN≥62.4GeV. This indicates that the two component ansatz, dETAA/dη=(dETpp/dη)[(1-x)Npart/2+xNcoll], which has been used to represent ET distributions, is simply a proxy for Nqp, and that the Ncoll term does not represent a hard-scattering component in ET distributions. The dET/dη distributions of d+Au, and Au+Au are calculated from the measured p+p ET distribution using two models (AQM and Nqp) that both reproduce the Au+Au data. For the asymmetric d+Au system, the Nqp model reproduces the data while the AQM does not.