Authors
Abdallah, M. S. ; Aboona, B. E. ; Adam, J. ; Adamczyk, L.; Adams, J. R. ; Adkins, J.; Agakishiev, G.; Aggarwal, I.; Aggarwal, M.; Ahammed, Z.; Spinka, H. M.; Underwood, D.G.; Zurek, M.
Abstract
We report cumulants of the proton multiplicity distribution from dedicated fixed-target Au+Aucollisions at sNN = 3.0 GeV, measured by the STAR experiment in the kinematic acceptance ofrapidity (y) and transverse momentum (pT) within 0.5 < y < 0 and 0.4 < pT < 2.0 GeV/c. Inthe most central 05% collisions, a proton cumulant ratio is measured to be C4/C2 = 0.85 0.09 (stat.)0.82 (syst.), which is 2 below the Poisson baseline with respect to both the statisticaland systematic uncertainties. The hadronic transport UrQMD model reproduces our C4/C2 in themeasured acceptance. Compared to higher energy results and the transport model calculations,the suppression in C4/C2 is consistent with fluctuations driven by baryon number conservation andindicates an energy regime dominated by hadronic interactions. These data imply that the QCDcritical region, if created in heavy-ion collisions, could only exist at energies higher than 3 GeV.