Event-wise pt fluctuations in Au-Au collisions at sNN=130 GeV

Abstract

We present the first large-acceptance measurement of event-wise mean transverse momentum ?pt? fluctuations for Au-Au collisions at nucleon-nucleon center-of-momentum collision energy sNN = 130 GeV. The observed nonstatistical ?pt?fluctuations substantially exceed in magnitude fluctuations expected from the finite number of particles produced in a typical collision. The r.m.s. fractional width excess of the event-wise ?pt?distribution is 13.7±0.1(stat) ±1.3(syst)% relative to a statistical reference, for the 15% most-central collisions and for charged hadrons within pseudorapidity range |η|<1,2π azimuth, and 0.15≤pt≤2 GeV/c. The width excess varies smoothly but nonmonotonically with collision centrality and does not display rapid changes with centrality which might indicate the presence of critical fluctuations. The reported ?pt? fluctuation excess is qualitatively larger than those observed at lower energies and differs markedly from theoretical expectations. Contributions to ?pt? fluctuations from semihard parton scattering in the initial state and dissipation in the bulk colored medium are discussed. © 2005 The American Physical Society.