Abstract

We present the first study of the energy dependence of pt angular correlations inferred from event-wisemean transversemomentum p(t)> fluctuations in heavy ion collisions. We compare our large-acceptance measurements at CM energies root s(NN) = 19.6, 62.4, 130 and 200 GeV to SPS measurements at 12.3 and 17.3 GeV. p(t) angular correlation structure suggests that the principal source of pt correlations and fluctuations is minijets (minimum-bias parton fragments). We observe a dramatic increase in correlations and fluctuations from SPS to RHIC energies, increasing linearly with 1n root s(NN) from the onset of observable jet-related p(t)> fluctuations near 10 GeV.