Measurement of the mid-rapidity transverse energy distribution from $\sqrt{s_{_{NN}}}=130$ GeV Au+Au collisions at RHIC

The first measurement of energy produced transverse to the beam direction at RHIC is presented. The mid-rapidity transverse energy density per participating nucleon rises steadily with the number of participants, closely paralleling the rise in charged-particle density, such that E_T / N_ch remains relatively constant as a function of centrality. The energy density calculated via Bjorken's prescription for the 2% most central Au+Au collisions at sqrt(s_NN)=130 GeV is at least epsilon_Bj = 5.0 GeV/fm^3 which is a factor of 1.7 larger than found at sqrt(s_NN)=17.2 GeV (Pb+Pb at CERN).