J/ψ production in sNN=200GeV Cu+Cu collisions

Abstract

Yields for J=c production in Cu þ Cu collisions at ffiffiffiffiffiffiffiffi sNN p ¼ 200 GeV have been measured over the rapidity range jyj < 2:2 and compared with results in p þ p and Au þ Au collisions at the same energy. The Cu þ Cu data offer greatly improved precision over existing Au þ Au data for J=c production in collisions with small to intermediate numbers of participants, in the range where the quark-gluon plasma transition threshold is predicted to lie. Cold nuclear matter estimates based on ad hoc fits to d þ Au data describe the Cu þ Cu data up to Npart 50, corresponding to a Bjorken energy density of at least 1:5 GeV=fm3.