SPS Charmonium and Bottomonium measurements

1
SPS Charm(onium) and Bottom(onium) measurements
E. Scomparin INFN Torino (Italy) Via P. Giuria 1,
I-10125 Torino (Italy)
Abstract
Heavy quark and quarkonium production are an
essential part of the heavy-ion program at SPS
energy. In particular, quarkonium production has
been studied by NA38, NA50 and, more recently, by
the NA60 experiment. The results show that in
both In-In and Pb-Pb collisions an anomalous J/?
suppression is present, i.e. suppression
mechanisms different from nuclear absorption must
be invoked to explain the observed J/? yield. The
onset of the anomalous suppression occurs at
around Npart100. From the comparison of the
centrality pattern of the J/? suppression
bewtween various systems, one can possibly single
out the physics variable, related to centrality,
that drives the J/? suppression. A first study
of open charm production, triggered by the
previous discovery (by Helios-3 and NA38/NA50)
of a dimuon excess in the intermediate mass
region (m?ltmµµltmJ/?), has been recently
performed by NA60. Preliminary results show that,
in In-In collisions, open charm production
scales, with respect to pp and pA, with the
number of nucleon-nucleon collisions. This result
implies that the intermediate mass excess is not
due to an anomalous open charm enhancement, but
rather to a prompt source. Further work, by
theory and experiment, is needed in order to
understand if thermal dimuon production can
account for the observed excess.