Abstract:
The centrality dependence of the antiproton
per participant
ratio is studied in Pb(160 AGeV)+Pb
reactions. Antiproton
production in collisions of heavy nuclei at
the CERN/SPS
seems considerably enhanced as compared to
conventional
hadronic physics, given by the antiproton
production rates
in $pp$ and antiproton annihilation in
$\bar{p}p$ reactions.
This enhancement is consistent with the
observation of
strong in-medium effects in other hadronic
observables and
may be an indication of partial restoration
of chiral symmetry.