Charmonium suppression in p A collisions

The new high precision data on charmonium production in proton-nucleus collisions by the E866/NuSea Collaboration at Fermilab allow us---together with older data at lower energies---to fix a unique set of parameters for the standard production and absorption scenario of charmonium in a proton-nucleus reaction. In this scenario the $c\overline{c}$ pair is formed in an octet state, emits a gluon, and continues its radial expansion in a singlet state until it has reached the charmonium radius. In all three phases it can interact with the nuclear environment. We find that the lifetime of the octet state is much shorter than acceptable on physical grounds. This challenges the physical reality of the first phase in the standard scenario.