Hadrons in the nuclear medium
J/Ψ and heavy-quark production in E866/FNAL and PHENIX
P-25, MS H846, Los Alamos National Laboratory, Los Alamos NM 87545
Published online: 12 February 2004
The production of heavy quarks in nuclei is modified from that for a free nucleon by a number of nuclear effects including shadowing of the nuclear gluon distributions, energy loss of the incident gluon, and, in the case of the J/Ψ, disassociation of the pair (absorption) as it exits the nucleus. Measurements in the E866/NuSea 800 GeV fixed target experiment show a large suppression of the closed-charm yield with strong kinematical dependencies and with a slightly stronger suppression for the Ψ’ than for the J/Ψ near x F =0. On the other hand, a measurement of the D meson nuclear dependence near x F =0 shows no suppression. At RHIC the J/Ψ is thought to be a key signature for the creation of a quark-gluon plasma (QGP) in heavy-ion collisions, but the non-QGP suppression already seen in p-A collisions at lower energies shows that we must first understand these non-QGP effects on the J/Psi in order to gain a clear understanding of its production in nucleus-nucleus collisions. The most recent run at RHIC included deuteron-gold collisions and will serve as a baseline for these cold nuclear matter effects at RHIC energy. Here I report on the first results for the J/Ψ and for open-charm at PHENIX including the d-Au results. The present knowledge of gluon shadowing is very uncertain, especially in the large rapidity region of the PHENIX muon arms, and these measurements should help us determine how strong it is and perhaps even its dependence on impact parameter.
PACS: codes. – 24.85.+p - Quarks, gluons, and QCD in nuclei and nuclear processes / codes. – 25.75.-g - Relativistic heavy-ion collisions / codes. – 25.75.Dw - Particle and resonance production / codes. – 14.65.Dw - Charm quarks / codes. – 14.40.Lb - Charm mesons
© Società Italiana di Fisica, Springer-Verlag, 2004