Energy loss of charm quarks from J/ψ production in cold nuclear matter

Abstract

J/ψ suppression in p-A collisions is studied by considering the nuclear effects on parton distribution, energy loss of beam proton and the finial state energy loss of color octet cc̄. The leading-order computations for J/ψ production cross-section ratios RW/Be(xF) are presented and compared with the selected E866 experimental data with the cc̄ remaining colored on its entire path in the medium. It is shown that the combination of the different nuclear effects accounts quite well for the observed J/ψ suppression in the experimental data. It is found that the J/ψ) suppression on RW/Be(xF) from the initial state nuclear effects is more important than that induced by the energy loss of color octet cc̄ in the large xF region. Whether the cc̄ pair energy loss is linear or quadratic with the path length is not determined. The obtained cc̄ pair energy loss per unit path length α=2.78±0.81 GeV/fm, which indicates that the heavy quark in cold nuclear matter can lose more energy compared to the outgoing light quark.