Momentum dependence of J / ψ production in proton–nucleus reactions at near-threshold beam energies

Abstract We study the inclusive J / ψ production in proton–nucleus collisions in the near-threshold energy region within the spectral function approach for incoherent primary proton–nucleon charmonium production. Our approach takes into account the effect of the nuclear J / ψ mean-field potential on these processes, as well as the elementary final state interaction (FSI) between the outgoing nucleons participating in them. We calculate the momentum dependence of the various J / ψ observables (transparency ratio, absolute and relative charmonium yields) as well as the total cross section for J / ψ production in p C, p W and p Au interactions at incident proton kinetic energies of 8, 11 and 23 GeV within the different scenarios for the J / ψ in-medium modification. We show that the transparency ratio for J / ψ mesons has an insignificant sensitivity to the J / ψ in-medium mass shift at these energies. On the other hand, our studies demonstrate that the momentum distributions (absolute and relative) for low momentum J / ψ near-threshold production in pA reactions have distinct sensitivity to the J / ψ in-medium modification. Therefore, the measurement of such observables in the CBM experiment at FAIR in the near-threshold energy domain will allow to study the modification of the charmonium properties in the nuclear medium.