Abstract
Abstract The effects of parton energy loss in cold nuclear matter on heavy-quarkonium suppression in p-A collisions are studied. It is shown from first principles that at large quarkonium energy E and small production angle in the nucleus rest frame, the medium-induced energy loss scales as E. Using this result, a phenomenological model depending on a single free parameter is able to reproduce J/ψ and Υ suppression data in a broad x F -range and at various center-of-mass energies. These results strongly support energy loss as the dominant effect in heavy-quarkonium suppression in p-A collisions. Predictions for J/ψ and Υ suppression in p-Pb collisions at the LHC are made. It is argued that parton energy loss scaling as E should generally apply to hadron production in p-A collisions, such as light hadron or open charm production.
Highlights
Parton through the hot medium and qhot the rate per unit length of transverse momentum broadening in the medium
New scaling properties have been identified for the induced gluon radiation spectrum dI/dω, and associated energy loss ∆E, of hard processes where a color charge undergoes small angle scattering through a static medium [15]
We stressed that the effect of saturation alone fails in describing J/ψ nuclear suppression at different collision energies
Summary
We will show that the available large-xF quarkonium suppression data in p–A collisions can be explained by parton energy loss in cold matter. In the present study we will assume for simplicity that the octet QQpair arises dominantly from the splitting of an incoming gluon This should be a valid assumption for all p–A data considered in this paper, except at very large values of xF (xF ∼> 0.8), where quark-induced processes come into play. To make the physics under consideration clear, let us mention that the spectrum (1.2) is not expected in quarkonium (real or virtual) photoproduction, nor in inclusive deep inelastic scattering (DIS) off nuclei, where the incoming energetic particle participating to the hard subprocess is colorless (see figure 1c for the DIS case).5 In those cases radiation with tf ≫ thard can only arise from final state radiation.
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