Prompt photonjet angular correlations at central rapidities in p +A collisions
Abstract
Photonjet azimuthal correlations in protonnucleus collisions are a promising tool for gaining information on the gluon distribution of the nucleus in the regime of nonlinear color fields. We compute such correlations from the process g →q q ¯ γ in the rapidity regime where both the projectile and target lightcone momentum fractions are small. By integrating over the phase space of the quark which emits the photon, subject to the restriction that the photon picks up most of the transverse momentum (to pass an isolation cut), we effectively obtain a g +A →q γ process. For nearly backtoback photonjet configurations we find that it dominates over the leadingorder process q +A →q γ by two less powers of Q_{⊥}/Q_{S}, where Q_{⊥} and Q_{S} denote the net photonjet pair momentum and the saturation scale of the nucleus, respectively. We determine the transversemomentumdependent gluon distributions involved in g +A →q γ and the scale where they are evaluated. Finally, we provide analytic expressions for ⟨cos n ϕ ⟩ moments, where ϕ is the angle between Q_{⊥} and the average photonjet transverse momentum P_{∼ ⊥} , and first qualitative estimates of their transverse momentum dependence.
 Publication:

Physical Review D
 Pub Date:
 January 2018
 DOI:
 10.1103/PhysRevD.97.014012
 arXiv:
 arXiv:1710.01991
 Bibcode:
 2018PhRvD..97a4012B
 Keywords:

 High Energy Physics  Phenomenology
 EPrint:
 v3: more elaborated discussions on photon isolation cut, a few new references, results unchanged, accepted for publication in PRD