Di-photon correlations in p+A collisions at the LHC

We study the long-range in rapidity near-side and away-side azimuthal collimation, the so-called “ridge” structure for di-photon correlations in high-energy proton-nucleus (p+A) collisions. We show that based on the initial-state Color-Glass-Condensate at leading-log approximation, the ridge-like structure for di-photon correlations disappears at the LHC energies. Nevertheless, the near-side and away-side correlations coming from the remanent of double and single fragmentation contributions respectively, survive upto Δη≈1÷3 in rapidity interval between two produced photons at RHIC and the LHC. Therefore, an experimental observation of ridge-like structure in di-photon correlations at the LHC similar to the one observed in di-hadron correlations in p+p(A) collisions, may suggest that final-state effects play important role in the formation of the ridge.