Geometrical Scaling of Direct Photons in Relativistic Heavy Ion and d+Au Collisions

Abstract

In this paper, we show that multiplicity spectra of direct photons in A+A and d+Au collisions at different centrality classes and different energies exhibit geometrical scaling, {\em i.e.}, they depend on a specific combination of number of participants $N_{\mathrm{part}}$, collisions energy $W$, and transverse momentum $p_T$ -- called saturation scale -- rather than on all these three variables separately. In particular, the dependence on the geometry of collisions encoded in the dependence on $N_{\mathrm{part}}$ is in agreement with the expectations based on the Color Glass Condensate theory.

9 pages, 6 figures

References in corpus (5)

• Multi-messenger heavy-ion collision physics
• Saturation and Scaling of Multiplicity, Mean p_T and p_T Distributions from 200 GeV < sqrt{s} < 7 TeV - Addendum
• Benchmarking a Non-Equilibrium Approach to Photon Emission in Relativistic Heavy-Ion Collisions
• A Phenomenological Model of the Glasma and Photon Production
• Geometrical scaling of prompt photons in heavy ion collisions