Production of forward rapidity photons in high energy heavy ion collisions

Abstract

We consider production of prompt photons in high energy gold-gold and deuterongold collisions in the forward rapidity region of RHIC (y ∼ 3.8). In this kinematics, the projectile partons typically have large x bj while the target partons are mostly at very small x bj so that the primary partonic collisions involve valence quarks from the projectile and gluons from the target. We take the target nucleus to be a Color Glass Condensate while the projectile deuteron or nucleus is treated as a dilute system of partons. We show that the photon production cross section can be written as a convolution of a quark-nucleus scattering cross section, involving a quark antiquark dipole, with the Leading Order quark-photon fragmentation function. We consider different models of the quark anti-quark dipole and show that measurement of photons in the forward rapidity region at RHIC can distinguish between different parameterizations of the dipole cross section as well as help clarify the role of parton coalescence models in hadron production at RHIC.

Testing universality of the color glass condensate descriptions

“…[32] and compare with those previously proposed to describe HERA data (for a related discussion see Ref. [36]). We observe that there are large differences in the energy and pair dipole size dependences of these models.…”

“…It was pointed out that one promising observable is the nuclear modification factor for photon production in deuteron-gold collisions at y = 3.8. In [36] it was mentioned that the KKT parameterization had not been checked against DIS data on proton targets at HERA. In this paper we perform this check.…”

Coulomb corrections to photon and dilepton production in high-energypAcollisions

“…In this and the next section we discuss photon and dilepton production in high energy pA collisions. Photon production without electromagnetic corrections was calculated in [25]. If we assume the validity of the collinear factorization on the proton side, the problem reduces to computing the photon and dilepton production in qA collisions.…”

Fresnel Zone Plate Manufacturability Analysis for Direct-Write Lithography by Simulating Focusing and Patterning Performance versus Fabrication Errors

“…Following ref. [18] we focus in the low p T region and forward rapidities, where the fragmentation contribution for photon production JHEP09(2008)019 Figure 6: Ratio between the photon and π 0 production cross sections at RHIC energies, considering two values of rapidity at RHIC (y = 2 and y = 4) and y = 6 at LHC energy. is expected to contributes significantly for the produced photons.…”