Cronin effect in the Drell-Yan reaction

Abstract

We explore the mechanism of transverse momentum broadening of fast quarks propagating in nuclei, using Drell-Yan (DY) transverse momentum distributions measured in the experiment E866 at FermiLab with beams of 800 GeV protons. Our theoretical analysis is based on the color dipole approach in the target rest frame, which has provided a successful phenomenological description of a variety of hadronic reactions. The present application is relevant to the regime of short coherence length (SCL), where the spatial extent of the fluctuations of the projectile responsible for the Drell-Yan reaction is short compared to the internucleon spacing. In this limit, momentum broadening comes from initial state interactions and is described as color filtering, i.e. absorption of large-size dipoles leading to diminished transverse separation and hence enhanced transverse momentum. The predictions we present are in good agreement with the E866 data. The interactions leading to the acquisition of transverse momentum arise from the color-dipole cross section determined previously from deep-inelastic scattering on proton targets. Aside from the determination of the color-dipole cross section, no other phenomenological input is needed to explain the experimental results. The mean-square momentum broadening of dileptons determined in a recent separate analysis of the data is likewise well described by our theory. These results confirm that the origin of momentum broadening in DY is the color dipole cross section mediating soft initial state interactions between the parton of the projectile that initiates the reaction and the nucleons of the nucleus, as provided by the color dipole description. Predictions for broadening observables at RHIC are presented.

LATEX, 30 pages, 12 figures; figures updated and discussion added in Sect. 2

References in corpus (7)

• Breakdown of QCD factorization at large Feynman x
• Initial State Parton Broadening and Energy Loss Probed in d+Au at RHIC
• Dilepton low $p_T$ suppression as an evidence of the Color Glass Condensate
• Nuclear Broadening of Transverse Momentum in Drell-Yan Reactions
• Investigating the Drell-Yan transverse momentum distribution in the color dipole approach
• Relating different approaches to nuclear broadening
• Using dileptons to probe the Color Glass Condensate

Cited by in corpus (8)

• Measuring the saturation scale in nuclei
• Drell-Yan phenomenology in the color dipole picture revisited
• Isolated photon production and pion-photon correlations in high-energy $pp$ and $pA$ collisions
• Nuclear effects in Drell-Yan pair production in high-energy $pA$ collisions
• Evaluating Results from the Relativistic Heavy Ion Collider with Perturbative QCD and Hydrodynamics
• Drell-Yan process in $pA$ collisions: the exact treatment of coherence effects
• Nuclear suppression of dileptons at forward rapidities
• Nuclear Suppression of Dileptons at Large xF