Abstract
Multiple initial state parton interactions in p(d)+Au collisions are calculated in a Glauber–Eikonal formalism. The convolution of perturbative QCD parton–nucleon cross sections predicts naturally the competing pattern of low-pT suppression due geometrical shadowing, and a moderate-pT Cronin enhancement of hadron spectra. The formal equivalence to recent classical Yang–Mills calculations is demonstrated, but our approach is shown to be more general in the large x>0.01 domain because it automatically incorporates the finite kinematic constraints of both quark and gluon processes in the fragmentation regions, and accounts for the observed spectra in elementary pp→πX processes in the RHIC energy range, s∼20–200 GeV. The Glauber–Eikonal formalism can be used as a baseline to extract the magnitude of dynamical shadowing effects from the experimental data at different centralities and pseudo-rapidities.
Highlights
TinhethfreagRmHeInCtaetnioenrgryegriaonngs,e,an√dsa∼cco2u0n−ts for 200 the observed spectra in elementary pp → πX processes GeV
Interest in the Cronin effect has been revived, due to the developement of a new formulation of the physics based on the concept of gluon saturation and classical
A radical possibility was proposed in Ref. [9], that nonlinear gluon saturation may strongly suppress moderate-pT spectra at RHIC
Summary
Let’s consider a pp′ collision, where p and p′ stand for a proton (p), a deuteron (d), or a nucleon (N ). [39], we obtain a satisfactory d√escription of data for qT 5 GeV over a broad range s, but the curvature of the hadron spectrum is overpredicted in the qT = 1 − 5 GeV range As it is well known [22, 23], this can be corrected by considering an intrisic transverse momentum kT for the colliding partons [42]. By adding a small mass regulator, p0, to the exchanged transverse momentm pT Seen in this light, p0 represents the scale at which higher order parton processes enter into the game, beside the single scatterings considered in Eqs.
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