Coherent QCD multiple scattering in proton-nucleus collisions

Abstract

We argue that high energy proton-nucleus (p+A) collisions provide an excellent laboratory for studying nuclear size enhanced parton multiple scattering where power corrections to the leading twist perturbative QCD factorization approach can be systematically computed. We identify and resum these corrections and calculate the centrality and rapidity dependent nuclear suppression of single and double inclusive hadron production at moderate transverse momenta. We demonstrate that both spectra and dihadron correlations in p+A reactions are sensitive measures of such dynamical nuclear attenuation effects

Figures (3)

• Figure 1: Coherent multiple scattering of the struck parton in deeply inelastic scattering (a) and in proton-nucleus collisions (b). A set of resummed two gluon exchange diagrams (c) in p+A reactions.
• Figure 2: Top: suppression of the single and double inclusive hadron production rates in d+Au reactions versus $p_T$ for rapidities $y_1 = 0,1,2,3$ and $4$. $\xi^2 = 0.12$ GeV$^2$. Data on forward rapidity $h^-$ attenuation is from BRAHMS Arsene:2004ux. Bottom: impact parameter dependence of the calculated nuclear modification for central $b=3$ fm, minimum bias $b_{\rm min.bias}=5.6$ fm and peripheral $b=6.9$ fm collisions. The trigger hadron $p_{T1}=1.5$ GeV, $y_1 = 3$ and the associated hadron $y_2=0$.
• Figure 3: Left: centrality dependence of $C_2(\Delta \varphi)$ at moderate $p_{T_1}=4$ GeV, $p_{T_2}=2$ GeV and rapidities $y_1=0,2$ and $y_2=0$. Central d+Au and p+p data from STAR Adams:2003im. Right: $C_2({\Delta \varphi})$ at small transverse momenta $p_{T_1}=1.5$ GeV, $p_{T_2}=1$ GeV and rapidities $y_1=0,4$ and $y_2=0$.