Multiple parton interactions and forward double pion production in pp and dA scattering

TL;DR

This paper investigates how double-parton interactions influence forward double pion production in proton-proton and deuteron-gold collisions at RHIC, revealing their significance at large rapidities and implications for understanding parton distributions.

Contribution

It provides the first estimation of double-parton interaction effects on double pion production in pp and dA collisions, highlighting their role in explaining RHIC data features.

Findings

Double-parton interactions significantly enhance the cross section at large forward rapidities.

These interactions explain the pedestal component in dA collision data.

Shadowing and energy loss effects are more pronounced in double-inclusive than single-inclusive pion production.

Abstract

We estimate the contributions by double-parton interactions to the cross sections for pp->pi^0 pi^0 X and dA->pi^0 pi^0 X at RHIC. We find that such contributions become important at large forward rapidities of the produced pions. This is in particular the case for dA scattering, where they strongly enhance the azimuthal-angular independent "pedestal" component of the cross section, providing a natural explanation of this feature of the RHIC dA data. We argue that the discussed processes open a window to studies of double quark distributions in nucleons. We also briefly address the roles of shadowing and energy loss in dA scattering, which we show to affect the double-inclusive pion cross section much more strongly than the single-inclusive one. We discuss the implications of our results for the interpretation of pion azimuthal correlations.