EPS09s and EKS98s: Impact parameter dependent nPDF sets

TL;DR

This paper introduces spatially dependent nuclear parton distribution functions (nPDFs), EPS09s and EKS98s, enabling consistent calculation of hard-process cross-sections across different collision centralities at LHC and RHIC.

Contribution

The paper presents the first spatially dependent nPDF sets, EPS09s and EKS98s, derived from global fits and nuclear thickness functions, allowing for centrality-dependent cross-section predictions.

Findings

Predictions for nuclear modification factors in various centrality classes.

Application to neutral pion production in p+Pb collisions at LHC.

Application to prompt photon production in d+Au collisions at RHIC.

Abstract

In our recent study we have determined two new spatially dependent nuclear PDF (nPDF) sets, EPS09s and EKS98s. With these, the hard-process cross-sections can be calculated in different centrality classes consistently with the globally analyzed nPDFs for the first time. The sets were determined by exploiting the $A$-systematics of the globally fitted nPDF sets, EPS09 and EKS98. For the spatial dependence of the nPDFs we used a power series ansatz in the nuclear thickness function $T_A$. In this flash talk we introduce the framework, and present our NLO EPS09s-based predictions for the nuclear modification factor in four centrality classes for inclusive neutral pion production in p+Pb collisions at the LHC and for inclusive prompt photon production in d+Au collisions at RHIC at midrapidity.