EPS09 - Global NLO analysis of nuclear PDFs and their uncertainties

TL;DR

EPS09 provides a comprehensive NLO global analysis of nuclear PDFs, incorporating new data and detailed error estimation, enabling better uncertainty quantification for nuclear parton distributions.

Contribution

This work introduces the EPS09 NLO nuclear PDFs with an advanced Hessian error analysis, improving constraints on gluon distributions and uncertainty quantification over previous LO analyses.

Findings

Better constrained gluon distributions due to new data inclusion

Detailed Hessian error sets for uncertainty propagation

Enhanced accuracy over previous LO analyses

Abstract

In this talk, we introduce our recently completed next-to-leading order (NLO) global analysis of the nuclear parton distribution functions (nPDFs) called EPS09 - a higher order successor to the well-known leading-order (LO) analysis EKS98 and also to our previous LO work EPS08. As an extension to similar global analyses carried out by other groups, we complement the data from deep inelastic $l+A$ scattering and Drell-Yan dilepton measurements in p+$A$ collisions by inclusive midrapidity pion production data from d+Au collisions at RHIC, which results in better constrained gluon distributions than before. The most important new ingredient, however, is the detailed error analysis, which employs the Hessian method and which allows us to map out the parameter-space vicinity of the best-fit to a collection of nPDF error sets. These error sets provide the end-user a way to compute how the PDF-uncertainties will propagate into the cross sections of his/her interest. The EPS09 package to be released soon, will contain both the NLO and LO results for the best fits and the uncertainty sets.