First MonteCarlo Global QCD Analysis of Pion Parton Distributions.

P C Barry,Chueng-Ryong Ji,W Melnitchouk,N Sato

doi:10.1103/physrevlett.121.152001

Abstract

We perform the first global QCD analysis of parton distribution functions (PDFs) in the pion, combining πA Drell-Yan data with leading neutron electroproduction from HERA within a MonteCarlo approach based on nested sampling. Inclusion of the HERA data allows the pion PDFs to be determined down to much lower values of x, with relatively weak model dependence from uncertainties in the chiral splitting function. The combined analysis reveals that gluons carry a significantly higher pion momentum fraction, ∼30%, than that inferred from Drell-Yan data alone, with sea quarks carrying a somewhat smaller fraction, ∼15%, at the input scale. Within the same effective theory framework, the chiral splitting function and pion PDFs can be used to describe the d[over ¯]-u[over ¯] asymmetry in the proton.

Highlights

We perform the first global QCD analysis of parton distribution functions (PDFs) in the pion, combining πA Drell-Yan data with leading neutron electroproduction from HERA within a Monte Carlo approach based on nested sampling
The combined analysis reveals that gluons carry a significantly higher pion momentum fraction, ∼30%, than that inferred from Drell-Yan data alone, with sea quarks carrying a somewhat smaller fraction, ∼15%, at the input scale
Leading neutron (LN) electroproduction from HERA [13,14], which at forward angles is expected to be dominated by pion exchange, has been used to study the pion structure function down to very low values of xπ ∼ 10−3

Summary

First Monte Carlo Global QCD Analysis of Pion Parton Distributions

We perform the first global QCD analysis of parton distribution functions (PDFs) in the pion, combining πA Drell-Yan data with leading neutron electroproduction from HERA within a Monte Carlo approach based on nested sampling. Most information on the partonic structure of pions has come from pion-nucleus scattering with prompt photon or dilepton production at CERN [3,4] and Fermilab [5] These data have been used in several QCD analyses [6,7,8,9,10,11,12] to fit the momentum dependence of the pion’s parton distribution functions (PDFs) for parton fractions xπ ≳ 0.1 of the pion’s light-cone momentum.

Published by the American Physical Society

Findings

Cross with