New limits on intrinsic charm in the nucleon from global analysis of parton distributions

TL;DR

This paper performs a comprehensive global analysis of parton distribution functions to set new, more stringent limits on the possible intrinsic charm component in the nucleon, utilizing extensive high-energy scattering data.

Contribution

It introduces a refined global QCD analysis incorporating a broader data set to better constrain the intrinsic charm content in the nucleon, with improved upper limits.

Findings

Intrinsic charm momentum fraction at most 0.5% at 4-sigma level

Expanded data set tightens constraints on intrinsic charm

Older EMC data suggest nonzero intrinsic charm but with large uncertainties

Abstract

We present a new global QCD analysis of parton distribution functions, allowing for possible intrinsic charm (IC) contributions in the nucleon inspired by light-front models. The analysis makes use of the full range of available high-energy scattering data for Q^2 > 1 GeV^2 and W^2 > 3.5 GeV^2, including fixed-target proton and deuteron cross sections at lower energies that were excluded in previous global analyses. The expanded data set places more stringent constraints on the momentum carried by IC, with <x>_IC at most 0.5% (corresponding to an IC normalization of ~ 1%) at the 4-sigma level for Delta chi^2 = 1. We also critically assess the impact of older EMC measurements of F_2c at large x, which favor a nonzero IC, but with very large chi^2 values.