Isovector EMC Effect from Global QCD Analysis with MARATHON Data

C Cocuzza,A W Thomas,A Metz,C E Keppel,N Sato,W Melnitchouk,H Liu

doi:10.1103/physrevlett.127.242001

Abstract

We report the results of a MonteCarlo global QCD analysis of unpolarized parton distribution functions (PDFs), including for the first time constraints from ratios of ^{3}He to ^{3}H structure functions recently obtained by the MARATHON experiment at Jefferson Lab. Our simultaneous analysis of nucleon PDFs and nuclear effects in A=2 and A=3 nuclei reveals the first indication for an isovector nuclear EMC effect in light nuclei. We find that while the MARATHON data yield relatively weak constraints on the F_{2}^{n}/F_{2}^{p} neutron to proton structure function ratio and on the d/u PDF ratio, they suggest an enhanced nuclear effect on the d-quark PDF in the bound proton, questioning the assumptions commonly made in nuclear PDF analyses.

Highlights

We report the results of a Monte Carlo global QCD analysis of unpolarized parton distribution functions (PDFs), including for the first time constraints from ratios of 3He to 3H structure functions recently obtained by the MARATHON experiment at Jefferson Lab
Our simultaneous analysis of nucleon PDFs and nuclear effects in A 1⁄4 2 and A 1⁄4 3 nuclei reveals the first indication for an isovector nuclear European Muon Collaboration (EMC) effect in light nuclei
We find that while the MARATHON data yield relatively weak constraints on the Fn2=Fp2 neutron to proton structure function ratio and on the d=u PDF ratio, they suggest an enhanced nuclear effect on the d-quark PDF in the bound proton, questioning the assumptions commonly made in nuclear PDF analyses

Summary

Isovector EMC Effect from Global QCD Analysis with MARATHON Data

Introduction.—The quest to unravel the three-dimensional structure of the nucleon has recently taken on new impetus with the development of experimental programs at modern accelerator facilities at CEBAF at Jefferson Lab, RHIC at BNL, and COMPASS at CERN aimed at studying processes sensitive to transverse momentum dependent distributions and generalized parton distributions. These complement the more traditional observables, such as from lepton-nucleon deep-inelastic scattering (DIS), that provide information on the one-dimensional structure encoded in parton distribution functions (PDFs). In the MARATHON analysis [14], the model calculation of Kulagin and Petti (KP) [15] was used to extract Fn2=Fp2

Published by the American Physical Society

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