Cocuzza CKeppel C.ELiu HMelnitchouk WMetz ANOBUO SATOThomas A.W.2022-04-252022-04-25202100319007https://www.scopus.com/inward/record.uri?eid=2-s2.0-85121648833&doi=10.1103%2fPhysRevLett.127.242001&partnerID=40&md5=ec2bf0b1a962abbb29cfe7988f1e4ae4https://scholars.lib.ntu.edu.tw/handle/123456789/606430We 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 He3 to H3 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 F2n/F2p 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. ? 2021 authors. Published by the American Physical Society.Atomic physicsData yieldsDistribution function effectsIsovectorsLight nucleiNuclear effectsParton distribution functionsProton structureSimultaneous analysisStructure functionsTime constraintsDistribution functionsjournal article10.1103/PhysRevLett.127.242001349517812-s2.0-85121648833