Charge Symmetry Violation Quark Distributions via Precise Measurement of π+/π− Ratios in Semi-inclusive Deep Inelastic Scattering

Abstract

Charge symmetry in the nucleon parton distributions assumes the distribution of quarks in the proton are related to those in the neutron. Indirect experimental evidence constrains Charge Symmetry Violation (CSV) to be less than 9%. In Quantum Chromo-Dynamics (QCD), charge symmetry is broken by the mass difference between the up and down quarks. CSV in the valence region can be extracted from precision measurements of the cross section ratio of charged pion production in semi-inclusive deep inelastic scattering (SIDIS) from deuterium. Such measurements were proposed and carried in experiment E12-09-002 at Jefferson Lab. The experiment was conducted in Hall C from fall 2018 to spring 2019 using the upgraded 10.6 GeV incident electron beam. In this SIDIS experiment, charged pions are detected in coincidence with scattered electrons covering the four-momentum transfer of the virtual photon Q^2 from 4 to 5.5 GeV^2, the Bjorken variable x for 0.35-0.65, and the fraction of energy transfer carried by the outgoing pion z from 0.4-0.7.