A Study of Charge Symmetry Violation in Fragmentation Functions Extracted from Semi-Inclusive Electroproduction of Charged Pions from Protons and Deuterons

We have measured the flavor dependence of multiplicities for $\pi^+$ and $\pi^-$ production in semi-inclusive deep-inelastic scattering (SIDIS) on proton and deuteron targets. We used a 10.6 GeV electron beam at Jefferson Lab, Hall C and 4 msr solid angle spectrometers (HMS for electrons, SHMS for pions), the lepton vertex spanned the kinematic range $0.3<x<0.65$, $3.5<Q^2<5.5$ GeV$^2$, and $4<W^2<11$ GeV$^2$. The pion fractional momentum range was $0.3< z < 0.7$ and the small transverse momentum range was $0<P_t<0.25$ GeV. We used the multiplicities to form sum-and-difference ratios, testing the validity of factorization in the limited $P_t$ range. From the four multiplicities, we have extracted four flavor-dependent fragmentation functions (FFs), two favored and two un-favored, and studied their $W$ and $x$ dependence. We observe a significant charge symmetry violation in the favored FFs at low $W$ (or high $x$). We will briefly summarize our findings in this talk.