Flavor Dependence of Charged Pion Fragmentation Functions

TL;DR

This study measures the flavor dependence of charged pion production in semi-inclusive deep-inelastic scattering, revealing flavor-dependent fragmentation functions that tend to unify at low x or high W, indicating possible charge symmetry violation.

Contribution

It provides the first detailed measurement of flavor-dependent pion fragmentation functions in SIDIS, highlighting their convergence at specific kinematic regions.

Findings

Flavor-dependent fragmentation functions are observed.

Functions converge to a common value at low x or high W.

Results suggest possible charge symmetry violation in fragmentation.

Abstract

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 to explore a possible charge symmetry violation in fragmentation functions. The experiment used an electron beam with energies of 10.2 and 10.6 GeV at Jefferson Lab and the Hall-C spectrometers. The electron kinematics spanned the range 0.3<x<0.6, 2<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 transverse momentum range was 0<p_T<0.25 GeV/c. Assuming factorization at low p_T and allowing for isospin breaking, we find that the results can be described by two "favored" and two "un-favored" effective low $p_T$ fragmentation functions that are flavor-dependent. However, they converge to a common flavor-independent value at the lowest x or highest W of this experiment.