Consistency check of charged hadron multiplicities and fragmentation functions in SIDIS

TL;DR

This paper derives conditions on fragmentation functions in SIDIS using HERMES data, finds that only certain models satisfy these conditions, and shows discrepancies between data and common PDFs.

Contribution

It introduces new consistency conditions for fragmentation functions in SIDIS and evaluates their compatibility with existing models and PDFs.

Findings

Only the nonlocal chiral-quark model satisfies the derived conditions.

Significant differences in strange and nonstrange PDFs are observed.

HERMES data is incompatible with CTEQ6M and NNPDF3.0 PDFs.

Abstract

We derived the conditions on certain combinations of integrals of the fragmentation functions of pion using HERMES data of the sum for the charged pion multiplicities from semi-inclusive deep-inelastic scattering (SIDIS) off the deuteron target. In our derivation the nucleon parton distribution functions (PDFs) are assumed to be isospin SU(2) symmetric. Similar conditions have also been obtained for the fragmentation functions (FFs) of kaon by the sum of charged kaon multiplicities as well. We have chosen several FFs to study the impact of those conditions we have derived. Among those FFs, only that produced in the nonlocal chiral-quark model (NL$\chi$QM) constantly satisfy the conditions. Furthermore, the ratios of the strange PDFs $S(x)$ and the nonstrange PDFs $Q(x,Q^2)$ extracted from the charged pion and kaon multiplicities differ from each other significantly. Finally, we demonstrate that the HERMES pion multiplicity data is unlikely to be compatible with the two widely-used PDFs, namely CTEQ6M and NNPDF3.0.