Sum rules for the T-odd fragmentation functions

TL;DR

This paper derives sum rules for T-odd fragmentation functions based on transverse momentum conservation, explaining observed azimuthal asymmetries in pion production.

Contribution

It introduces new sum rules for T-odd fragmentation functions that clarify the differences between favored and unfavored functions.

Findings

Sum rules relate T-odd fragmentation functions to transverse momentum conservation.

Enhanced differences between favored and unfavored fragmentation functions.

Potential explanation for azimuthal asymmetries observed by HERMES.

Abstract

The conservation of the intrinsic transverse momentum during parton fragmentation imposes non-trivial constraints on T-odd fragmentation functions. These significantly enhance the differences between the favoured and unfavoured fragmentation functions, which could be relevant to understand the azimuthal asymmetries of charged pion production observed recently by the HERMES collaboration.