The Collins function: a simple model calculation

Abstract

The Collins function belongs to the class of the so-called time-reversal odd fragmentation functions. Being chiral-odd as well, it can serve as an important tool to observe the nucleon's transversity distribution in semi-inclusive DIS. Due to the possible presence of final state interactions, this function can be non-zero, though this has never been demonstrated in an explicit model calculation. We use a simple pseudoscalar coupling between pions and quarks to model the fragmentation process and we show that the inclusion of one-loop corrections generates a non-vanishing Collins function, therefore giving support to its existence from the theoretical point of view.

Figures (4)

• Figure 1: Lowest-order unitarity diagram describing the fragmentation of a quark into a pion.
• Figure 2: One-loop corrections to the fragmentation of a quark into a pion.
• Figure 3: One-loop self-energy and vertex corrections.
• Figure 4: Interpretation of the one-loop corrections as final state interaction.