Study of Collins Asymmetries at BaBar

TL;DR

This paper reports preliminary measurements of Collins asymmetries in electron-positron collisions, providing insights into the transversity distribution of quarks inside nucleons, using data from the BABAR experiment at 10.54 GeV.

Contribution

It presents the first measurement of azimuthal asymmetries related to the Collins function at BABAR, comparing results with Belle to enhance understanding of nucleon structure.

Findings

Preliminary Collins asymmetry measurements from BABAR data.

Comparison of BABAR results with Belle measurements.

Insights into quark transversity distribution.

Abstract

Transversity distribution describes the quark transverse polarization inside a transversely polarized nucleon. It is the less known leading-twist piece of the QCD description of the partonic structure of the nucleon. Transversity can be extracted from semi-inclusive deep inelastic scattering (SIDIS) where, however, it couples to a new, unknown fragmentation function, called Collins function. We present the preliminary results of the measurement of the azimuthal asymmetries in the process e^+e^- -> qqbar -> pi pi X, where the two pions are produced in opposite hemispheres. These preliminary results are based on a data sample of about 45 fb^{-1}, collected by the BABAR experiment at a center-of-mass energy of 10.54 GeV, and are compared with the Belle measurements.