Measurement of Azimuthal Asymmetries in Inclusive Production of Hadron Pairs in e+e- Annihilation at \sqrt{s} = 10.58 GeV

TL;DR

This paper reports the measurement of azimuthal asymmetries in charged pion pairs produced in e+e- annihilation at 10.58 GeV, providing insights into the Collins effect and quark transverse spin fragmentation.

Contribution

It presents a significantly improved measurement of azimuthal asymmetries related to the Collins effect using a large dataset and two reconstruction methods.

Findings

Significant azimuthal asymmetries observed in charged pion pairs.

Results consistent with the Collins effect due to quark transverse spin.

Enhanced statistical precision over previous measurements.

Abstract

The Collins effect connects transverse quark spin with a measurable azimuthal asymmetry in the yield of hadronic fragments around the quark's momentum vector. Using two different reconstruction methods we measure statistically significant azimuthal asymmetries for charged pion pairs in e+e- annihilation at center-of-mass energies of 10.52 GeV and 10.58 GeV, which can be attributed to the fragmentation of primordial quarks with transverse spin components. The measurement was performed using a dataset of 547 fb^{-1} collected by the Belle detector at KEKB improving the statistics of the previously published results by nearly a factor of 20.