Study of T-odd Quark Fragmentation Function in $Z^0\to 2$-jet Decay
A. V. Efremov, O. G. Smirnova, L. G. Tkatchev
TL;DR
The paper investigates the T-odd fragmentation function $H_1^\perp$, which drives left–right asymmetries in the fragmentation of transversely polarized quarks, by analyzing DELPHI $Z\to 2$ jet data. Using a detector-corrected azimuthal distribution of leading particles and the quark spin correlation $C_{TT}$ at the $Z^0$ peak, the authors extract the analyzing power $|H_1^\perp/D_1|$, finding a central value around 6% with uncertainties, and a possible larger value under certain angular dependencies. The results indicate a nonzero $H_1^\perp$ and highlight its potential use in measuring nucleon transversity in polarized DIS, while emphasizing the need for more statistics and careful control of systematic effects. Overall, the study provides the first experimental handle on a T-odd fragmentation function and outlines future avenues for exploring spin phenomena in high-energy fragmentation.
Abstract
The first probe of the correlation of the T-odd one-particle fragmentation function responsible for the left--right asymmetry of fragmentation of a transversely polarized quark and an antiquark is done by using the 1991-95 DELPHI data for $Z\to 2$ jet decay. Integrated over the fraction of longitudinal and transversal momenta, this correlation is of 2.5 ppm order, which means order of 7% for the analyzing power. This makes us hope to use certain effects in polarized DIS experiments for transversity measurement.