| Seminar Date: | Thursday, July 19, 2012 |
| Time: | 12:30 PM - 1:30 PM |
| Location: | KIPAC Auditorium |
| Abstract: | The polarized fragmentation function, or Collins function, measures how the orientation of the quark spin influences the direction of emission of hadrons in the fragmentation process, and can thus be used as a quark spin analyzer. Furthermore, the Collins function is needed for the extraction of the transversity parton distribution function (PDF) from semi-inclusive deep inelastic scattering data. This PDF describes the quark transverse polarization inside a transversely polarized nucleon, and is the least known leading-twist PDF. Direct information on the Collins function can be obtained from the measurement of azimuthal asymmetries in inclusive processes, such as e^+e^- -> h_1 h_2 X, with the two hadrons belonging to opposite jets. I will present preliminary measurements of Collins asymmetries in the inclusive process e^+e^- -> pi^+- pi^+- X at a center-of-mass energy of 10.6 GeV, using a data sample of 468 fb^(-1) collected by the BaBar experiment. Considering pairs of charged pions produced in opposite hemispheres of hadronic events, I will show asymmetries in the distributions of their azimuthal angles in two distinct reference frames, and discuss their behavior as a function of pion fractional energies, pion transverse momenta, and polar angle of the analysis axes. |
| Speaker: | Isabella Garzia - Universita di Ferrara and SLAC
 Dr. Garzia earned her PhD in March from Ferrara University, with a measurement of Collins asymmetries for charged pion pairs in light-flavor hadronic events at BaBar. She has spent the past 6 months on a fellowship at SLAC completing a much improved measurement, presented today. In August, she will start A postdoc at Ferrara University, with the goal of extending these studies, as well as pursuing other experiments.
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