Observation of polarization in e+e- annihilation into a hyperon-antihyperon pair
by
B105
CHEP
Baryon-antibaryon pairs could be produced at electron-positron colliders if sufficient center-of-mass energy is available. The process is strongly enhanced if the energy is tuned to match J/y or y′ resonances. The spin orientations of the produced baryon and antibaryon are entangled and for the spin one-half baryons the system is described by two complex form factors. If the relative phase between the form factors, ΔΦ, is non-zero the produced particles are transversely polarized even if the beams are unpolarized. The polarization could be determined for hyperons from asymmetry of the decay distribution. Recent BESIII result shows that the ΔΦ phase for e+e-→J/y® Λ`Λ is close to 45o. The observed polarization and the spin correlations allow to simultaneously measure decay parameters for Λ and `Λ hyperons. In particular we determine decay parameter a- for Λ→pp- for the first time since 1975. The value is more precise and (17±3)% larger than the world average. Our result greatly enhances prospects for observation of CP violation for strange baryons at Super Tau Charm Factory.
Andrzej Kupsc, is a researcher working in the field experimental light hadron physics. He has obtained PhD at Soltan Institute for Nuclear Studies, Warsaw Poland in 1994 from an experiment at CELSIUS storage ring in Uppsala, Sweden. During postdoctoral fellowship at The Svedberg Laboratory, Uppsala he was responsible for WASA detector electromagnetic calorimeter assembly and tests at The Svedberg Laboratory in Uppsala. Since 1998 he has a permanent position at Uppsala University. Until recently his main research interests were production and decay studies of light neutral pseudoscalar mesons at WASA-at-COSY, KLOE-2 and BESIII experiments. More specifically most of his work has focused on meson transition form factors and dynamics of three body decays. This includes both analysis of the experimental data and the interpretation in collaboration with theory groups. He is physics coordinator for WASA-at-COSY and deputy physics coordinator for KLOE-2. During 2012-2014 he was spokesperson for MesonNet, a European Research Network, and now he is co-spokesperson of EU research initiative “Precision Tests of the Standard Model” (PrecisionSM). The talk will be related to his recent research project concerning exclusive production of a hyperon-antihyperon pair in chamonia decays.
