Nuclear Physics Seminar

Spontaneous Lambda polarization has been observed in unpolarized pp collisions years ago while the precise mechanism behind it remains unknown. It is assumed that the so called polarizing Fragmentation Function(FF) plays a important role in this effect. The polarizing FF is of great interest not only because it is strongly connected to the spin structure of hadrons, but also it is chiral-even and the sign is possible to be unambiguously measured so it provides a unique opportunity to test the universality of the FFs. The large e+e- annihilation data sample collected by the Belle experiment at the KEKB storage ring allows a precision study of the production of transversely polarized hyperons and check our current understanding of the associated QCD dynamics. The measurement of transverse Lambda/anti-Lambda polarization in e+e- annihilation in the inclusive Lambda production processes at Belle will be presented and discussed. The Belle II detector and SuperKEKB, the upgrade of Belle detector and KEKB collider, are being constructed at the KEK laboratory in Tsukuba, Japan. The K-Long and muon system of Belle II, which provides the K-Long and muon identification, consists of an alternating sandwich iron plates and active detector elements located outside of the superconducting solenoid. The Belle KLM based on glass-electrode resistive plate
chambers(RPC) has demonstrated good performance. However, the long dead time of the RPCs during the recovery of the electric field after a discharge significantly reduces the detection efficiency under high backgrounds fluxes. So the endcap RPCs and two inner layers of barrel RPCs will be retired and replaced with scintillators in Belle II. This talk will introduce the Belle-II detector, mainly KLM system and the related offline software, KLM alignment and the current status of cosmic ray test (CRT).