Speaker
Description
The $b\rightarrow sll$ ($l=e, \mu$) transition is a flavour-changing neutral current process that mediates through one-loop penguin or box diagrams. The decay is considered to be a good probe for the New Physics as particles predicted in the beyond Standard Model theories can enter into the loop. The exclusive decay $B\rightarrow K^{(*)}l^{+} l^{-}$ was first observed by the Belle experiment, and it provides many observables such as the branching fraction, $CP$ asymmetry and forward-backward asymmetry and other angular observables. Recently, the LHCb experiment has reported some clue of a lepton universality violation from the branching fraction ratio of the $B\rightarrow K\mu^{+}\mu^{-}$ and $B\rightarrow Ke^{+}e^{-}$ decays. In this presentation, we report the status of the analysis of the $B\rightarrow Kl^{+} l^{-}$ decay at the Belle II experiment which started the data taking in 2019. We also present an activity at the Belle II Chulalongkorn University group where we study the $B\rightarrow KJ/\psi$ decay that has the same topology as the $B\rightarrow Kl^{+}l^{-}$.
