Youngmin Yook

01 June 2021
Charm 2020

Abstract: The Belle II experiment has accumulated data corresponding to 89.99 fb-1 integrated luminosity in the past 2 years, and is performing very good. Waiting that the full planned data set will be recorded (50 ab-1), which will allow search for rare processes and will have a tremendous impact in the spectroscopy field, the Phase 3 data set allows to already perform analysis with high precision. We present here the analysis of B -> K J/psi pi pi and B -> K psi(2S): in the former for the first time the evidence for the X(3872) --->Jpsi pi pi has been found at Belle II, which is consistent with the observation at Belle of the same resonant state, performed in 2003. The re-discovery of the X(3872) based on the early Phase3 data includes the efficiency and resolution study, calibration with B -> K psi(2S), and background check. When higher statistics will be available, Belle II is planning the even more interesting analysis of B--->DD*K, and search for X(3872)→DD*.