A long standing discrepancy between the results of exclusive and inclusive measurements of the CKM matrix element |Vub| exists. The charmless semileptonic decay B → πlν̄ is one of the most accessible and powerful channels for determining |Vub| in exclusive modes at e+ e− B-factories. Using data from the Belle II experiment, a new precision measurement of |Vub| becomes possible. In preparation for first precision measurements, an untagged measurement method for extracting B → πlν̄ events is developed. Lepton and pion candidates are combined to form B → πlν̄ candidates. In order to increase the purity, a series of selections is imposed to suppress continuum and other backgrounds. Signal is extracted from a fit to the two-dimensional ∆E and Mbc distribution in bins of the momentum transfer squared of the B-meson to the pion final state. A simultaneous form factor fit to the measured partial branching fractions and lattice QCD input is carried out to determine values of |Vub|.
|I read the instructions||Yes|