Rare and forbidden B and tau decays in the Belle

Abstract

A search for the purely leptonic decays B+ → e+ve and B+ → μ+vμ was performed using the 772 million BB̄ pairs collected by the Belle detector at the KEKB asymmetric-energy e+e− collider. There was no evidence of a signal in either decay modes. A heavy neutral leptonlike new particle and heavy neutrino searches were also performed, but no significant signals were observed. Lepton flavor violation in τ decays was studied with an almost full data sample and the upper limits obtained were in the order of 10−8. In this paper, recent results that can give any constraints to new physics are briefly described.