Sally Stefkova (KIT)

Evidence for a rare B decay with two invisible neutrinos at Belle II

Abstract: The decay of B+->K+nunubar is mediated by flavor-changing neutral current. In the Standard Model, the rate for this elusive process is predicted to be 6x10−5, while enhancements are foreseen in many New Physics scenarios. Searching for B+->K+nunubar decays is, however, experimentally challenging as these decays are not only rare but also contain two neutrinos, leaving no signature in the detector. In this seminar, I will show you details of the newest measurement of the rate of B+->K+nunubar decays, which is based on 362 fb-1 of SuperKEKB electron-positron collision data collected at the Upsilon(4S) resonance by the Belle II experiment in Tsukuba, Japan. Using two different reconstruction techniques, we found, for the first time, evidence for the B+->K+nunubar process. At the end of my seminar, I will also highlight future opportunities in B-decays with invisible signatures.