Time-dependent CP violation in b → s γ transitions at Belle II

Sumitted to PubDB: 2019-08-13

Category: Talk, Visibility: Public

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Authors Olga Werbycka
Date 2019-07-02
Belle II Number BELLE2-TALK-CONF-2019-091
Abstract Some physics scenarios beyond the Standard Model of particle physics restore right-handed weak currents, which would manifest themselves in the polarization of the photon produced in bsγ transitions. Due to the VA structure of the quark-W coupling in the Standard Model, this polarization is strongly correlated with the flavour of the b-quark and suppresses interference responsible for time-dependent CP violation in BKresγ decays. Observing sizable values of time-dependent asymmetries in these decays would therefore represent a null-test of the Standard Model. The Belle II experiment at the SuperKEKB energy-asymmetric e+e collider is a substantial upgrade of the B factory facility at the Japanese KEK laboratory. The design luminosity of the machine is 8×1035 cm2s1 and the Belle II experiment aims to record 50 ab1 of data, a factor of 50 more than its predecessor. From February to July 2018, the machine has completed a commissioning run, achieved a peak luminosity of 5.5×1033 cm2s1, and Belle II has recorded a data sample of about 0.5 fb1. Main operation of SuperKEKB has started in March 2019. In this presentation we show how the final Belle II data set will allow to evaluate the time-dependent asymmetries for the final states KS0π0γ and KS0π+πγwithstatisticaluncertaintiesatthelevelofafew10^{-2}$. As a preparatory exercise, we describe the first measurement of the B-lifetime with the early Belle II data, which already allows to understand accurate modelling of the time resolution as an essential ingredient.
Conference PASCOS 2019

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