000001612 001__ 1612
000001612 005__ 20190813065918.0
000001612 037__ $$aBELLE2-TALK-CONF-2019-091
000001612 041__ $$aeng
000001612 088__ $$aBELLE2-TALK-DRAFT-2019-079
000001612 100__ $$aOlga Werbycka
000001612 245__ $$aTime-dependent CP violation in b → s γ transitions at Belle II
000001612 260__ $$aPASCOS 2019$$c2019-07-02
000001612 300__ $$amult. p
000001612 500__ $$a20 min
000001612 520__ $$a 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 $b\to s\gamma$ transitions. Due to the $V-A$ 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 $B\to K_{res}\gamma$ 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 $8\times 10^{35}$ cm$^{-2}$s$^{-1}$ and the Belle II experiment aims to record 50 ab$^{-1}$ 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 $5.5\times 10^{33}$ cm$^{-2}$s$^{-1}$, and Belle II has recorded a data sample of about 0.5 fb$^{-1}$. 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 $K_S^0\pi^0\gamma$ and $K_S^0\pi^+\pi^-\gamma with statistical uncertainties at the level of a few $10^{-2}$. 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.
000001612 8560_ $$fdoris.yangsoo.kim@desy.de
000001612 8564_ $$uhttps://docs.belle2.org/record/1612/files/BELLE2-TALK-CONF-2019-091.pdf