Vladimir Chekelian

27 January 2020

Abstract: The Belle~II experiment at the SuperKEKB energy-asymmetric $e^+ e^-$ collider started the first physics run in March 2019 at a center of mass energy corresponding to the mass of the $\Upsilon(4S)$. A first look at the time-dependent $CP$ violation is presented, utilising an early data set comprising 2.6 fb$^{-1}$ of total luminosity. A new concept of time-dependent fits based on a weighting technique applied to an {\it assistive} MC sample of events is presented as well.

Keyword(s): CP violation ; B0-B0bar mixing ; B0 lifetime ; time-dependent analysis ; weighting technique