Measuring CP violation in b →cτ- ν ̄ τ using excited charm mesons MEASURING CP VIOLATION in ... DANIEL ALONI, YUVAL GROSSMAN, and ABNER SOFFER

There is growing evidence for deviation from the standard model predictions in the ratios between semitauonic and semileptonic B decays, known as the R(D(∗)) puzzle. If the source of this nonuniversality is new physics, it is natural to assume that it also breaks CP symmetry. In this paper we study the possibility of measuring CP violation in semitauonic B decays, exploiting interference between excited charm mesons. Given the current values of R(D(∗)), we find that our proposed CP-violation observable could be as large as about 10%. We discuss the experimental advantages of our method and propose carrying it out at Belle II and LHCb.