Additional Information on Heavy Quark Parameters from Charged Lepton Forward-Backward Asymmetry

Abstract

The determination of $|V_{cb}|$ using inclusive and exclusive (semi-)leptonic decays exhibits a long-standing tension of varying ${\cal O}(3 \sigma)$ significance. For the inclusive determination the decay rate is expanded in $1/m_b$ using heavy quark expansion, and from moments of physical observables the higher order heavy quark parameters are extracted from experimental data in order to assess $|V_{cb}|$ from the normalisation. The drawbacks are high correlations both theoretically as well as experimentally among these observables. We will scrutinise the inclusive determination in order to add a new and less correlated observable. This observable is related to the decay angle of the charged lepton and can help to constrain the important heavy quark parameters in a new way. It may validate the current seemingly stable extraction of $|V_{cb}|$ from inclusive decays or hints to possible issues, and even may be sensitive to New Physics operators.