D* polarization as a probe to discriminate new physics in B¯→D*τν¯

The confirmation of excess in RD∗ at the LHCb is an indication of lepton flavor nonuniversality. Various different new physics operators and their coupling strengths, which provide a good fit to RD, RD∗, and q2 spectra, were identified previously. In this work, we try to find angular observables in B→D∗τν which enable us to distinguish between these new physics operators. We find that the D∗ polarization fraction fL(q2) is a good discriminant of scalar and tensor new physics operators. The change in fL(q2) induced by scalar and tensor operators, is about 3 times larger than the expected uncertainty in the upcoming Belle measurement.