The LHCb has recently confirmed the 3.5 sigma deviation of the ratio R_{D*} from the Standard Model (SM) expectation which is an indication towards the lepton flavor non-universality. In order to identify the Lorentz structure of new physics responsible for the R_{D*} excess, one requires measurements of angular observables in B -> D* tau nubar. The D* polarization fraction and the lepton forward-backward asymmetry are both capable of discriminating allowed new physics solutions. However, the measurement of forward-backward asymmetry is an extremely difficult task as it requires the reconstruction of tau momentum.
In arXiv:1606.03164 we suggest a method using which the D* polarization fraction can be measured by making use of the same data which measured R_{D*} ! We find that the D* polarization fraction can discriminate half of the present allowed new physics solutions for the R_{D*} excess. We also find that forward-backward asymmetry do not have additional capability to discriminate between new physics operators. Hence such a measurement does not lead to any advantage in distinguishing between allowed new physics models.
Therefore, we hope, our work can lead to the experimental measurement of D* polarization which would be of great value in narrowing down the allowed new physics models.