Wednesday, October 23 2019
14:00 - 15:15

Alladi Ramakrishnan Hall

A global fit to charged current B anomalies

Suman Kumbhakar

IIT Bombay

Over the last few years, several measurements in B meson decays, reported by LHCb and
B-factories, show significant deviations from the Standard Model (SM) predictions. These deviations can be considered as possible hint of physics beyond SM. One such class of transitions is induced by b → c l ν quark level decay. This is particularly intriguing because it occurs at tree level within SM. The present world averages of flavour ratios RD and RD∗ are 3.1σ away from the SM predictions. These ratios hint towards lepton flavour universality violation. These measurements indicate that the mechanism of b → c τ ν decay is not identical to that of b → c {e/μ} ν decay. Assuming new physics in b → c τ ν decay, we have done a global fit to the available data to obtain the new physics Wilson coefficients of each new physics four-fermion operator of a given Lorentz structure. We have also shown that it is possible to
distinguish between the new physics solutions by means of the angular observables in B → D/D∗ τ ν ̄decays. In particular, the D∗ polarization fraction is a good discriminant of scalar and tensor new physics operators. We show that very recent measurement of this quantity by the Belle collaboration completely rules out the tensor new physics solution at the level of ∼ 5σ.

1. A. K. Alok, D. Kumar, S. Kumbhakar and S. Uma Sankar, [arXiv: 1903.10486 [hep-ph]]
2. A. K. Alok, D. Kumar, J. Kumar, S. Kumbhakar, S. Uma Sankar; JHEP 1809 (2018) 152
3. A. K. Alok, D. Kumar, S. Kumbhakar and S. Uma Sankar; Phys. Rev. D 95, no. 11, 115038 (2017)

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