Effective theory approach to new physics in b→u and b→c leptonic and semileptonic decays

Dutta, R and Bhol, A and Giri, Anjan Kumar (2013) Effective theory approach to new physics in b→u and b→c leptonic and semileptonic decays. Physical Review D, 88 (11). ISSN 1550-7998

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Abstract

Recent measurements of exclusive B-→τ-ν and B0→π+l-ν̄l decays via the b→ulν transition process differ from the standard model expectation and, if they persist in future B experiments, will be a definite hint of the physics beyond the standard model. Similar hints of new physics have been observed in b→c semileptonic transition processes as well. BABAR measures the ratio of branching fractions of B→(D,D*)τν to the corresponding B→(D,D*)lν, where l represents either an electron or a muon, and finds 3.4σ discrepancy with the standard model expectation. In this context, we consider a most general effective Lagrangian for the b→ulν and b→clν transition processes in the presence of new physics and perform a combined analysis of all the b→u and b→c semi-(leptonic) data to explore various new physics operators and their couplings. We consider various new physics scenarios and give predictions for the Bc→τν and B→πτν decay branching fractions. We also study the effect of these new physics parameters on the ratio of the branching ratios of B→πτν to the corresponding B→πlν decays.

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