No abstract

Charged current semi-leptonic decays of B-meson are important for a precise determination of the CKM elements. The CKM elements |Vub| and |Vcb| show a discrepancy between the exclusive and inclusive determinations. These determinations are however masked with hadronic and other uncertainties, and thus can’t be unambiguously taken as implying new physics. In the present study, we propose a new observable: the ratio of these two CKM elements, $$ {R}_V\equiv \frac{\left|{V}_{ub}\right|}{\left|{V}_{cb}\right|} $$ R V ≡ V ub V cb , which is found to receive negligible corrections due to hadronic as well as QED effects. Interestingly, RV as constructed from exclusive determinations of |Vub| and |Vcb| agrees quite well with that constructed from the inclusive determinations of these CKM elements. Hence, we propose that RV is a better and cleaner observable, and can serve as an excellent tool for the test of the Standard Model. We also provide an example of its probing power.

In this era of precision, it has become necessary to have precise expressions and construct theoretically clean observables to match with the experiments. The O ( ) QED corrections to → ℓ + ℓ − modes are discussed here. The structure of the contact term is fixed by demanding gauge invariance of the real emission amplitude. A fictitious photon mass ( ) acts as IR regulator, and the results are shown to be independent of it. The QED effects in the individual channel are found to be negative. The electron channel is shown to receive a large correction of O (20%). The impact of soft photons on the lepton flavour universality (LFU) ratio () is also discussed.