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|Vub| determination and testing of lepton flavour universality in semileptonic Bc → D(∗) decays

In light of prospects for measurements of Bc → D(∗)lν decays in the upcoming Upgrade II of the LHC, we show that by using calculated Bc → D(∗) form factors a competitive extraction of the |Vub | CKM matrix element from the Bc → Dμν decay might be possible. To minimize experimental and theoretical uncertainties we provide the ratio |Vub |/|Vcs| by normalizing the Bc → D(∗)μν to B c→ J/ψμν decay. We also briefly examine the suggestion to extract |Vub|/|Vcs| from the theoretically interesting ratio of Bc → D0eν and Bc → Bs eν decay rates in the zero-recoil limit. With the present average value of |Vcs |, the predicted branching ratios are estimated to be BR(Bc → D0μν ) = (2.4 ± 0.4) · 10−5 and BR(Bc → D∗μν ) = (7 ± 3) · 10−5, and the semileptonic ratios for testing the lepton flavour universality in these Bc decays are Rc(D0) = 0.64 ± 0.05 and Rc(D∗) = 0.55 ± 0.05. We also provide q2 distributions and various angular observables of Bc → D(∗)lν decays.

Heavy Quark Physics ; Nonperturbative Effects

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