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

In light of prospects for measurements of Bc → D(∗)lv 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 $$ {B}_c\to D\mu {\overline{v}}_{\mu } $$ decay might be possible. To minimize experimental and theoretical uncertainties we provide the ratio |Vub|/|Vcb| by normalizing the $$ {B}_c\to {D}^{\left(\ast \right)}\mu {\overline{v}}_{\mu } $$ to $$ {B}_c\to J/\psi \mu {\overline{v}}_{\mu } $$ decay. We also briefly examine the suggestion to extract |Vub|/|Vcs| from the theoretically interesting ratio of $$ {B}_c\to {D}^0e{\overline{v}}_e $$ and $$ {B}_c\to {B}_se{\overline{v}}_e $$ decay rates in the zero-recoil limit. With the present average value of |Vub|, the predicted branching ratios are estimated to be $$ BR\left({B}_c\to {D}^0\mu {\overline{\nu}}_{\mu}\right)=\left(2.4\pm 0.4\right)\cdotp {10}^{-5} $$ and $$ BR\left({B}_c\to {D}^{\ast}\mu {\overline{\nu}}_{\mu}\right)=\left(7\pm 3\right)\cdotp {10}^{-5}, $$ 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.