Decay constants of the $$B_c$$ mesons with vector and tensor currents

Abstract

We calculate the decay constants of the lowest-lying

mesons in the spin-parity channels

$$J^P {=}\,\, 0^-,\,0^+,\,1^-,\,1^+$$ J P = 0 - , 0 + , 1 - , 1 +

, commonly referred to as the

$$B_c,\, B_{c0}^*,\, B_c^*,\, B_{c1}$$ B c , B c 0 ∗ , B c ∗ , B c 1

mesons, respectively. Within the framework of QCD sum rules, we consider the decay constants associated with both the (axial-)vector and (axial-)tensor interpolating currents. The decay constants with (axial-)vector currents have already been studied in the literature. We refine previous QCD sum rule results by including higher-order power corrections and performing a comprehensive uncertainty analysis. Furthermore, we provide the first determination of the (axial-)tensor decay constants of the

$$B_c^*$$ B c ∗

and

$$B_{c1}$$ B c 1

mesons. These new results will not only improve theoretical predictions for purely leptonic

$$B_c$$ B c

decays, but also strengthen unitarity constraints on

$$b \rightarrow c$$ b → c

form factors, thereby improving the precision of predictions for

$$\bar{B} \rightarrow D^{(*)} \ell \bar{\nu }$$ B ¯ → D ( ∗ ) ℓ ν ¯

decays and the determination of

$$|V_{cb}|$$ | V cb |

.