Semileptonic B and $$B_s$$Bs decays involving scalar and axial-vector mesons

We report our theoretical calculations on the branching fractions for the semileptonic B and $$B_s$$Bs decays based on the form factors in the covariant light-front quark model. That is, $$B (B_s) \rightarrow (P,\, V,\, S,\,A) \ell \nu _\ell $$B(Bs)→(P,V,S,A)ℓνℓ, where P and V denote the pseudoscalar and vector mesons, respectively, while S denotes the scalar meson with mass above 1 GeV and A the axial-vector meson. The branching fractions for the semileptonic $$B\rightarrow P$$B→P and V modes have been measured very well in experiment and our theoretical values are in good agreement with them. The ones for $$B\rightarrow S$$B→S and A modes are our theoretical predictions. There is little experimental information on the semileptonic $$B_s$$Bs decays although much theoretical effort has been done. In addition, we predict the branching fractions of $$B\rightarrow D^*_0(2400) \ell \bar{\nu }_\ell $$B→D0∗(2400)ℓν¯ℓ and $$B_s\rightarrow D^{*-}_{s0}(2317) \ell \bar{\nu }_\ell $$Bs→Ds0∗-(2317)ℓν¯ℓ as $$(2.31\pm 0.25)\times 10^{-3}$$(2.31±0.25)×10-3 and $$(3.07\pm 0.34)\times 10^{-3}$$(3.07±0.34)×10-3, in order, assuming them as the conventional mesons with quark-antiquark configuration. The high luminosity $$e^+e^-$$e+e- collider SuperKEKB/Belle-II is running, with the data sample enhanced by a factor of 40 compared to Belle, which will provide huge opportunity for the test of the theoretical predictions and further help understand the inner structure of these scalar and axial-vector mesons, e.g., the glueball content of $$f_0(1710)$$f0(1710) and the mixing angles for the axial-vector mesons. These decay channels can also be accessed by the LHCb experiment.