Semileptonic $B_{(s)}$ meson decays to $D_0^{\ast }(2300),D_{s0}^{\ast }(2317),D_{s1}(2460),D_{s1}(2536),D_1(2420)$ and $D_1(2430)$ within the covariant light-front approach

Abstract

In this work, we investigate the semileptonic decays of $B_{(s)}$ meson to $D_0^{\ast }(2300)$, $D_{s0}^{\ast }(2317)$, $D_{s1}(2460)$, $D_{s1}(2536)$, $D_1(2420)$ and $D_1(2430)$ in the covariant light-front quark model (CLFQM). We combine the helicity amplitudes via the corresponding form factors to obtain the branching ratios of the semileptonic decays $B_{(s)}\to D_{(s)}^{\ast \ast }\ell \hat{I}{½}_{\ell }$ with $D_{(s)}^{\ast \ast }$ referring to a P-wave exicted charmed meson $D_0^{\ast }(2300)$, $D_{s0}^{\ast }(2317)$, $D_{s1}(2460)$, $D_{s1}(2536)$, $D_1(2420)$ or $D_1(2430)$ and $\ell =e,\hat{I}¼,\ddot{I}„$. Furthermore, we also take into account another two physical observables, namely the longitudinal polarization fraction $f_L$ and the forward-backward asymmetry $A_{FB}$. Most of our predictions are comparable to the results given by other theoretical approaches and the present available data. The branching ratios of the semileptonic decay channels $B_s\to D_{s1}(2460)\ell \hat{I}{½}_{\ell }$ and $B\to D_1(2420)\ell \hat{I}{½}_{\ell }$ are larger than those of the semileptonic decays $B_s\to D_{s1}(2536)\ell \hat{I}{½}_{\ell }$ and $B\to D_1(2430)\ell \hat{I}{½}_{\ell }$, respectively. We find that the long-standing '$1/2$ vs $3/2$ puzzle' in the decays $B^{+}\to {\bar{D}}_1^{(\prime )0}{\ell }^{\prime +}\hat{I}{½}_{{\ell }^{\prime }}$ $({\ell }^{\prime }=e,\hat{I}¼)$ can be solved by taking some negative mixing angle $\hat{I}{¸}_s$ values within a range from $-30.3^{\circ }$ to $-24.9^{\circ }$, corresponding to $\hat{I}¸$ of about $5^{\circ }\sim 10.4^{\circ }$. While Belle collaboration updated their measurements for the decays $B^0\to D_0^{\ast -}{\ell }^{\prime +}\hat{I}{½}_{{\ell }^{\prime }}$ with only a small upper limit $Br(B^0\to D_0^{\ast -}{\ell }^{\prime +}\hat{I}{½}_{{\ell }^{\prime }})<0.44\times 10^{-3}$ obtained, which is much larger than most theoretical predictions and causes a new puzzle.

25 pages, 6 figures. arXiv admin note: text overlap with arXiv:2405.00496