Semileptonic $B$ Meson Decays Into A Highly Excited Charmed Meson Doublet

摘要

We study the heavy quark effective theory prediction for semileptonic $B$decays into an orbital excited $F$-wave charmed doublet, the ($2^{+}$, $3^{+}$)states ($D^{*'}_{2}$, $D_{3}$), at the leading order of heavy quark expansion.The corresponding universal form factor is estimated by using the QCD sum rulemethod. The decay rates we predict are $\Gamma_{B\toD^{*'}_{2}\ell\overline{\nu}}=1.85\times10^{-19} {GeV}$ and $\Gamma_{B\toD_{3}\ell\overline{\nu}}=1.78\times10^{-19} {GeV}$. The branching ratios are$\mathcal {B}(B\to D_{2}^{*'}\ell\overline{\nu})=4.6\times10^{-7}$ and$\mathcal {B}(B\to D_{3}\ell\overline{\nu})=4.4\times10^{-7}$, respectively.