Determinations of $|V_{cb}|$ and $|V_{ub}|$ from baryonic ${\Lambda }_b$ decays

Abstract

We extract the Cabibbo-Kobayashi-Maskawa matrix element $V_{cb}$ from the exclusive decays of ${\Lambda }_b\to {\Lambda }_c\ell {\bar{\nu }}_{\ell }$ and ${\Lambda }_b\to {\Lambda }_c{M}_{(c)}$ with $M=({\pi }^{-},K^{-})$ and $M_c=(D^{-},D_s^{-})$, where the branching ratios of ${\Lambda }_b\to \Lambda M_{(c)}$ measured with high precisions have not been used in the previous studies. Explicitly, we find $|V_{cb}|=(44.0\pm 3.5)\times 10^{-3}$, which agrees with the value of $(42.11\pm 0.74)\times 10^{-3}$ from the inclusive $B\to X_c\ell {\bar{\nu }}_{\ell }$ decays. Furthermore, based on the most recent ratio of $|V_{ub}|/|V_{cb}|$ from the exclusive ${\Lambda }_b$ decays, we obtain $|V_{ub}|=(4.2\pm 0.4)\times 10^{-3}$, which is close to the value of $(4.49\pm 0.24)\times 10^{-3}$ from the inclusive $B\to X_u\ell {\bar{\nu }}_{\ell }$ decays. We conclude that our determinations of $|V_{cb}|$ and $|V_{ub}|$ from the exclusive ${\Lambda }_b$ decays favor the inclusive extractions in the $B$ decays.

Comments: 8 pages, i figure