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Register a new userSimultaneous extractions of $|V_{ub}|$ and $|V_{cb}|$ with only the exclusive $Lambda_b$ decays
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We perform the simultaneous $|V_{ub}|$ and $|V_{cb}|$ extractions with only the exclusive $Lambda_b$ decays of $Lambda_bto (p,Lambda_c^+)mubar u_mu$, $Lambda_bto ppi^-$ and $Lambda_bto Lambda_c^+ (pi^-, D^-)$. We obtain that $|V_{ub}|=(3.7pm 0.3)times 10^{-3}$ and $|V_{cb}|=(45.9pm 2.7)times 10^{-3}$. Our value of $|V_{ub}|$ is larger than that of $(3.27pm 0.15pm 0.16pm 0.06)times 10^{-3}$, previously extracted by the LHC Collaboration from the exclusive $Lambda_b$ decays also, but nearly identical to $(3.72pm 0.19)times 10^{-3}$ from the exclusive $B$ decays. On the other hand, our extracted result of $|V_{cb}|$ favors the value of $(42.2pm 0.8)times 10^{-3}$ from the inclusive $B$ decays.
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A new framework of heavy quark effective field theory (HQEFT) is studied and compared with the usual heavy quark effective theory (HQET). $|V_{ub}|$, $|V_{cb}|$ and heavy meson decay constants are extracted in the new framework. HQEFT can yield reasonable results for both exclusive and inclusive decays.
We discuss the impact of the recent untagged analysis of ${B}^0rightarrow D^{*}lbar{ u}_l$ decays by the Belle Collaboration on the extraction of the CKM element $|V_{cb}|$ and provide updated SM predictions for the $bto ctau u$ observables $R(D^*)$, $P_tau$, and $F_L^{D^*}$. The value of $|V_{cb}|$ that we find is about $2sigma$ from the one from inclusive semileptonic $B$ decays, and is very sensitive to the slope of the form factor at zero recoil which should soon become available from lattice calculations.
We present a lattice quantum chromodynamics determination of the ratio of the scalar and vector form factors for two semileptonic decays of the $B_s$ meson: $B_s rightarrow K ell u$ and $B_s rightarrow D_s ell u$. In conjunction with future experimental data, our results for these correlated form factors will provide a new method to extract $|V_{ub}/V_{cb}|$, which may elucidate the current tension between exclusive and inclusive determinations of these Cabibbo-Kobayashi-Maskawa mixing matrix parameters. In addition to the form factor results, we determine the ratio of the differential decay rates, and forward-backward and polarization asymmetries, for the two decays.
We summarize the current status of the determination of the CKM matrix elements |V_ud| and |V_us|, which is at the precision frontier of CKM phenomenology. We also review recent progress on the study of charm (semi)leptonic decays, and the determination of |V_cd| and |V_cs|.
In this addendum to $B_s$ mixing observables and $|V_{td}/V_{ts}|$ from sum rules cite{King:2019lal} we study the impact of the recent improvements in the theoretical precision of $B$ meson mixing onto CKM unitarity fits. Our key results are the most precise determination of the angle $gamma = left(63.4pm0.9right)^circ$ in the unitarity triangle and a new value for the CKM element $|V_{cb}|=(41.6pm0.7)cdot10^{-3}$.
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