Pade approximants to B → πlνl and Bs → Klνl and determination of |Vub|

In light of the first observation of the semileptonic decay B-s(0) -> K-mu(+)nu(mu) by the LHCb Collaboration, we revisit the determination of the Cabibbo-Kobayashi-Maskawa parameter vertical bar V-ub vertical bar from exclusive semileptonic B-meson decays. A controlled theoretical input on the Standard Model B -> pi and B-s -> K vector and scalar form factors from Lattice QCD in the large q(2) region, in combination with experimental measurements of the differential B -> pi l nu(l) and B-s(0) -> K-mu(+)nu(mu) branching ratio distributions, has allowed us determine vertical bar V-ub vertical bar = 3.86(11) x 10(-3) and vertical bar V-ub vertical bar = 3.58(9) x 10(-3) from the analyses of the individual decay channels, respectively, and vertical bar V-ub vertical bar = 3.68(5) x 10(-3) from a simultaneous analysis of both decays, which is only a 1.4% error and differs by 1.8 sigma with respect to the value from inclusive determinations vertical bar V-ub vertical bar = 4.25(12)(-14)(+15)(23) x 10(-3). Our results are based on the use of Pade approximants to the participating form factors, highlighting the importance of the decay B-s -> K mu nu(mu) in complementing the traditional B -> pi l nu(l) one in the exclusive determination of IVubI and allowing us to obtain, to the best of our knowledge, the first correlated results for the B -> pi and B-s -> K vector and scalar form factors. We hope that our study strengthens the case for precise measurements of the differential B-s -> Kl nu(l) decay rate with a finer resolution of the q(2) bins, as it would definitely allow achieving more conclusive results for vertical bar V-ub vertical bar.

Automated summary

The determination of the Cabibbo-Kobayashi-Maskawa parameter |V-ub| from exclusive semileptonic B-meson decays was revisited with controlled theoretical input and experimental measurements, resulting in correlated results for the B -> pi and B-s -> K vector and scalar form factors. The study emphasized the importance of the B-s -> K mu nu(mu) decay in complementing the traditional B -> pi l nu(l) one for the exclusive determination of |V-ub|, aiming for more conclusive results with precise measurements.