First Observation of the Decay Bs0 → K-μ+νμ and a Measurement of |Vub|/|Vcb|

作者：Aaij, R.; Beteta, C. Abellan; Ackernley, T.; Adeva, B.; Adinolfi, M.; Afsharnia, H.; Aidala, C. A.; Aiola, S.; Ajaltouni, Z.; Akar, S.; Albrecht, J.; Alessio, F.; Alexander, M.; Albero, A. Alfonso; Aliouche, Z.; Alkhazov, G.; Cartelle, P. Alvarez; Amato, S.; Amhis, Y.; An, L.; Anderlini, L.; Andreianov, A.; Andreotti, M.; Archilli, F.; Artamonov, A.; Artuso, M.; Arzymatov, K.; Aslanides, E.; Atzeni, M.; Audurier, B.; Bachmann, S.; Bachmayer, M.; Back, J. J.; Baker, S.; Baladron Rodriguez, P.

来源：Physical Review Letters, 2021, 126(8): 081804.

DOI：10.1103/PhysRevLett.126.081804

• CP-VIOLATION

The first observation of the suppressed semileptonic B-s(0) -> K-mu(+)nu(mu) decay is reported. Using a data sample recorded in pp collisions in 2012 with the LHCb detector, corresponding to an integrated luminosity of 2 fb(-1), the branching fraction B(B-s(0) -> K-mu(+)nu(mu)) is measured to be [1.06 +/- 0.05(stat) +/- 0.08(syst)] x 10(-4), where the first uncertainty is statistical and the second one represents the combined systematic uncertainties. The decay B-s(0) -> D-s(-)mu(+)nu(mu), where D-s(-) is reconstructed in the final state K+K-pi(-), is used as a normalization channel to minimize the experimental systematic uncertainty. Theoretical calculations on the form factors of the B-s(0) -> K- and B-s(0) -> D-s(-) transitions are employed to determine the ratio of the Cabibbo-Kobayashi-Maskawa matrix elements vertical bar V-ub vertical bar/vertical bar V-cb vertical bar at low and high B-s(0) -> K- momentum transfer.