Abstract
The first observation of the suppressed semileptonic B_{s}^{0}→K^{-}μ^{+}ν_{μ} 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^{-}μ^{+}ν_{μ}) is measured to be [1.06±0.05(stat)±0.08(syst)]×10^{-4}, where the first uncertainty is statistical and the second one represents the combined systematic uncertainties. The decay B_{s}^{0}→D_{s}^{-}μ^{+}ν_{μ}, where D_{s}^{-} is reconstructed in the final state K^{+}K^{-}π^{-}, 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 |V_{ub}|/|V_{cb}| at low and high B_{s}^{0}→K^{-} momentum transfer.
Highlights
The first observation of the suppressed semileptonic B0s → K−μþνμ decay is reported
This Letter reports the first observation of the decay B0s → K−μþνμ, the measurement of its branching fraction and of the ratio jVubj=jVcbj with B0s → D−s μþνμ as a normalization channel [10]
The ratio jVubj=jVcbj is derived in the two q2 regions using calculations of the form factors of the B0s → K− and B0s → D−s transitions based on both light cone sum rule (LCSR) [11,12] and lattice QCD (LQCD)
Summary
The first observation of the suppressed semileptonic B0s → K−μþνμ 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 BðB0s → K−μþνμÞ is measured to be 1⁄21.06 Æ 0.05ðstatÞÆ 0.08ðsystÞ × 10−4, where the first uncertainty is statistical and the second one represents the combined systematic uncertainties. This Letter reports the first observation of the decay B0s → K−μþνμ, the measurement of its branching fraction and of the ratio jVubj=jVcbj with B0s → D−s μþνμ as a normalization channel [10].
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