First observation of the decay B0s→K−μ+νμ and measurement of |Vub|/|Vcb|

Physical Review Letters. 2021. Vol. 126. No. 8. Article 081804.

Aaij R., Beteta C. A., Arzymatov K., Belavin V., Boldyrev A., Borisyak M., Derkach D., T. Gaintseva, M. Hushchyn, Kazeev N., Maevskiy A., A. Philippov, S. Popov, Ratnikov F., Ryzhikov A., Ustyuzhanin A.

The first observation of the suppressed semileptonic B0s→K−μ+νμ 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(B0s→K−μ+νμ) 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 B0s→D−sμ+νμ, 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 B0s→K− and B0s→D−s transitions are employed to determine the ratio of the Cabibbo-Kobayashi-Maskawa matrix elements |Vub|/|Vcb| at low and high B0s→K− momentum transfer.

Keywords: HEP LHC Standard Model, стандартная модель, БАК, тяжелые кварки

Publication based on the results of: Machine learning to check and improve the quality of data collected at the Large Hadron Collider and other particle physics experiments (2021)