LHCb CollaborationAdeva Andany, BernardoDosil Suárez, ÁlvaroFernández Albor, Víctor ManuelGallas Torreira, Abraham AntonioGarcía Pardiñas, JuliánHernando Morata, José ÁngelPlo Casasus, MáximoRomero Vidal, AntonioSaborido Silva, Juan JoséSanmartín Sedes, BraisSantamarina Ríos, CibránVázquez Regueiro, PabloVázquez Sierra, CarlosVieites Díaz, María2020-05-042020-05-042015Aaij, R., Adeva, B., Adinolfi, M. et al. First observation and measurement of the branching fraction for the decay B 0s → D ∗s ∓ K ± . J. High Energ. Phys. 2015, 130 (2015). https://doi.org/10.1007/JHEP06(2015)1301029-8479http://hdl.handle.net/10347/21986The first observation of the B 0s → D ∗s ∓ K ± decay is reported using 3.0 fb−1 of proton-proton collision data collected by the LHCb experiment. The D ∗s ∓ mesons are reconstructed through the decay chain D ∗s ∓ → γD ∓s(K ∓ K ± π ∓). The branching fraction relative to that for B 0s → D ∗s − π + decays is measured to be B(B0s→D∗s∓K±)/B(B0s→D∗s−π+)=0.068±0.005+0.003−0.002, where the first uncertainty is statistical and the second is systematic. Using a recent measurement of B(B0s→D∗s−π+), the absolute branching fraction of B 0s → D ∗s ∓ K ± is measured as B(B0s→D∗s∓K±)=(16.3±1.2(stat)+0.7−0.5(syst)±4.8(norm))×10−5, where the third uncertainty is due to the uncertainty on the branching fraction of the normalisation channel.eng© CERN, for the benefit of the LHCb Collaboration. Article funded by SCOAP3. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0), which permits use, duplication, adaptation, distribution, and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.https://creativecommons.org/licenses/by/4.0Branching fractionB physicsFlavor physicsHadron-Hadron Scatteringjournal articlehttps://doi.org/10.1007/JHEP06(2015)130open access