LHCb CollaborationAdeva Andany, BernardoÁlvarez Cartelle, PaulaDosil Suárez, ÁlvaroFernández Albor, Víctor ManuelGallas Torreira, Abraham AntonioGarcía Pardiñas, JuliánHernando Morata, José ÁngelPazos Álvarez, AntonioPérez Trigo, EliseoPlo Casasus, MáximoRodríguez Pérez, PabloRomero Vidal, AntonioVázquez Regueiro, PabloVázquez Sierra, Carlos2020-05-042020-05-042014Aaij, R., Adeva, B., Adinolfi, M. et al. First observations of the rare decays B + → K + π + π − μ + μ − and B +→ ϕK + μ + μ − . J. High Energ. Phys. 2014, 64 (2014). https://doi.org/10.1007/JHEP10(2014)0641029-8479http://hdl.handle.net/10347/21987First observations of the rare decays B + → K + π + π − μ + μ − and B +→ ϕK +μ+μ− are presented using data corresponding to an integrated luminosity of 3.0 fb−1, collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The branching fractions of the decays are B(B+→K+π+π−μ+μ−)=(4.36−0.29−0.27(stat)±0.21 (syst)±0.18(norm))×10−7,B(B+→ϕK+μ+μ−)=(0.82−0.19−0.17(stat)−0.10−0.04(syst)±0.27(norm))×10−7, where the uncertainties are statistical, systematic, and due to the uncertainty on the branching fractions of the normalisation modes. A measurement of the differential branching fraction in bins of the invariant mass squared of the dimuon system is also presented for the decay B + → K + π + π − μ + μ −.eng© CERN, for the benefit of the LHCb Collaboration. Article funded by SCOAP3. Open Access. 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 madehttps://creativecommons.org/licenses/by/4.0Rare decayHadron-Hadron ScatteringB physicsFlavor physicsjournal article10.1007/JHEP10(2014)064open access