First observations of the rare decays B (+) -> K (+)pi (+)pi (-)mu(+)mu (-) and B (+)-> phi K (+)mu(+)mu (-)

Abstract

First 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 −. Keywords: Rare decay, Hadron-Hadron Scattering, B physics, Flavor physi