Measurement of the isospin asymmetry in B -> K-(*)mu(+)mu(-) decays

The isospin asymmetries of B -> K-(*)mu(+)mu(-) decays and the partial branching fractions of B-0 -> K-0 mu(+)mu(-) and B+ -> K*+mu(+)mu(-) are measured as a function of the di-muon mass squared q(2) using an integrated luminosity of 1.0 fb(-1) collected with the LHCb detector. The B -> K mu(+)mu(-) isospin asymmetry integrated over q(2) is negative, deviating from zero with over 4 sigma significance. The B -> K*mu(+)mu(-) decay measurements are consistent with the Standard Model prediction of negligible isospin asymmetry. The observation of the decay B0 -> K-s(0)mu(+)mu(-) is reported with 5.7 sigma significance. Assuming that the branching fraction of B-0 -> K-0 mu(+)mu(-) is twice that of B-0 -> K-s(0)mu(+)mu(-), the branching fractions of B-0 -> K-0 mu(+)mu(-) and B -> K*(+)mu(+)mu(-) it are found to be (0.31(-0.06)(+0.07)) x 10(-6) and (1.16 +/- 0.19) x 10(-6), respectively. RI Galli, Domenico/A-1606-2012; Sarti, Alessio/I-2833-2012; Coca, Cornelia/B-6015-2012; Petrolini, Alessandro/H-3782-2011; Carbone, Angelo/C-8289-2012; de Paula, Leandro/I-9278-2012; manca, giulia/I-9264-2012; Patrignani, Claudia/C-5223-2009; Marconi, Umberto/J-2263-2012; de Simone, Patrizia/J-3549-2012; Cardini, Alessandro/J-5736-2012; Teodorescu, Eliza/K-3044-2012