Measurement of the phase difference between short- and long-distance amplitudes in the B+→K+μ+μ- decay

Abstract

A measurement of the phase difference between the short- and long-distance contributions to the {{B} ^+} → {{{K}} ^+} {μ ^+μ ^-} decay is performed by analysing the dimuon mass distribution. The analysis is based on pp collision data corresponding to an integrated luminosity of 3 fb^{-1} collected by the LHCb experiment in 2011 and 2012. The long-distance contribution to the {{B} ^+} → {{{K}} ^+} {μ ^+μ ^-} decay is modelled as a sum of relativistic Breit-Wigner amplitudes representing different vector meson resonances decaying to muon pairs, each with their own magnitude and phase. The measured phases of the {{J}/ψ } and ψ {(2S)} resonances are such that the interference with the short-distance component in dimuon mass regions far from their pole masses is small. In addition, constraints are placed on the Wilson coefficients, C9 and C_{10}, and the branching fraction of the short-distance component is measured.