Constraints on a new light spin-one particle from rare b→s transitions

The anomalously large like-sign dimuon charge asymmetry in semileptonic b-hadron decays recently measured by the D0 Collaboration may be hinting at the presence of CP-violating new physics in the mixing of Bs mesons. It has been suggested that the effect of a nonstandard spin-1 particle lighter than the b quark with flavor-changing couplings to b and s quarks can reproduce the D0 result within its one-sigma range. Here we explore the possibility that the new particle also couples to charged leptons l=e,μ and thus contributes to rare b→s processes involving the leptons. We consider in particular constraints on its couplings from existing experimental data on the inclusive B→Xsl+l- and exclusive B→K(*)l+l- decays, as well as the anomalous magnetic moments of the leptons. We find that there is parameter space of the particle that is allowed by the current data. We discuss how future measurements of these B transitions and the rare decays of the Bs meson, such as Bs→(φ,η,η')l+l- and Bs→l+l-, at LHCb and next-generation B factories may probe its presence or couplings more stringently.