Constraints on a New Light Spin-One Particle from Rare b -> s Transitions

TL;DR

This paper investigates constraints on a hypothetical light spin-1 particle with flavor-changing couplings to b and s quarks, which could explain anomalies in B_s meson mixing and affect rare B decays involving leptons, using current experimental data.

Contribution

It explores the parameter space of a new light spin-1 particle coupling to leptons and quarks, providing constraints based on existing B decay measurements and lepton magnetic moments.

Findings

Allowed parameter space for the new particle exists within current experimental bounds.

Future B decay measurements can further constrain or detect the particle.

The particle could simultaneously explain B_s mixing anomalies and be consistent with lepton magnetic moments.

Abstract

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 B_s 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,mu 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 -> X_s l^+ 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. Future measurements of these B transitions and rare decays of the B_s meson, such as B_s -> (phi,eta,eta') l^+ l^- and B_s -> l^+ l^-, at LHCb and next-generation B factories can probe its presence or couplings more stringently.