Neutral gauge boson contributions to the dimuon charge asymmetry in B decays

Recently, the DØ Collaboration measured the CP-violating like-sign dimuon charge asymmetry in neutral B decays, finding a 3.2σ difference from the standard-model (SM) prediction. Anon-SM charge asymmetry asls suggests a new-physics (NP) contribution to \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$ {B_s} - {\bar{B}_s} $\end{document} mixing. In this case, in order to explain the measured value of asls within its 1σ range, NP must be present in Γ12s, the absorptive part of the mixing. In this paper, we examine whether such an explanation is possible in models with flavor-changing Z (ZFCNC) or Z′ (Z′FCNC) gauge bosons. The models must also reproduce the measured values of the indirect CP asymmetry Sψϕ in Bs → J/ψϕ, and ∆Γs, the \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$ {B_s} - {\bar{B}_s} $\end{document} width difference. We find that the ZFCNC model cannot reproduce the present measured values of Sψϕ and asls within their 1σ ranges. On the other hand, in the Z′FCNC model, the values of all three observables can be simultaneously reproduced.