Neutral Gauge Boson Contributions to the Dimuon Charge Asymmetry in B Decays

TL;DR

This paper investigates whether models with flavor-changing Z and Z' gauge bosons can explain the observed dimuon charge asymmetry in B decays, finding Z' models can simultaneously fit multiple experimental measurements.

Contribution

It demonstrates that Z' flavor-changing neutral current models can account for the dimuon charge asymmetry and related CP violation measurements, unlike Z models.

Findings

ZFCNC models cannot reproduce all measurements within 1sigma.

Z'FCNC models can simultaneously fit a_sl^s, S_psi-phi, and Delta Gamma_s.

The study constrains new physics contributions to B meson mixing.

Abstract

Recently, the D0 Collaboration measured the CP-violating like-sign dimuon charge asymmetry in neutral B decays, finding a 3.2sigma difference from the standard-model (SM) prediction. A non-SM charge asymmetry a_sl^s suggests a new-physics (NP) contribution to Bs-Bsbar mixing. In this case, in order to explain the measured value of a_sl^s within its 1sigma range, NP must be present in Gamma_12^s, 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 S_psi-phi in Bs -> J/psi phi, and Delta Gamma_s, the Bs-Bsbar width difference. We find that the ZFCNC model cannot reproduce the present measured values of S_psi-phi and a_sl^s within their 1sigma ranges. On the other hand, in the Z'FCNC model, the values of all three observables can be simultaneously reproduced.