The D0 same-charge dimuon asymmetry and possibile new CP violation sources in the $B_s-\bar{B}_s$ system

TL;DR

This paper investigates potential new physics sources for the large CP violation observed in the D0 dimuon asymmetry, analyzing various models and proposing a U(1)' gauge symmetry extension as a plausible explanation.

Contribution

It introduces a U(1)' gauge symmetry model with exotic quarks and scalars that can account for the observed CP violation while satisfying experimental constraints.

Findings

The U(1)' model can produce large CP violation compatible with data.

Extra Z' gauge boson induces flavor-changing neutral currents at tree level.

Model requires heavy exotic quarks and singlet scalars for consistency.

Abstract

Recently, the D0 collaboration reported a large CP violation in the same-sign dimuon charge asymmetry which has the $3.2 \sigma$ deviation from the value estimated in the Standard Model. In this paper, several new physics models are considered: the MSSM, two Higgs doublet model, the recent dodeca model, and a new $Z'$ model. Generally, it is hard to achieve such a large CP violation consistently with other experimental constraints. We find that a scheme with extra non-anomalous U(1)$'$ gauge symmetry is barely consistent. In general, the extra $Z'$ gauge boson induces the flavor changing neutral current interactions at tree level, which is the basic reason allowing a large new physics CP violation. To preserve the U(1)$'$ symmetry at high energy, SU(2)$_L$ singlet exotic heavy quarks of mass above 1 TeV and the Standard Model gauge singlet scalars are introduced.