D0 same-charge dimuon asymmetry and possible new CP violation sources in the B_s-B_̄s system

Recently, the D0 Collaboration reported a large CP violation in the same-sign dimuon charge asymmetry which has the 3.2σ deviation from the value estimated in the standard model. In this paper, several new physics models are considered: the minimal supersymmetric standard model, the 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 nonanomalous 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 for 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.