摘要
The one-loop contributions to the chromomagnetic dipole momentˆμt(q2)and electric dipole momentˆd t(q2)of the top quark are calculated within the reduced 331 model(RM331)for non-zero q2.It is argued that the results are gauge independent and thus represent valid observable quantities.In the RM331,ˆμt(q2)receives new contributions from two heavy gauge bosons,namely Z′and V±,and one neutral scalar boson h2,along with a new contribution from the standard model's Higgs boson via flavor changing neutral currents.The latter,which is also mediated by the Z′gauge boson and the scalar boson h2,can provide a non-vanishingˆd t(q2)if there is a CP-violating phase.The analytical results are presented in terms of both Feynman parameter integrals and Passarino-Veltman scalar functions,which are useful to cross-check the numerical results.Bothˆμt(q2)andˆd t(q2)are numerically evaluated for parameter values still allowed by the constraints from experimental data.It is found that the new one-loop contributions of the RM331 to the real(imaginary)part ofˆμt(q2)are of the order of 10−5(10−6),which means at least three orders of magnitude smaller than the standard model prediction but larger than the predictions of other models of new physics.In the RM331,the dominant contribution arises from the V±gauge boson for‖q‖in the 30-1000 GeV interval and a mass mV of the order of a few hundreds of GeV.As forˆd t(q2),it receives its largest contribution from h2 exchange and can reach values of the order of 10−19,i.e.,smaller than the contributions predicted by other standard model extensions.
