The Anomalous Chromomagnetic Dipole Moment of the Top Quark in Different Frameworks

We give explicit formulae for the anomalous chromomagnetic dipole moment of the top quark in the framework of the standard model, the two higgs doublet model and the minimal supersymmetric standard model. Finally, we compare the results for this coupling with the bound −0.03 ≤ ∆κ ≤ 0.01 coming from analysis of b → sγ process whith an on-shell gluon. The top quark is the heaviest fermion in the standard model (SM) with a mass of 174± 5.2 GeV. Anomalous couplings between top quark and gauge bosons might affect top quark production and its decay at high energies. On the other hand, the t̄tg coupling correction to the total top quark production cross section at Fermilab was calculated by Stange et. al. [1], in the framework of the SM. Since the anomalous chromomagnetic dipole moment of the top quark appears in the top quark cross section, it is possible, due to uncertainties, to estimate the constraints that it would impose on the ∆κ. For the LHC, the anomalous coupling is constrained to lie in the range −0.09 ≤ ∆κ ≤ 0.1 [2]. Also the influence of an anomalous ∆κ on the cross section and associated gluon jet energy for tt̄g has been analized, it leads to a bound of −2.1 ≤ ∆κ ≤ 0.6. Anomalous couplings of the top quark to on-shell gluons would modify the rate for B → Xsγ [3]. Using the recent data from CLEO collaboration for the branching fraction of the process B(b → sγ) [4], we update the previous analysis done in reference [3] and get the new allowed region for the anomalous chromomagnetic dipole moment of the top quark to be −0.03 ≤ ∆κ ≤ 0.01.