Two-body top-quark decay in a circularly polarized laser field

Abstract

Abstract The top quark is distinct from all other fermions due to its high mass and short lifetime. Therefore, it decays rapidly almost exclusively into a light quark and a W + gauge boson. Through all of these properties, the top quark can reveal new details about the standard model and possibly about new physics. In this paper, we have investigated the two-body decay of the top quark ( t → q   W + ), where q represents one of the quarks d, s and b, in the presence of a monochromatic circularly polarized laser field. Using the lowest-order Dirac-Volkov formalism, we have analytically established the expression for the laser-assisted total decay width of the top quark. We have analyzed the dependence of the total decay width, as well as the lifetime and branching ratios (BRs) on the characteristic parameters of the laser. The results indicate that the laser has a decreasing effect on the decay width, leading to an extension of the lifetime. The lifetime behavior inside the laser field is explained by the quantum Zeno effect. More importantly, we find that the laser field with an appropriate frequency and electric field amplitude leads to a modification of the BRs either by the enhancement of the ( t → b   W + ) mode or by the suppression of the ( t → s   W + ) and ( t → d   W + ) modes.