Z0-Boson Decays in a Strong Electromagnetic Field

The probability of Z(0)-boson decay to a pair of charged fermions in a strong electromagnetic field, Z(0) -> (f) over barf, is calculated. On the basis of a method that employs exact solutions to relativistic wave equations for charged particles, an analytic expression for the partial decay width Gamma(x) = Gamma (Z(0) -> (f) over barf) is obtained at an arbitrary value of the parameter = eM(z)(-3) root-(F(mu nu)q(nu))(2), which characterizes the external-field strength. The total Z(0)-boson decay width in an intense electromagnetic field, Gamma(Z)(x), is calculated by summing these results over all known generations of charged leptons and quarks. It is found that, in the region of relatively weak fields (x < 0.06), the field-induced corrections to the standard Z(0)-boson decay width in a vacuum do not exceed 2%. As x increases, the total decay width Gamma(Z)(x) develops oscillations against the background of its gradual decrease to the absolute-minimum point. At x(min) = 0.445, the total Z(0)-boson decay width reaches the minimum value of Gamma(Z)(x(min)) = 2.164 GeV, which is smaller than the Z(0)-boson decay width in a vacuum by more than 10%. In the region of superstrong fields (x > 1), Gamma(Z)(x) grows monotonically with increasing external-field strength. In the region x > 5, the t-quark-production process Z(0) -> (t) over bart, which is forbidden in the absence of an external field, begins contributing significantly to the total decay width of the Z(0) boson.