SANCnews: Sector f f bb
In this paper we describe the implementation of processes f(1) (f) over bar (1) ZZ -> 0 and f(1) (f) over bar (1) HZ -> 0 into the framework of SANC system. The f(1) stands for a massless fermion f whose mass is kept non-zero only in arguments of In functions and -> 0 means that all 4-momenta flow inwards. The derived scalar form factors can be used for any cross channel after an appropriate permutation of their arguments (s, t, u). We present the covariant and helicity amplitudes for these processes: for the former only in the annihilation channel f(1) (f) over bar (1) -> ZZ, while for the latter in annihilation f(1) (f) over bar (1) -> HZ and decay H -> Zf(1) (f) over bar (1) channels. We briefly describe additional precomputation modules which were not covered in the previous paper. For the processes f(1) (f) over bar (1) -> HZ(ZZ) and decay H -> Zf(1) (f) over bar (1) we present compact results of calculation of the accompanying bremsstrahlung and discuss exhaustive numerical results. As applications there are two types of the Monte Carlo generators for the process H -> 4 mu. The first one is the generator based on a single resonance approximation for one of the Z bosons. The second one, exploiting the double resonance approximation, is not described in this article. For the generator in the single approximation we present a short description. Whenever possible, we compare our results with those existing in the literature. For example, we present a comparison of the results for H -> 4 mu decay with those obtained by MC generator Prophecy4f.
monte carlo generators feynman diagrams perturbation theory quantum field theory standard model electroweak interactions qcd qed one-loop calculations