SANCnews: Sector ffbb

TL;DR

This paper advances the SANC framework by implementing one-loop electroweak corrections for the ffZZ and ffHZ sectors, including both annihilation and decay channels, with a comprehensive CA/FF/HA formalism and new precomputation blocks. It details renormalization procedures, bremsstrahlung treatment, and numerical results that compare SANC outputs against established tools (e.g., Denner, Grace-Loop, Prophecy4f, CompHEP), highlighting both successful agreements and areas needing refinement. The work also introduces a Monte Carlo generator for H → 4μ in single and double resonance schemes, and provides a practical user guide for deploying the FF/HA/BR modules, making the framework ready for collider phenomenology where precise one-loop corrections are essential for Higgs background studies. The combination of building-block precomputation, cross-channel flexibility, and MC integration significantly enhances the precision toolkit for Higgs and electroweak processes at colliders.

Abstract

In this paper we describe the implementation of processes f_1 bar-f_1 ZZ --> 0 and f_1 bar-f_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 ln 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 bar-f_1 --> ZZ, while for the latter in annihilation f_1 bar-f_1 --> HZ and decay H --> Z f_1 bar-f_1 channels. We briefly describe additional precomputation modules which were not covered in the previous paper. For the processes f_1 bar-f_1 --> HZ(ZZ) and decay H --> Z f_1 bar-f_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 --> 4μ. 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 μdecay with those obtained by MC generator Prophecy4f.

Figures (12)

• Figure 1: Born $ffHZ(ZZ)\to 0$ diagrams, $t$ and $u$ channels.
• Figure 2: Born $ffHZ\to 0$ diagrams, $s$ channel.
• Figure 3: $H\to f_1\bar{f}_1 Z$ decay kinematics.
• Figure 4: "Right" $bbb$ vertex in $ffbb$ processes.
• Figure 5: "Left" $bff$ vertex in $ffbb$ processes.