Eur. Phys. J. C (2018) 78: 649
https://doi.org/10.1140/epjc/s10052-018-6127-z

Special Article - Tools for Experiment and Theory

Unitarity constraints on general scalar couplings with SARAH

¹ Laboratoire de Physique Théorique et Hautes Energies (LPTHE), UMR 7589, Sorbonne Université et CNRS, 4 place Jussieu, 75252, Paris Cedex 05, France
² Institute for Theoretical Physics (ITP), Karlsruhe Institute of Technology, Engesserstraße 7, 76128, Karlsruhe, Germany
³ Institute for Nuclear Physics (IKP), Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen, Germany

^* e-mail: florian.staub@kit.edu

Received: 4 June 2018
Accepted: 1 August 2018
Published online: 14 August 2018

Abstract

We present an update of the Mathematica package SARAH to calculate unitarity constraints in BSM models. The new functions can perform an analytical and numerical calculation of the two-particle scattering matrix of (uncoloured) scalars. We do not make use of the simplifying assumption of a very large scattering energy, but include all contributions which could become important at small energies above the weak scale. This allows us to constrain trilinear scalar couplings. However, it can also modify (weakening or strengthening) the constraints on quartic couplings, which we show via the example of a singlet extended Standard Model.