Nondecoupling of charged scalars in Higgs decay to two photons and symmetries of the scalar potential

TL;DR

This paper investigates how the nondecoupling behavior of charged scalars in multi-Higgs models affects Higgs to diphoton decay measurements, showing that symmetries in the scalar potential can enable decoupling even for heavy scalars.

Contribution

It demonstrates that specific global symmetries in the scalar potential can restore decoupling of charged scalars, constraining multi-Higgs models through Higgs decay data.

Findings

Charged scalars exhibit nondecoupling in certain models.

Global continuous symmetries can enable decoupling of heavy scalars.

Higgs to diphoton measurements impose strong constraints on multi-Higgs models.

Abstract

A large class of two- and three-Higgs-doublet models with discrete symmetries has been employed in the literature to address various aspects of flavor physics. We analyse how the precision measurement of the Higgs to diphoton signal strength would severely constrain these scenarios due to the nondecoupling behavior of the charged scalars, to the extent that the number of additional scalar doublets can be constrained no matter how heavy the nonstandard scalars are. We demonstrate that if the scalar potential is endowed with appropriate global continuous symmetries together with soft breaking parameters, decoupling can be achieved thanks to the unitarity constraints on the mass-square differences of the heavy scalars.