Quantum interference effects in Higgs boson pair-production beyond the Standard Model

TL;DR

This paper investigates how quantum interference between nearly degenerate Higgs bosons in extended models affects the pair-production cross section of the 125 GeV Higgs at the LHC, highlighting the importance of including these effects in phenomenological analyses.

Contribution

It demonstrates the significant impact of interference effects between nearly degenerate Higgs states on Higgs pair-production predictions in extended models beyond the Standard Model.

Findings

Interference can substantially change the predicted cross section.

Including interference effects is crucial for accurate phenomenology.

Results impact current bounds and future searches at the LHC.

Abstract

New physics frameworks like the Next-to-Minimal Supersymmetric Standard Model and the Next-to-2-Higgs-doublet Model contain three neutral CP-even Higgs bosons. It is possible for the heavier two of these states to have masses identical to each other, which can result in a sizeable quantum interference between their propagators in processes they mediate. For both these models, we study the impact of such interference on the pair-production of the lightest of the three scalars, which we identify with the observed 125 GeV Higgs boson, in the gluon-fusion channel at the Large Hadron Collider (LHC). We find that the inclusion of these effects can substantially alter the cross section, compared to its value when they are ignored, for this process. Our results illustrate the importance of taking possible quantum interference effects into account not only when investigating the phenomenology of extended Higgs sectors at the future Run(s) of the LHC, but also when imposing its current exclusion bounds on the parameter spaces of these models.