Higgs pair signal enhanced in the 2HDM with two degenerate 125 GeV Higgs bosons

Abstract

We discuss a scenario of the type-II two-Higgs-doublet model (2HDM) in which the [Formula: see text] rate of the Higgs pair production is enhanced due to the two nearly degenerate 125 GeV Higgs bosons (h, H). Considering various theoretical and experimental constraints, we figure out the allowed ranges of the trilinear couplings of these two Higgs bosons and calculate the signal rate of [Formula: see text] from the productions of Higgs pairs (hh, hH, HH) at the large hadron collider (LHC). We find that in the allowed parameter space some trilinear Higgs couplings can be larger than the Standard Model (SM) value by an order and the production rate of [Formula: see text] can be greatly enhanced. We also consider a “decoupling” benchmark point where the light CP-even Higgs has a SM-like cubic self-coupling while other trilinear couplings are very small. With a detailed simulation on the [Formula: see text] signal and backgrounds, we find that in such a “decoupling” scenario the hh and hH channels can jointly enhance the statistical significance to 5[Formula: see text] at 14 TeV LHC with an integrated luminosity of 3000 fb[Formula: see text].