Higgs phenomenology in Type-I 2HDM with U(1) H Higgs gauge symmetry

Abstract

It is well known that generic two-Higgs-doublet models (2HDMs) suffer from potentially large Higgs-mediated flavor-changing neutral current (FCNC) problem, unless additional symmetries are imposed on the Higgs fields thereby respecting the Natural Flavor Conservation Criterion (NFC) by Glashow and Weinberg. A common way to respect the NFC is to impose Z 2 symmetry which is softly broken by a dim-2 operator. Another new way is to introduce local U(1) H Higgs flavor symmetry that distinguishes one Higgs doublet from the other. In this paper, we consider the Higgs phenomenology in Type-I 2HDMs with the U(1) H symmetry with the simplest U(1) H assignments that the SM fermions are all neutral under U(1) H , and we make detailed comparison with the ordinary Type-I 2HDM. After imposing various constraints such as vacuum stability and perturbativity as well as the electroweak precision observables and collider search bounds on charged Higgs boson, we find that the allowed Higgs signal strengths in our model are much broader than those in the ordinary Type-I 2HDM, because of newly introduced U(1) H -charged singlet scalar and U(1) H gauge boson. Still the ATLAS data on gg → h → γγ cannot be accommodated. Our model could be distinguished from the ordinary 2HDM with the Z 2 symmetry in a certain parameter region and some channels. If the couplings of the new boson turn out to be close to those in the SM, it would be essential to search for extra U(1) H gauge boson and/or one more neutral scalar boson to distinguish two models.

Higgs and dark matter physics in the type-II two-Higgs-doublet model inspired by E 6 GUT

“…[14][15][16][17]. In the 2HDMs with U(1) H symmetry (denoted as 2HDM U(1) hereafter), two Higgs doublets are charged under new local U(1) H gauge symmetry, and they break both electroweak (EW) and U(1) H Higgs gauge symmetries.…”

“…In fact, the present authors investigated the constraints in the type-I 2HDM U (1) in detail, and discussed the current status of the Type-I 2HDM U (1) in light of the recent LHC results on Higgs properties and provided the future prospects in ref. [14]. Also they constructed the inert 2HDM model with U(1) H gauge symmetry and showed that the light dark matter (DM) mass region below ∼ m W is widely open if the Z 2 symmetry is implemented into local U(1) H gauge symmetry, due to newly open annihilation channels of the DM pair into the extra U(1) H gauge boson(s): HH → Z H Z H , ZZ H , which are not present in the ordinary inert 2HDM with discrete Z 2 symmetry [18].…”

“…In ref. [14], it was shown that the anomaly-free U(1) H charge assignments to the SM fermions are possible in the Type-I 2HDM U (1) , so the fermion sector is just the same as the SM case except right-handed neutrinos. However, in other types of 2HDMs, U(1) H becomes anomalous without extra chiral fermions, and then we face the strong constraints on extra fermions from various experiments.…”

“…In ref. [14], the type-I 2HDM U(1) is mainly discussed and the gauged U(1) H symmetry is anomaly-free without any extra chiral fermions except right-handed neutrinos. In the type-II 2HDM U(1) , the anomaly-free conditions cannot be satisfied without extra fermions [15], so that we have to consider the more complex matter content and U(1) H charge assignment.…”

“…The explicit relations are shown in ref. [14]. The ranges of the parameters are chosen as 1 ≤ tan β ≤ 100, 125 GeV ≤ m A , mh ≤ 1 TeV, 360 GeV ≤ m H + ≤ 1 TeV, |∆m H | ≤ 500 GeV, |α, α 1 , α 2 | ≤ π/2, and 125 GeV ≤ M Z H ≤ 1 TeV.…”