Lee-Quigg-Thacker bounds for Higgs boson masses in a two-doublet model

Abstract

Upper bounds for neutral as well as charged Higgs boson masses in a two-doublet model are obtained on the basis of tree unitarity conditionsà la Lee, Quigg and Thacker. A wide variety of scattering processes are considered so extensively that our bounds are more restrictive than those obtained previously for neutral Higgs bosons and are also of a new kind for charged Higgs boson. It is argued that at least one of the Higgs bosons should be lighter than 580 GeV/c 2 . 1 IntroductionAlthough the success of the standard SU (2) W ×U (1) Y gauge theory of the electroweak interactions is overwhelming, the Higgs boson sector in charge of spontaneous symmetry breaking has so far eluded experimental verification and is still a mystery. We all agree that the Higgs boson is one of our central concerns of the present experimental search and will be so even more in the future colliders, JLC, SSC and LHC.It has been known by now rather well that the mass of the Higgs boson, which is proportional to the Higgs quartic coupling, may be bounded from above, provided that the quartic coupling is not so large as to violate the validity of perturbative calculations [1,2]. In fact in the minimal standard model with a single Higgs doublet, Lee, Quigg and Thacker (LQT) [1] deduced the constraint from the perturbative unitarity which turned out to be m h < (8π Casalbuoni et al. [6] have raised a question which has close bearings on LQT's, namely, at what energy strong interaction phenomena would start to show up whenever one or more Higgs masses are sufficiently large. They examined models with two doublets, a doublet plus a singlet and also a supersymmetric model where there exist three Higgs supermultiplets.Maalampi et al. [7] have recently studied the two-doublet model in the same vein as LQT. They derived an upper bound of the neutral Higgs boson mass by a numerical analysis, which gave them more or less the same bound as of LQT. It should be pointed out herewith that they did not consider a broad class of scattering processes to derive constraints on all of the charged and neutral Higgs boson masses.The purpose of the present paper is to reexamine the two-doublet model to see whether one can derive an upper bounds for neutral as well as charged Higgs boson masses in the method of LQT. We will answer to this question in the affirmative by taking into our considerations sufficiently large number of scattering processes. Overall allowed regions of three neutral and one charged Higgs boson masses are explored and their maximally possible values are presented (see Eqs. (45)- (48)). Moreover we will argue that at least one of the Higgs bosons ought to be lighter considerably than might have been expected from the LQT' work (see Eqs. (49) and (50)).

h → Zγ in the complex two Higgs doublet model

“…below solution [31], conforming to perturbative unitarity [32][33][34], and the oblique radiative parameters S, T, U [35,36]. After implementing this algorithm, we have a collection of possible C2HDM data points.…”

CP violating Two-Higgs-Doublet Model: constraints and LHC predictions

“…In refs. [37,38] [39,40]. As for the constraints from experimental data, we take into account EDMs and the S, T and U parameters [41][42][43][44].…”

Large pseudoscalar Yukawa couplings in the complex 2HDM

“…All points comply to the following theoretical constraints: the potential is bounded from below [49], perturbative unitarity is enforced [50][51][52] and all allowed points conform to the oblique radiative parameters [53][54][55].…”