Update on a very lightCP-odd scalar in the two-Higgs-doublet model

Abstract

In a previous work we have shown that a general two-Higgs-doublet model (THDM) with a very light CP -odd scalar can be compatible with electroweak precision data, such as the ρ parameter,, and (g − 2) of muon. Prompted by the recent significant change in the theoretical status of the latter observable, we comment on the consequences for this model and update the allowed parameter region. It is found that the presence of a very light scalar with a mass of 0.2 GeV is still compatible with the new theoretical prediction of the muon anomalous magnetic moment.

Scalar sector properties of two-Higgs-doublet models with a global U(1) symmetry

“…1 shows, even m A = 0 is allowed for tan β = 1 and tan β = 5. A light pseudoscalar is experimentally allowed, and various aspects of its phenomenology in the context of 2HDM have been discussed in the literature [41][42][43]. The value tan β = 10 is already large enough so that the conclusion of item 1 applies, and m H drags m A with it.…”

The NMSSM lives: with the 750 GeV diphoton excess

“…This explanation rests on the possibility that a pp → → 2( → γ γ ) process -see Fig. 1 -could not be distinguished from a diphoton signal in the experimental searches [30][31][32][33][34][35][36]. The NMSSM Higgs sector then offers a suitable framework to embed this topology: can be identified with a very light CP-odd singlet decaying dominantly into a diphoton pair, while heavy CP-even doublet and the CP-even singlet have to be combined to mimic a 750 GeV resonance with adequate properties.…”

Supersymmetric one-family model without Higgsinos

“…GeV, which in any case is not troublesome because, as discussed in Ref. [15], a light CP-odd Higgs scalar not only is very difficult to be detected experimentally, but also it has been found that in the two Higgs doublet model type II and when a two-loop calculation is used, a very light (∼ 10 GeV) CP-odd scalar A 0 can still be compatible with precision data such as the ρ parameter, BR(b → sγ), R b , A b , and BR(Υ → A 0 γ) [21]. h e = 0 or very small is a necessary condition in order to have a consistent model, in the sense that it must include a very light neutrino, with masses for the other spin 1/2 neutral particles larger than half the Z 0 mass.…”

“…Immediately following the experimental results a number of papers appeared analyzing the reported value, in terms of various forms of new physics, starting with the simplest extension of the SM to two Higgs doublets [21], or by using supersymmetric extensions, technicolor models, leptoquarks, exotic fermions, extra gauge bosons, extra dimensions, etc., in some cases extending the analysis even at two loops (for a complete bibliography see the various references in [24]). More challenging, although not in complete agreement between the different authors, are the analyses presented in Refs.…”

“…[25] and [26] is outside the scope of the present study, because in our case it depends crucially on the predicted values of the Higgs scalar masses, an obscure matter in supersymmetry. (For example, a exp µ can be understood in the context of our model if the CP-odd scalar has a mass of the order of a few GeV [21], with all the other scalars and supersymmetric particles acquiring masses larger than the electroweak mass scale. Similarly, the light CP-even Higgs boson h with enough suppressed hZZ and hA 0 Z couplings can contribute significantly to a µ [24]).…”