CMS results for the $\gamma \gamma$ production at the LHC: do they give a hint for a Higgs boson of the maximally CP symmetric two-Higgs-doublet model?

Abstract

Recent measurements of the CMS experiment at the LHC show possibly, with about 3 $\sigma$ significance, a resonance in di-photon events with an invariant mass of 95.4 GeV. If this resonance can be confirmed, this could be a hint for a new elementary particle beyond the Standard Model. An additional Standard-model-like Higgs boson with this mass could be excluded by the CMS experiment. We investigate whether this resonance could fit into a two-Higgs-doublet model highly constrained by CP symmetry, the so-called maximally-CP-symmetric model (MCPM). In the strict symmetry limit of the MCPM only the fermions of the third generation obtain masses. We discuss a mechanism where the first and second generation fermions get masses through effects from interactions with very high mass particles. The latter can be integrated out at LHC energies giving effective Lagrangian terms, among them these mass terms. This procedure also gives us a Cabibbo-Kobayashi-Maskawa (CKM) matrix which automatically satisfies some salient structural features observed in experiments. We call the resulting theory MCPM'. Our finding shows that indeed the enhancement measured by CMS could originate from the pseudoscalar Higgs boson $h''$ of this model. According to the model the boson $h''$ would mainly be produced in the Drell-Yan reaction by charm-anticharm-quark fusion. The main decay mode of $h''$ is predicted to be $h'' \to c\bar{c}$. We then consider the so called oblique parameters $S$, $T$, $U$ which give us an allowed region for the mass of the scalar Higgs boson $h'$ versus that of the charged ones $H^\pm$ of the MCPM'. We calculate the effect of these charged bosons $H^\pm$ in the leptonic decays of the charm mesons $D^\pm$ and the charm-strange mesons $D_s^\pm$. Our results indicate that the mass $m_{H^\pm}$ of the charged Higgs bosons $H^\pm$ of the MCPM' should be around 300 GeV.