Abstract
Abstract It is pointed out that mixing effects in the CP-even scalar sector of the NMSSM can give 6-8 GeV correction to the SM-like Higgs mass in moderate or large tan β regions with a small value of the singlet-higgs-higgs superfields coupling λ ~ $ \mathcal{O} $ (0.1). This effect comes mainly from the mixing of the SM-like Higgs with lighter singlet. In the same parameter range, the mixing of the heavy doublet Higgs with the singlet may strongly modify the couplings of the singlet-like and the 125 GeV scalars. Firstly, the LEP bounds on a light singlet can be evaded for a large range of its masses. Secondly, the decay rates of both scalars can show a variety of interesting patterns, depending on the lightest scalar mass. In particular, a striking signature of this mechanism can be a light scalar with strongly suppressed (enhanced) branching ratios to $ b\overline{b}\left( {gg,c\overline{c},\gamma \gamma } \right) $ as compared to the SM Higgs with the same mass. The γγ decay channel is particularly promising for the search of such a scalar at the LHC. The 125 GeV scalar can, thus, be accommodated with substantially smaller than in the MSSM radiative corrections from the stop loops (and consequently, with lighter stops) also for moderate or large tan β, with the mixing effects replacing the standard NMSSM mechanism of increasing the tree level Higgs mass in the low tan β and large λ regime, and with clear experimental signatures of such a mechanism.
Highlights
In the pre-discovery era, NMSSM was discussed mainly as a scenario allowing for a Higgs mass significantly above the values predicted by the MSSM [21,22,23,24,25]
The attention has been mostly focused on the new tree-level contribution to the Higgs mass coming from the singlet-doublet-doublet coupling in the superpotential, λSHuHd, which can be significant for low tan β values and O(1) values of λ
In NMSSM, there are three physical neutral CP-even Higgs fields, Hu, Hd, S which are the real parts of the excitations around the real vevs, vu ≡ v sin β, vd ≡ v cos β, vs with v2 = vu2 + vd2 ≈ (174 GeV)2, of the neutral components of doublets Hu, Hd and the singlet S
Summary
We recall the necessary for us facts about the CP-even scalar sector of NMSSM [33]. This scenario is the most natural at moderate and large tan β.5 It is clear from figure 1 that similar correction O(5) GeV to the Higgs mass can be obtained from the s − hmixing for a larger range of the singlet-dominated scalar mass ms, provided one can evade the LEP bounds given by the red curve in the left panel of figure 1 by suppressing the sbb and sτ τcouplings. This is because in such a case, s decays predominantly into charm quarks and gluons and b-tagging cannot be used to enhance the signal over background ratio so the most stringent constraints on g2s come from the flavour independent Higgs searches in hadronic final states at LEP [40]. Be obtained for a broad range 60 GeV < ms < 110 GeV, and secondly the decay rates of s and h can have interesting patterns
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