New regions in the NMSSM with a 125 GeV Higgs

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 ∼ 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 bb (gg, cc, γγ) 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.

Enhanced Higgs associated production with a top quark pair in the NMSSM with light singlets

“…Notice also that in the limitM 2 hH = 0, tth is enhanced forM 2 hsM 2 Hs > 0 (< 0) if the singlet-like scalar is lighter (heavier) than 125 GeV. This is because in this limit mixing of the Higgs with lighter (heavier) singlet-like scalar pushes up (down) the Higgs mass so m 2 h −M 2 hh is positive (negative) [35][36][37]. It is also interesting to note that in principle large cot (β − α) may be also obtained for very heavy non-SM Higgs doublet if |M 2 Hs | is large enough.…”

“…in ref. [37], is not relevant for our discussion, since in the general NMSSM there is enough freedom in the parameter space to set them to arbitrary values.…”

Blind spots for neutralino dark matter in the NMSSM

“…This region is particularly interesting because the Higgs-singlet mixing can increase the Higgs boson mass by up to about 6 GeV [24]. While this enhancement of the Higgs mass by mixing effects can be present both for small and large tan β, it is worth emphasizing that for large (or moderate) values of tan β this is a unique way to have lighter stops than in the MSSM.…”

“…While this enhancement of the Higgs mass by mixing effects can be present both for small and large tan β, it is worth emphasizing that for large (or moderate) values of tan β this is a unique way to have lighter stops than in the MSSM. Moreover, for large tan β the singlet-dominated scalar coupling to bottom quarks can be strongly suppressed relaxing the LEP constraints on scalars and allowing a substantial correction to the Higgs mass from mixing for a wide range of singlet masses between about 60 and 110 GeV [24] (for small tan β a sizable correction from mixing is allowed only for the singlet mass in the vicinity of the LEP excess at 98 GeV [25,26]). …”

“…In the presence of non-negligible mixing between the singlet and the Higgs doublet f (N ) s is generically large if m s < m h . Light singlet-dominated scalar with sizable mixing with the Higgs scalar is particularly well motivated since it can enhance the Higgs scalar mass even by 6 GeV as compared to the MSSM, allowing for relatively light stops in NMSSM, even for large tan β [24].…”