The field content of the NMSSM is very similar to the MSSM; it differs merely by the addition of a singlet superfield S, which is introduced to address the μ-problem of the MSSM (for an exhaustive review of the NMSSM see e.g. [1]). The superpotential and soft supersymmetry-breaking terms of the Higgs sector are given by

The phenomenology of this model can be easily connected to the simplified models that we have reviewed previously. If we disregard the Higgsinos and singlino (which if heavy are largely irrelevant for Higgs phenomenology) the Higgs sector of the NMSSM is essentially that of a Type II `2HDM + Scalar' model, where we can immediately identify H_d, H_u as H₁,H₂.

The singlet scalar S = [1/(√2)](S_R + i S_I) can obtain a vacuum expectation value 〈S 〉 = v_s, generating an effective μ parameter μ_eff = λv_s. The presence of additional light singlet scalars, pseudoscalars, and fermions allows for exotic Higgs decays within the NMSSM. On this page we discuss decays to light CP-even scalars s or pseudoscalars a of the form

(3)

Decays to fermions are covered here. There are three ways of realizing the above decays within the NMSSM. In each case, the exotic Higgs decay phenomenology is a subset of the Type II 2HDM+S discussed in §, with some additional restrictions (like −π/2 < α < 0). The first is an accidental cancellation resulting in a light singlet-like s or a. Recent examples of such models have been found in a parameter scan [2]. By choosing λ, κ ∼ 0.5, |A_λ| <~150  GeV and A_κ  ∼ 0 the lightest pseudoscalar can satisfy m_a < m_h/2 for a SM-like Higgs h, with Br(h → a a) or Br(h → Z a)  ∼ O(0.1). On the other hand, λ, κ ∼ 0.5, A_λ  ∼ 0−200  GeV and A_κ  ∼ − 500  GeV can result in a singlet-like light Higgs satisfying m_s < m_h/2 with Br(h → s s)  ∼ O(0.1). There are also two symmetry limits resulting in light pseudoscalars, namely the R-limit and the PQ-limit of the NMSSM. The R-symmetry limit is realized for A_λ , A_κ → 0 [3,4,5], defined by the scalar field transformations

(4)

This global symmetry is spontaneously broken by the Higgs vacuum expectation values v_u, v_d, v_s, which results in a massless Nambu-Goldstone boson (the R-axion) appearing in the spectrum:

(5)

where

In most of the parameter space v_s = [(μ_eff)/(λ)] >> vsin2 β, making A_R mostly singlet-like. To avoid cosmological constraints on a massless axion and to help stabilize the vacuum, the R-symmetry is usually taken to be approximate. This leads to a light, mostly singlet-like pseudo-goldstone boson, and depending on the exact parameters chosen opens up the possibility of h→ aa for a = A_R. Through its A component, a then decays to SM fermions, dominantly b―b and τ⁺ τ⁻ above the respective thresholds. For κ, A_κ → 0  [6,7,8,9,10,11,12,13,14,15], there is an approximate PQ-symmetry:

(6)

The PQ-symmetry limit is also shared by some other singlet-extensions of the MSSM, including the nearly-MSSM (nMSSM) [16] and the general NMSSM (e.g., see [1]). Analogously to the R-limit there is a PQ-axion,

 (7)

Exotic Higgs decays to this pseudoscalar, and even the singlet-like scalar, are in principle possible. However, for m_h = 125  GeV, exotic Higgs decays to (pseudo-)scalars are generically not dominant in the PQ-limit. Instead, decays to binos and singlinos can dominate. This is discussed here.

References

[2]N. D. Christensen, T. Han, Z. Liu, and S. Su, Low-Mass Higgs Bosons in the NMSSM and Their LHC Implications, [arXiv:1303.2113]. [3]B. A. Dobrescu and K. T. Matchev, Light Axion Within the Next-to-Minimal Supersymmetric Standard Model, JHEP 0009 (2000) 031, [hep-ph/0008192]. [4]R. Dermisek and J. F. Gunion, The NMSSM Close to the R-symmetry Limit and Naturalness in h → aa Decays for m_a < 2m_b, Phys.Rev. D75 (2007) 075019, [hep-ph/0611142]. [5]D. E. Morrissey and A. Pierce, Modified Higgs Boson Phenomenology from Gauge or Gaugino Mediation in the NMSSM, Phys.Rev. D78 (2008) 075029, [arXiv:0807.2259]. [6]R. Peccei and H. R. Quinn, Constraints Imposed by CP Conservation in the Presence of Instantons, Phys.Rev. D16 (1977) 1791-1797. [7]R. Peccei and H. R. Quinn, CP Conservation in the Presence of Instantons, Phys.Rev.Lett. 38 (1977) 1440-1443. [8]E. Chun, Natural mu term with Peccei-Quinn symmetry, Phys.Lett. B348 (1995) 111-114, [hep-ph/9411290]. [9]P. Ciafaloni and A. Pomarol, Dynamical determination of the supersymmetric Higgs mass, Phys.Lett. B404 (1997) 83-88, [hep-ph/9702410]. [10]L. J. Hall and T. Watari, Electroweak supersymmetry with an approximate U(1)(PQ), Phys.Rev. D70 (2004) 115001, [hep-ph/0405109]. [11]B. Feldstein, L. J. Hall, and T. Watari, Simultaneous solutions of the strong CP and mu problems, Phys.Lett. B607 (2005) 155-164, [hep-ph/0411013]. [12]D. Miller and R. Nevzorov, The Peccei-Quinn axion in the next-to-minimal supersymmetric standard model, [hep-ph/0309143]. [13]R. Barbieri, L. J. Hall, A. Y. Papaioannou, D. Pappadopulo, and V. S. Rychkov, An Alternative NMSSM phenomenology with manifest perturbative unification, JHEP 0803 (2008) 005, [arXiv:0712.2903]. [14]O. Lebedev and S. Ramos-Sanchez, The NMSSM and String Theory, Phys.Lett. B684 (2010) 48-51, [arXiv:0912.0477]. [15]B. A. Dobrescu, G. L. Landsberg, and K. T. Matchev, Higgs boson decays to CP odd scalars at the Tevatron and beyond, Phys.Rev. D63 (2001) 075003, [ hep-ph/0005308]. [16]C. Panagiotakopoulos and K. Tamvakis, New minimal extension of MSSM, Phys. Lett. B 469 (1999) 145, [hep-ph/9908351].

---

File translated from T_EX by T_TH, version 4.03. On 15 Dec 2013, 22:46.