Probing next-to-minimal-supersymmetric models with minimal fine tuning by searching for decays of theΥto a lightCP-odd Higgs boson

Abstract

Completely natural electroweak symmetry breaking is easily achieved in supersymmetric models if there is a SM-like Higgs boson, h, with m h < ∼ 100 GeV. In the minimal supersymmetric model, such an h decays mainly to bb and is ruled out by LEP constraints. However, if the MSSM Higgs sector is expanded so that h decays mainly to still lighter Higgs bosons, e.g. h → aa, with Br(h → aa) > 0.7, and if ma < 2m b , then the LEP constraints are satisfied. In this letter, we show that in the next-tominimal supersymmetric model the above h and a properties (for the lightest CP-even and CP-odd Higgs bosons, respectively) imply a lower bound on Br(Υ → γa) that dedicated runs at present (and future) B factories can explore.Low energy supersymmetry remains one of the most attractive solutions to the naturalness / hierarchy problem of the Standard Model (SM). However, the minimal supersymmetric model (MSSM), containing exactly two Higgs doublets, suffers from the "µ problem" and requires rather special parameter choices in order that the light Higgs mass is above LEP limits without electroweak symmetry breaking being "fine-tuned", i.e. highly sensitive to supersymmetry-breaking parameters chosen at the grand-unification scale. Both problems are easily solved by adding Higgs (super) fields to the MSSM. For generic SUSY parameters well-below the TeV scale, finetuning is absent [1] and a SM-like h is predicted with m h < ∼ 100 GeV. Such an h can avoid LEP limits on the tightly constrained e + e − → Z +b ′ s channel if Br(h → bb) is small by virtue of large Br(h → aa), where a is a new light (typically CP-odd) Higgs boson, and m a < 2m b so that a → bb is forbidden [2]. The perfect place to search for such an a is in Upsilon decays, Υ → γa. The simplest MSSM extension, the next-to-minimal supersymmetric model (NMSSM), naturally predicts that the lightest h and a, h 1 and a 1 , have all the right features [1,2,3,4,5]. In this letter, we show that large Br(h 1 → a 1 a 1 ) implies, at fixed m a1 , a lower bound on Br(Υ → γa 1 ) (from now on, Υ is the 1S resonance unless otherwise stated) that is typically within reach of present and future B factories.In the NMSSM, a light a 1 with substantial Br(h 1 → a 1 a 1 ) is a very natural possibility for m Z -scale soft parameters developed by renormalization group running starting from U (1) R symmetric GUT-scale soft parameters [5]. (See also [6,7] for discussions of the light a 1 scenario.) The fine-tuning-preferred m h1 ∼ 100 GeV (for tan β > ∼ f ew) gives perfect consistency with precision electroweak data and the reduced Br(h 1 → bb) ∼ 0.09 − 0.15 explains the ∼ 2.3σ excess at LEP in the Zbb channel at M bb ∼ 100 GeV. The motivation for this scenario is thus very strong.Hadron collider probes of the NMSSM Higgs sector are problematical. The h 1 → a 1 a 1 → 4τ (2m τ < m a1 < 2m b ) or 4 jets (m a1 < 2m τ ) signal is a very difficult one at the Tevatron and very possibly at the LHC [8,9,10,11]. Higgs discovery or, at the very least, certification of a marginal LHC Higgs signal will requi...

Search for Di-Muon Decays of a Light Scalar Higgs Boson in Radiative Upsilon(1S) Decays

“…These results improve the current best limits by a factor of 2-3 for m A 0 < 1.2 GeV/c 2 and are comparable to the previous BABAR result [54] in the mass range of 1.20 < m A 0 < 3.6 GeV/c 2 . Within this range, our limits rule out substantial amount of the parameter space allowed by the light Higgs [41] and axion [43] model. We …”

“…A study of the NMSSM parameter space predicts the branching fraction of Υ(1S ) → γA 0 to be in the range of 10 −6 − 10 −4 depending upon the A 0 mass, tanβ and cosθ A [41].…”

“…The Large hadron collider (LHC) experiment will also not be able to discover such scalar states if h decays primarily into a pair of CP-odd scalars with m 0 A bellow the BB threshold [33,36,37]. In this case, the A 0 can be accessible via the Υ decays [30,31,[38][39][40][41][42] …”

“…Such light state of the A 0 is not excluded by the LEP constraints [32], where the CPeven Higgs boson, h, could decay dominantly into a pair of CP-odd scalars [25,29,[33][34][35][36][37].…”

Search for light CP-odd Higgs decay with a charm tag at BABAR

“…In the next to minimal supersymmetric standard model, for given parameters of the model, the branching ratio of ϒ radiative decays to a CP-odd Higgs boson A 0 is predicted, as a function of the A 0 mass, to lie typically in the range from 10 −7 to 10 −4 [1]. If produced, the A 0 will decay into a fermion pair with a branching fraction proportional to the fermion mass square, so preferentially into the heaviest fermions kinematically allowed.…”