We reveal a set of novel decay topologies for the 125 GeV Higgs boson in supersymmetry which are initiated by its decay into a pair of neutralinos, and discuss their collider search strategies. This category of exotic Higgs decays is characterized by the collider signature: visible objects þ E T , with E T dominantly arising from escaping dark matter particles. Their benchmark arises naturally in the Peccei-Quinn symmetry limit of the minimal supersymmetric standard model singlet extensions, which is typified by the coexistence of three light particles: singletlike scalar h 1 and pseudoscalar a 1 , and singlinolike neutralino χ 1 , all with masses of ≲10 GeV, and the generic suppression of the exotic decays of the 125 GeV Higgs boson h 2 → h 1 h 1 , a 1 a 1 and χ 1 χ 1 , however. As an illustration, we study the decay topology: h 2 → χ 1 χ 2 , where the binolike χ 2 decays to h 1 χ 1 or a 1 χ 1 , and h 1 =a 1 → ff, with ff ¼ μ þ μ − , bb. In the dimuon case (m h 1 =a 1 ∼ 1 GeV), a statistical sensitivity of S= ffiffiffi ffi B p > 6σ can be achieved easily at the 8 TeV LHC, assuming σðpp → Wh 2 Þ=σðpp → Wh SM ÞBrðh 2 → μ þ μ − χ 1 χ 1 Þ ¼ 0.1. In the bb case (m h 1 =a 1 ∼ 45 GeV), 600 fb −1 data at the 14 TeV LHC can lead to a statistical sensitivity of S= ffiffiffi ffi B p > 5σ, assuming σðpp → Zh 2 Þ=σðpp → Zh SM ÞBrðh 2 → bbχ 1 χ 1 Þ ¼ 0.5. (SUSY). The Higgs mass stabilization mechanism generally manifests itself through Higgs couplings absent in the standard model (SM). The 125 GeV Higgs boson therefore is expected to be a leading window into NP.Because the 125 GeV SM Higgs decay width is small (Γ ∼ 4 MeV), a new coupling between the Higgs boson and some light particles may lead to a large exotic Higgs decay branching fraction. The current bounds on such channels are still weak: a branching fraction as large as ∼60% is allowed at the 2σ C.L. [3][4][5][6][7], in a general context, e.g., if new physics is allowed to enter the Higgs-glue-glue coupling. If SM couplings are assumed, theorist-performed fits constrain the invisible branching fraction to be ≲25% at 95% C.L. [3,4]. Even with the full 300 fb −1 of the 14 TeV LHC, the projected upper bound is ∼10% at the 2σ C.L. on such channels [8] (mainly driven by estimates of systematic errors), which still leaves appreciable room for an exotic decay mode. Searches for exotic decays are therefore very natural and effective tools to explore possible and exciting new couplings to the 125 GeV Higgs boson.Exotic Higgs decays are often grouped into two categories according to their collider signatures: (1) purely E T and (2) visible objects (no E T , except for neutrinos from heavy quark or tau decays). Case (1) is mainly dark matter (DM) motivated and was originally studied in [9]. A well-known example for case (2) is the R-symmetry limit of the next-tominimal supersymmetric standard model (NMSSM) [10], in which the SM-like Higgs can significantly decay to a pair of light singletlike R axions (a 1 ).Separately, there is the deep cosmic mystery of DM. In the past decade...

The ATLAS and CMS collaborations have announced discovery of a ∼ 125 GeV Higgs boson, after a combined analysis of the di-photon and ZZ search channels. This observation has significant impact on low-energy supersymmetry. First, some fine-tuning is necessary to accommodate such a Higgs mass in the Minimal Supersymmetric Standard Model (MSSM) because the tree-level mass of the SM-like Higgs boson in the MSSM is relatively small. We study the possibility of lifting the mass of the SM-like Higgs boson by non-decoupling D-term from an additional U (1) gauge symmetry. In particular, we focus on a gauged Peccei-Quinn symmetry which can also be related to a possible solution of the µ problem in the MSSM. In addition to the measurement of the mass of the Higgs, the data also reveals a tantalizing hint of a significantly enhanced di-photon signal rate, 1.56 ± 0.43 and 1.9 ± 0.5 times of the SM prediction in the CMS and ATLAS experiments, respectively. We demonstrate that such an enhancement can be accommodated in this MSSM extension. Anomaly cancellation requires the introduction of charged exotics. If some of them happen to be light and have sizable coupling to the SM-like Higgs boson, the di-photon signal rate can be enhanced significantly. EW precision measurements provide stringent constraints on this model. Taking these into account, we identify two benchmark scenarios. We argue that they are representative of large classes of viable models beyond our current example which can consistently enhance the Higgs to di-photon rate. We also comment on possible signals of such light exotics at the LHC.

Many new physics models predict sizable modifications to the SM Zbb couplings, while the corresponding measurements at LEP and SLC exhibit some discrepancy with the SM predictions. After updating the current results on the Zbb coupling constraints from global fits, we list the observables that are most important for improving the Zbb coupling constraints and estimate the expected precision reach of three proposed future e + e − colliders, CEPC, ILC and FCC-ee. We consider both the case that the results are SM-like and the one that the Zbb couplings deviate significantly from the SM predictions. We show that, if we assume the value of the Zbb couplings to be within 68% CL of the current measurements, any one of the three colliders will be able to rule out the SM with more than 99.9999% CL (5σ). We study the implications of the improved Zbb coupling constraints on new physics models, and point out their complementarity with the constraints from the direct search of new physics particles at the LHC, as well as with Higgs precision measurements. Our results provide a further motivation for the construction of future e + e − colliders.

We continue our exploration of the nearly Peccei-Quinn symmetric limit shared by common singlet extensions of the Minimal Supersymmetric Standard Model. This limit has been established as a viable framework for studying sub-electroweak scale dark matter phenomenology and has interesting and direct connections to new exotic Higgs decay physics. We present analytic calculations to motivate the important phenomenological features mentioned above. We also discuss benchmark points in this model framework that accommodate the observed Galactic Center gamma ray excess. We emphasize connections between phenomenology of dark matter direct detection and indirect detection, and new exotic decay channels for the 125 GeV Higgs boson. We conclude by identifying two benchmark modes of exotic Higgs decays for h → τ + τ − E T and h → bb E T final states and estimate their sensitivity prospects at the LHC.