More about the sgoldstino interpretation of HyperCP events

We further discuss possible sgoldstino interpretation of the observation, reported by the HyperCP collaboration, of three Σ⁺ → pμ⁺μ⁻ decay events with the dimuon invariant mass 214.3 MeV within the detector resolution. With a sgoldstino mass equal to 214.3 MeV, this interpretation can be verified at existing and future B and ϕ factories. We find that the most natural values of the branching ratios of two-body B and D meson decays to sgoldstino P and vector meson V are about 10⁻⁶−10⁻⁷. The branching ratios of ϕ meson decay ϕ → Pγ are estimated to be in the range 1.8 × 10⁻¹³−1.6 × 10⁻⁷, depending on the hierarchy of supersymmetry-breaking soft terms. Similar branching ratios for ρ and ω mesons are in the range 10⁻¹⁴−3.4 × 10⁻⁷. The text was submitted by the authors in English.     

Electroweak vacuum stability and diphoton excess at 750 GeV

Recently,both ATLAS and CMS collaborations at the CERN Large Hadron Collider(LHC) announced their observations of an excess of diphoton events around the invariant mass of 750 GeV with a local significance of 3.6σ and 2.6σ,respectively.In this paper,we interpret the diphoton excess as the on-shell production of a real singlet scalar in the pp →S→γγ channel.To accommodate the observed production rate,we further introduce a vector-like fermion F,which carries both color and electric charges.The viable regions of model parameters are explored for this simple extension of the Standard Model(SM).Moreover,we revisit the problem of electroweak vacuum stability in the same scenario,and find that the requirement for the electroweak vacuum stability up to high energy scales imposes serious constraints on the Yukawa coupling of the vector-like fermion and the quartic couplings of the SM Higgs boson and the new singlet scalar.Consequently,a successful explanation for the diphoton excess and the absolute stability of electroweak vacuum cannot be achieved simultaneously in this economical setup.     

Heavy scalar boson in view of the unconfirmed 750 GeV LHC diphoton excess

We discuss the impact of the constraints from the measurements of the parameters of the observed 125 GeV Higgs boson and from the unconfirmed 750 GeV diphoton excess in the LHC experiments on the properties of a possible extra scalar boson predicted in various Standard Model extensions. We consider an SM extension based on a stabilized brane-world model, in which the effective low-energy Lagrangian for the scalar degrees of freedom turns out to be very general and, for different values of the model parameters, reproduces the scalar field Lagrangians of various SM extensions by a singlet scalar. It is shown that in the simplest variant of the model, where only the gravitational degrees of freedom propagate in the bulk, the 125 GeV scalar state can be consistently interpreted as a Higgs-dominated state for a rather wide range of the model parameters, whereas the production cross section of a heavier radion-dominated state with mass 750 GeV or more turns out to be too small in the allowed region of the model parameter space for producing the wouldbe diphoton excess.     

String consistency,heavy exotics,and the 750 GeV diphoton excess at the LHC

String consistency conditions are stronger than anomaly cancellation and can require the addition of exotics in the visible sector. We study such exotics and demonstrate that they may account for the modest excess at 750 GeV in recent diphoton resonance searches performed by the ATLAS and CMS collaborations. In a previous analysis of type II MSSM D‐brane quivers we systematically added up to five exotics for the sake of satisfying string consistency conditions. Using this dataset, we demonstrate that 89780 of the 89964 quivers have exotics, 78155 of which include singlets that may couple to MSSM or exotic multiplets with coupling structures governed by U(1) symmetries that are often anomalous. We demonstrate that certain sets of exotics are far preferred over others and study the structure of singlet couplings to heavy exotics carrying standard model charges. Typical possibilities include singlets that may decay to vector‐like quarks and/or vector‐like leptons and subsequently to two photons. We show that a narrow width diphoton excess can be accounted for while evading existing bounds if multiple exotics are added, with vector‐like leptons of mass GeV and vector‐like quarks with masses up to ≃ 3 TeV. However, a large width , as suggested by the ATLAS data, cannot be easily accommodated in this framework. Renormalization group equations with GUT‐scale boundary conditions show that these supersymmetric models are perturbative and stable. Type IIA compactifications on toroidal orbifolds allow for O(10) Yukawa couplings in the ultraviolet. We also discuss the possibility of accounting for the diphoton excess in a low string scale scenario via the decay of string axions.