Search

We consider a class of SUSY models in which the MSSM gauge group is supplemented with a gauged U(1)B−L symmetry and a global U(1)R symmetry. This extension introduces only electrically neutral states, and the new SUSY partners effectively double the number of states in the neutralino sector that now includes a blino (from B − L) and singlino from a gauge singlet superfield. If the DM density is saturated by a LSP neutralino, the model yields quite a rich phenomenology depending on the DM composition. The LSP relic density constraint provides a lower bound on the stop and gluino masses of about 3 TeV and 4 TeV respectively, which is testable in the near future collider experiments such as HL-LHC. The chargino mass lies between 0.24 TeV and about 2.0 TeV, which can be tested based on the allowed decay channels. We also find m τ ˜ 1 ≳ 500 GeV, and m e ˜ , m μ ˜ , m v ˜ S , P ≳ 1 TeV. We identify chargino-neutralino coannihilation processes in the mass region 0.24 TeV ≲ m χ ˜ 1 0 ≈ m χ ˜ 1 ± ≲ 1.5 TeV, and also coannihilation processes involving stau, selectron, smuon and sneutrinos for masses around 1 TeV. In addition, A2 resonance solutions are found around 1 TeV, and H2 and H3 resonance solutions are also shown around 0.5 TeV and 1 TeV. Some of the A2 resonance solutions with tan β ≳ 20 may be tested by the A/H → τ+τ− LHC searches.. While the relic density constraint excludes the bino-like DM, it is still possible to realize higgsino, singlino and blino-like DM for various mass scales. We show that all these solutions will be tested in future direct detection experiments such as LUX-Zeplin and Xenon-nT. [ABSTRACT FROM AUTHOR]

We study the implications for bounds on the top quark pole mass m in models with low scale supersymmetry following the discovery of the Standard Model-like Higgs boson. In the minimal supersymmetric standard model, we find that m ≥ 164 GeV, if the light CP even Higgs boson mass m = 125 ± 2 GeV. We also explore the top quark and Higgs boson masses in two classes of supersymmetric SO(10) models with t-b- τ Yukawa coupling unification at M. In particular, assuming SO(10) compatible non-universal gaugino masses, setting m = 125 GeV and requiring 5% or better Yukawa unification, we obtain the result 172 GeV ≤ m ≤ 175 GeV. Conversely, demanding 5% or better t- b- τ Yukawa unification and setting m = 173 .2 GeV, the Higgs boson mass is predicted to lie in the range 122 GeV ≤ m ≤ 126 GeV. [ABSTRACT FROM AUTHOR]

We consider an SO(10) grand unified theory in which the ratio of the SU(2) W and SU(3) c gaugino masses satisfy M2/M3 ≈ 3, which results in the realization of natural supersymmetry. In the MSSM parameter space this relation looks artificial, but in the SO(10) case it results from a field with a designated vacuum expectation value. We consider two models, namely M1: M2: M3 = −1 /5: 3 : 1 ( Case I), and M1 : M2 : M3 = −5 : 3 : 1 ( Case II). Focusing on ameliorating the little hierarchy problem, we explore the parameter space of these models which yield small fine-tuning measuring parameters (natural supersymmetry) at the electroweak scale (Δ EW) as well as at the high scale (Δ HS). Although both models allow for the solution of the little hierarchy problem, the predicted sparticle spectra can differ markedly in the two cases. Depending on the ratio of the bino mass to the other gaugino masses, Case I leads to stau lepton masses of around a 100 GeV, while in Case II, the stau slepton masses are in the several TeV range. In Case I, the bino-like neutralino can be as light as 90 GeV, while the gluino is heavier than 2 TeV or so. In Case II, due to gluino-bino near degeneracy, the bino cannot be lighter than a TeV or so. Having a light neutralino with sizable bino-higgsino mixture in Case I allows the direct dark matter search experiments to test this class of models. [ABSTRACT FROM AUTHOR]

We identify a class of supersymmetric SU(4) c × SU(2) L × SU(2) R models in which imposing essentially perfect t- b- τ Yukawa coupling unification at MGUT yields a mass close to 122–126 GeV for the lightest CP-even (SM-like) Higgs boson. The squark and gluino masses in these models exceed 3 TeV, but the stau and charginos in some cases can be considerably lighter. We display some benchmark points corresponding to neutralino-stau and bino-wino coannihilations as well as A-resonance. The well-known MSSM parameter tan β is around 46–52. [ABSTRACT FROM AUTHOR]

We employ a variety of symmetry breaking patterns in SO(10) and E6 Grand Unified Theories to demonstrate the appearance of topological defects including magnetic monopoles, strings, and necklaces. We show that independent of the symmetry breaking pattern, a topologically stable superheavy monopole carrying a single unit of Dirac charge as well as color magnetic charge is always present. Lighter intermediate mass topologically stable monopoles carrying two or three quanta of Dirac charge can appear in SO(10) and E6 models respectively. These lighter monopoles as well as topologically stable intermediate scale strings can survive an inflationary epoch. We also show the ap- pearance of a novel necklace configuration in SO(10) broken to the Standard Model via SU(4)c × SU(2)L × SU(2)R. It consists of SU(4)c and SU(2)R monopoles connected by flux tubes. Necklaces consisting of monopoles and antimonopoles joined together by flux tubes are also identified. Even in the absence of topologically stable strings, a monopole-string system can temporarily appear. This system decays by emitting gravity waves and we provide an example in which the spectrum of these waves is strongly peaked around 10−4 Hz with Ωqwh2 ≃10−12. This spectrum should be within the detection capability of LISA. [ABSTRACT FROM AUTHOR]

We employ a variety of symmetry breaking patterns in SO(10) and E6 Grand Unified Theories to demonstrate the appearance of topological defects including magnetic monopoles, strings, and necklaces. We show that independent of the symmetry breaking pattern, a topologically stable superheavy monopole carrying a single unit of Dirac charge as well as color magnetic charge is always present. Lighter intermediate mass topologically stable monopoles carrying two or three quanta of Dirac charge can appear in SO(10) and E6 models respectively. These lighter monopoles as well as topologically stable intermediate scale strings can survive an inflationary epoch. We also show the ap- pearance of a novel necklace configuration in SO(10) broken to the Standard Model via SU(4)c × SU(2)L × SU(2)R. It consists of SU(4)c and SU(2)R monopoles connected by flux tubes. Necklaces consisting of monopoles and antimonopoles joined together by flux tubes are also identified. Even in the absence of topologically stable strings, a monopole-string system can temporarily appear. This system decays by emitting gravity waves and we provide an example in which the spectrum of these waves is strongly peaked around 10−4 Hz with Ωqwh2 ≃10−12. This spectrum should be within the detection capability of LISA. [ABSTRACT FROM AUTHOR]

We show how hybrid inflation can be successfully realized in a supersymmetric model with gauge group GPS = SU(4)c × SU(2)L × SU(2)R. By including a non-renormalizable superpotential term, we generate an inflationary valley along which GPS is broken to the standard model gauge group. Thus, catastrophic production of the doubly charged magnetic monopoles, which are predicted by the model, cannot occur at the end of inflation. The results of the cosmic background explorer can be reproduced with natural values (of order 10−3) of the relevant coupling constant, and symmetry breaking scale of GPS of the order of 1016 GeV. The spectral index of density perturbations lies between unity and 0.9. Moreover, the μ-term is generated via a Peccei-Quinn symmetry and proton is practically stable. Baryogenesis in the universe takes place via leptogenesis. The low deuterium abundance constraint on the baryon asymmetry, the gravitino limit on the reheat temperature and the requirement of almost maximal νμ−ντ mixing from SUPER-KAMIOKANDE can be simultaneously met with mνμ, mντ and heaviest Dirac neutrino mass determined from the large angle MSW resolution of the solar neutrino problem, the SUPER-KAMIOKANDE results and SU(4)c symmetry respectively. [ABSTRACT FROM AUTHOR]