Search

We consider a U (1) B - L model with a Z ′ portal Dirac fermion dark matter (DM) χ of low mass which couples very weakly to the B - L gauge boson Z ′ . An arbitrary B - L charge Q ≠ ± 1 , ± 3 of the DM χ ensures its stability. Motivated by the sensitivity reach of forthcoming "Lifetime Frontier" experiments, we focus on the Z ′ mass, m Z ′ , in the sub-GeV to few GeV range. To evaluate the DM relic abundance, we examine both the freeze-out and freeze-in DM scenarios. For the freeze-out scenario, we show that the observed DM abundance is reproduced near the Z ′ resonance, m χ ≃ m Z ′ / 2 , where m χ is the DM mass. For the freeze-in scenario, we focus on m χ ≪ m Z ′ . We show that for a fixed value of m Z ′ , g BL values roughly scale as 1/Q to reproduce the observed DM abundance. For various Q values in the range between 10 - 6 and 10 2 , we show that the gauge coupling values g BL needed to reproduce the observed DM abundance lie in the search reach of future planned and/or proposed experiments such as FASER, Belle-II, LDMX, and SHiP. In the freeze-in case, the Q values to realize observable g BL values are found to be much smaller than that in the freeze-out case. [ABSTRACT FROM AUTHOR]

We propose a simple non-supersymmetric grand unified theory (GUT) based on the gauge group S O (10) × U (1) ψ . The model includes 3 generations of fermions in 16 ( + 1 ), 10 ( - 2 ) and 1 ( + 4 ) representations. The 16 -plets contain Standard Model (SM) fermions plus right-handed neutrinos, and the 10 -plet and the singlet fermions are introduced to make the model anomaly-free. Gauge coupling unification at M GUT ≃ 5 × 10 15 - 10 16 GeV is achieved by including an intermediate Pati–Salam breaking at M I ≃ 10 12 - 10 11 GeV, which is a natural scale for the seesaw mechanism. For M I ≃ 10 12 - 10 11 , proton decay will be tested by the Hyper-Kamiokande experiment. The extra fermions acquire their masses from U (1) ψ symmetry breaking, and a U (1) ψ Higgs field drives a successful inflection-point inflation with a low Hubble parameter during inflation, H inf ≪ M I . Hence, cosmologically dangerous monopoles produced from SO(10) and PS breakings are diluted away. This is the first SO(10) model we are aware of in which relatively light intermediate mass ( ∼ 10 10 - 10 12 GeV) primordial monopoles can be adequately suppressed. The reheating temperature after inflation can be high enough for successful leptogenesis. With the Higgs field contents of our model, a Z 2 symmetry remains unbroken after GUT symmetry breaking, and the lightest mass eigenstate among linear combinations of the 10 -plet and the singlet fermions serves as a Higgs-portal dark matter (DM). We identify the parameter regions to reproduce the observed DM relic density while satisfying the current constraint from the direct DM detection experiments. The present allowed region will be fully covered by the future direct detection experiments such as LUX-ZEPLIN DM experiment. In the presence of the extra fermions, the SM Higgs potential is stabilized up to M I . [ABSTRACT FROM AUTHOR]

Abstract We propose a novel reformulation of supersymmetric (more precisely μ -) hybrid inflation based on a local U(1) or any suitable extension of the minimal supersymmetric standard model (MSSM) which also resolves the μ problem. We employ a suitable Kahler potential which effectively yields quartic inflation with non-minimal coupling to gravity. Imposing the gravitino Big Bang Nucleosynthesis (BBN) constraint on the reheat temperature (T r ≲ 10 6 GeV) and requiring a neutralino LSP, the tensor to scalar ratio (r) has a lower bound r ≳ 0.004. The U(1) symmetry breaking scale lies between 108 and 1012 GeV. We also discuss a scenario with gravitino dark matter whose mass is a few GeV. [ABSTRACT FROM AUTHOR]

We consider μ -term hybrid inflation which, in its minimal format with gravity mediated supersymmetry breaking, leads to split supersymmetry. The MSSM μ -term in this framework is larger than the gravitino mass m G , and successful inflation requires m G (and hence also | μ | ) ≳ 5 × 10 7 GeV, such that the gravitino decays before the LSP neutralino freezes out. Assuming universal scalar masses of the same order as m G , this leads to split supersymmetry. The LSP wino with mass ≃ 2 TeV is a plausible dark matter candidate, the gluino may be accessible at the LHC, and the MSSM parameter tan ⁡ β ≃ 1.7 in order to be compatible with the measured Higgs boson mass. The tensor-to-scalar ratio r , a canonical measure of gravity waves, can be as high as 0.001. [ABSTRACT FROM AUTHOR]

We explore the dark matter and LHC implications of t − b − τ quasi Yukawa unification in the framework of supersymmetric models based on the gauge symmetry G = SU ( 4 ) c × SU ( 2 ) L × SU ( 2 ) R . The deviation from exact Yukawa unification is quantified by a dimensionless parameter C ( | C | ≲ 0.2 ), such that the Yukawa couplings at M GUT are related by y t : y b : y τ = | 1 + C | : | 1 − C | : | 1 + 3 C | . In contrast to earlier studies which focused on universal gaugino masses, we consider non-universal gaugino masses at M GUT that are compatible with the gauge symmetry G . Our results reveal a variety of neutralino dark matter scenarios consistent with the observations. These include stau and chargino coannihilation scenarios, the A -resonance scenario, as well as Higgsino dark matter solutions which are more readily probed by direct detection searches. The gluino mass is found to be ≲ 4 TeV , the stop mass is ≳ 2 TeV , while the first two family squarks and sleptons are of order 4–5 TeV and 3 TeV respectively. [ABSTRACT FROM AUTHOR]

We present an inflationary model in which the Standard Model Higgs doublet field with non-minimal coupling to gravity drives inflation, and the effective Higgs potential is stabilized by new physics which includes a dark matter particle and right-handed neutrinos for the seesaw mechanism. All of the new particles are fermions, so that the Higgs doublet is the unique inflaton candidate. With central values for the masses of the top quark and the Higgs boson, the renormalization group improved Higgs potential is employed to yield the scalar spectral index n s ≃ 0.968 , the tensor-to-scalar ratio r ≃ 0.003 , and the running of the spectral index α = d n s / d ln ⁡ k ≃ − 5.2 × 10 − 4 for the number of e-folds N 0 = 60 ( n s ≃ 0.962 , r ≃ 0.004 , and α ≃ − 7.5 × 10 − 4 for N 0 = 50 ). The fairly low value of r ≃ 0.003 predicted in this class of models means that the ongoing space and land based experiments are not expected to observe gravity waves generated during inflation. [ABSTRACT FROM AUTHOR]

We explore t-b-τ Yukawa unification (YU) in a supersymmetric SU(4)c× SU(2)L× SU(2)R model without imposing a discrete left-right (L-R) symmetry. A number of interesting solutions that are compatible with t-b-τ YU, LSP neutralino dark matter (DM), and LHC and other experimental constraints are identified. In particular, they include gluino-neutralino and stau-neutralino coannihilation scenarios, where the NLSP gluino mass can range from 1–3 TeV. Higgsino-like dark matter solutions are also identified for which gluino masses can approach 5 TeV or so. This scenario will be tested at LHC Run-3 and its future upgrades. [ABSTRACT FROM AUTHOR]

We explore the gravitational wave spectrum generated by string-wall structures in an S O (10) (S p i n (10)) based scenario of pseudo-Goldstone boson dark matter (pGDM) particle. This dark matter candidate is a linear combination of the Standard Model (SM) singlets present in the 126 and 16 dimensional Higgs fields. The Higgs 126-plet vacuum expectation value (VEV) 〈 126 H 〉 leaves unbroken the Z 2 subgroup of Z 4 , the center of S O (10). Among other things, this yields topologically stable cosmic strings with a string tension μ ∼ 〈 126 H 〉 2. The subsequent (spontaneous) breaking of Z 2 at a significantly lower scale by the 16-plet VEV 〈 16 H 〉 leads to the appearance of domain walls bounded by the strings produced earlier. We display the gravitational wave spectrum for Gμ values varying between 10 − 15 and 10 − 9 (〈 126 H 〉 ∼ 10 11 - 1014 GeV), and 〈 16 H 〉 ∼ 0.1 - 102 TeV range (G denotes Newton's constant.) These predictions can be tested, as we show, by a variety of (proposed) experiments including LISA, ET, CE and others. [ABSTRACT FROM AUTHOR]

The DArk Matter Particle Explorer (DAMPE) has reported a measurement of the flux of high energy cosmic ray electrons plus positrons (CREs) in the energy range between 25 GeV and 4.6 TeV . With unprecedented high energy resolution, the DAMPE data exhibit an excess of the CREs flux at an energy of around 1.4 TeV . In this letter, we discuss how the observed excess can be understood in a minimal framework where the Standard Model (SM) is supplemented by a stable SM singlet scalar as dark matter (DM) and type II seesaw for generating the neutrino mass matrix. In our framework, a pair of DM particles annihilates into a pair of the SM SU(2) triplet scalars (Δs) in type II seesaw, and the subsequent Δ decays create the primary source of the excessive CREs around 1.4 TeV . The lepton flavor structure of the primary source of CREs has a direct relation with the neutrino oscillation data. We find that the DM interpretation of the DAMPE excess determines the pattern of neutrino mass spectrum to be the inverted hierarchy type, taking into account the constraints from the Fermi-LAT observations of dwarf spheroidal galaxies. [ABSTRACT FROM AUTHOR]

Motivated by the recently proposed Trans-Planckian Censorship Conjecture (TCC), we propose a gauged B − L model of inflection-point inflation with axion dark matter. The Hubble scale during inflation (H inf) satisfies the TCC bound of H inf ≲ 1 GeV, the axion dark matter scenario is free from the axion domain wall and isocurvature problems. The seesaw mechanism is automatically incorporated in the model and the observed baryon asymmetry of the universe can be reproduced via resonant leptogenesis. [ABSTRACT FROM AUTHOR]

We consider a U(1) X gauge symmetry extension of the Standard Model (SM) with a Z ′ -portal Majorana fermion dark matter that allows for a relatively light gauge boson Z ′ with mass of 10 MeV− a few GeV and a much heavier dark matter through the freeze-in mechanism. In a second scenario the roles are reversed, and the dark matter mass, in the keV range or so, lies well below the Z ′ mass, say, ∼1 GeV. We outline the parameter space that can be explored for these two scenarios at the future Lifetime Frontier experiments including Belle-II, FASER, LDMX and SHiP. [ABSTRACT FROM AUTHOR]

Motivated by the recently reported measurement of the W boson mass M W = 80.4335 ± 0.0094 GeV by the CDF collaboration, we propose a type III seesaw extension of the minimal supersymmetric standard model (MSSM) which also includes an R-parity violating term. Without taking potential SUSY radiative corrections into account, we show that the CDF measurement of M W and the LEP measurement of the ρ parameter can be simultaneously accommodated at the 2 σ level. A long-lived gravitino in a few GeV mass range is a unique viable dark matter candidate in this framework. [ABSTRACT FROM AUTHOR]

A gauged U (1) X symmetry appended to the Standard Model (SM) is particularly well motivated since it can account for the light neutrino masses by the seesaw mechanism, explain the origin of baryon asymmetry of the universe via leptogenesis, and help implement successful cosmological inflation with the U (1) X breaking Higgs field as the inflaton. In this framework, we propose a light dark matter (DM) scenario in which the U (1) X gauge boson Z ′ behaves as a DM particle in the universe. We discuss how this scenario with Z ′ mass of a few keV and a U (1) X gauge coupling g X ≃ 10 − 16 can nicely fit the excess in the electronic recoil energy spectrum recently reported by the XENON1T collaboration. In order to reproduce the observed DM relic density in the presence of such a tiny gauge coupling, we propose an extension of the model to a two-component DM scenario. The Z ′ DM density can be comparable to the observed DM density by the freeze-in mechanism through the coupling of Z ′ boson to a partner Higgs-portal scalar DM with a large U (1) X charge. [ABSTRACT FROM AUTHOR]