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]

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]