In supersymmetric theories like the Next-to-Minimal Supersymmetric Standard Model (NMSSM), the lightest neutralino with bino or singlino as its dominant component is customarily taken as dark matter (DM) candidate. Since light Higgsinos favored by naturalness can strength the couplings of the DM and thus enhance the DM-nucleon scattering rate, the tension between naturalness and DM direct detection results becomes more and more acute with the improved experimental sensitivity. In this work, we extend the NMSSM by inverse seesaw mechanism to generate neutrino mass, and show that in certain parameter space the lightest sneutrino may act as a viable DM candidate, i.e. it can annihilate by multi-channels to get correct relic density and meanwhile satisfy all experimental constraints. The most striking feature of the extension is that the DM-nucleon scattering rate can be naturally below its current experimental bounds regardless of the higgsino mass, and hence it alleviates the tension between naturalness and DM experiments. Other interesting features include that the Higgs phenomenology becomes much richer than that of the original NMSSM due to the relaxed constraints from DM physics and also due to the presence of extra neutrinos, and that the signatures of sparticles at colliders are quite different from those with neutralino as DM candidate.
Natural Next-to-Minimal Supersymmetric Standard Model (nNMSSM) is featured by predicting one CP-even Higgs boson satisfying m h 1 120 GeV and Higgsinos lighter than about 300 GeV, and consequently the cross section for DM-nucleon scattering in this scenario is usually quite large. We study the diphoton signal of the light Higgs boson in nNMSSM by considering the tight constraints from the latest LUX and PandaX-II experiments, and we conclude that the optimal value of the signal rate at 8 TeV LHC is greatly reduced in comparison with earlier predictions. For example, previous studies indicated that the rate may exceed 120 fb for m h 1 80 GeV, while it is at most 25 fb if the lightest neutralino in the scenario is fully responsible for the measured DM relic density. We also investigate the case of m h 1 98 GeV which is hinted by the excesses of the LEP analysis on Zbb signal and the CMS analysis on the diphoton signal. We conclude that nNMSSM can explain simultaneously the excesses at 1σ level without violating any known constraints.
Recently, the Dark Matter Particle Explorer (DAMPE) experiment released the new measurement of the total cosmic e þ e − flux between 25 GeV and 4.6 TeV, which indicates a spectral softening at around 0.9 TeV and a tentative peak at around 1.4 TeV. We utilize a scalar dark matter (DM) model to explain the DAMPE peak by χχ → Z 0 Z 0 → lll 0 l 0 with an additional anomaly-free gauged Uð1Þ family symmetry, in which χ, Z 0 , and l ð0Þ denote, respectively, the scalar DM, the new gauge boson, and l ð0Þ ¼ e, μ, τ with m χ ∼ m Z 0 ∼ 2 × 1.5 ðTeVÞ. We first illustrate that the minimal framework G SM × Uð1Þ Y 0 with the above mass choices can explain the DAMPE excess, which, however, be excluded by LHC constraints from the Z 0 searches. Then, we study a nonminimal framework G SM × Uð1Þ Y 0 × Uð1Þ Y 00 in which Uð1Þ Y 00 mixes with Uð1Þ Y 0 . We show that such a framework can interpret the DAMPE data and at the same time survive all other constraints including the DM relic abundance, DM direct detection, and collider bounds. We also investigate the predicted e þ e − spectrum in this framework and find that the mass splitting Δm ¼ m χ − m Z 00 should be less than about 17 GeV to produce the peaklike structure.
Inspired by the peak structure observed by recent DAMPE experiment in e + e − cosmic-ray spectrum, we consider a scalar dark matter (DM) model with gauged U (1) L e −L μ symmetry, which is the most economical anomaly-free theory to potentially explain the peak by DM annihilation in nearby subhalo. We utilize the process χχ → Z Z → lll l , where χ , Z , l ( ) denote the scalar DM, the new gauge boson and l ( ) = e, μ, respectively, to generate the e + e − spectrum. By fitting the predicted spectrum to the experimental data, we obtain the favored DM mass range m χ 3060
+80−100 GeV and m ≡ m χ − m Z 14 GeV at 68% Confidence Level (C.L.). Furthermore, we determine the parameter space of the model which can explain the peak and meanwhile satisfy the constraints from DM relic abundance, DM direct detection and the collider bounds. We conclude that the model we consider can account for the peak, although there exists a tension with the constraints from the LEP-II bound on m Z arising from the cross section measurement of e + e − → Z * → e + e − .
To explain the small neutrino masses, heavy Majorana neutrinos are introduced in the leftright twin Higgs model. The heavy neutrinos, together with the charged scalars and the heavy gauge bosons, may contribute large mixings between the neutrinos and the charged leptons, which may induce some distinct lepton flavor violating processes. We will check thel i ℓ j (i, j = e, µ, τ, i = j) productions in the γγ collision in the left-right twin Higgs model, and find that the production rates may be large in some specific parameter space, in the optimal cases even possible to be detected with reasonable kinematical cuts. we have also shown that these collisions can constrain effectively the model parameters such as the Higgs vacuum expectation value and the right-handed neutrino mass, etc., and may serve as a sensitive probe of this new physics model.
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