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In this paper, we perform a detail analysis on the phenomenology of Z portal scalar and Dirac fermion dark matter in B − L scotogenic Dirac model. Unconventional B − L charge Q is assigned to the right-handed neutrino ν R in order to realise scotogenic Dirac neutrino mass at one-loop level, where three typical value Q = − 1 4 , − 4, 3 2 are chosen to illustrate. Observational properties involving dilepton signature at LHC, relativistic degrees of freedom N eff , dark matter relic density, direct and indirect detections are comprehensively studied. Combined results of these observables for the benchmark scenarios imply that the resonance region M DM ∼ M Z /2 is the viable parameter space. Focusing on the resonance region, a scanning for TeV-scale dark matter is also performed to obtain current allowed and future prospective parameter space.

In this paper we propose a radiated linear seesaw model where the naturally small term µ L are generated at one-loop level and its soft-breaking of lepton number symmetry attributes to the spontaneous breaking(SSB) of B-L gauge symmetry. The value of B − L charges for new particles are assigned to satisfy the anomalies cancelation. It is founded that some new particles may have exotic values of B − L charge such that there exists residual Z 2 × Z ′ 2 symmetry even after SSB of B − L gauge symmetry. The Z 2 × Z ′ 2 discrete symmetry stabilizes the these particles as dark matter candidates. In the model, two classes of inert fermions and scalars with different B − L charges are introduced, leading to two-component dark matter candidates. The lepton flavor violation processes, the relic density of dark matter, the direct detection of dark matter and the phenomenology at LHC are investigated. * wjnwang96@aliyun.com †

In this paper, we thoroughly investigate the LHC phenomenology of the type II seesaw mechanism for neutrino masses in the nondegenerate case where the triplet scalars of various charge (H ±± , H ± , H 0 , A 0 ) have different masses. Compared with the degenerate case, the cascade decays of scalars lead to many new, interesting signal channels. In the positive scenario where M H ±± < M H ± < M H 0 /A 0 , the four-lepton signal is still the most promising discovery channel for the doubly-charged scalars H ±± . The five-lepton signal is crucial to probe the mass spectrum of the scalars, for which, for example, a 5σ reach at 14 TeV LHC for M H ± = 430 GeV with M H ±± = 400 GeV requires an integrated luminosity of 76 fb −1 . And the six-lepton signal can be used to probe the neutral scalars H 0 /A 0 , which are usually hard to detect in the degenerate case. In the negative scenario where M H ±± > M H ± > M H 0 /A 0 , the detection of H ±± is more challenging, when the cascade decay H ±± → H ± W ± * is dominant. The most important channel is the associated H ± H 0 /A 0 production in the final state ± E T b bb b, which requires a luminosity of 109 fb −1 for a 5σ discovery, while the final state ± E T b bτ + τ − is less promising. Moreover, the associated H 0 A 0 production can give same signals as the standard model Higgs pair production. With a much larger cross section, the H 0 A 0 production in the final state b bτ + τ − could reach 3σ significance at 14 TeV LHC with a luminosity of 300 fb −1 . In summary, with an integrated luminosity ∼ O(500 fb −1 ), the triplet scalars can be fully reconstructed at 14 TeV LHC in the negative scenario.

If neutrinos are Dirac fermions, certain new physics beyond the standard model should exist to account for the smallness of neutrino mass. With two additional scalars and a heavy intermediate fermion, in this paper, we systematically study the general mechanism that can naturally generate the tiny Dirac neutrino mass at tree and in one-loop level. For tree level models, we focus on natural ones, in which the additional scalars develop small vacuum expectation values without fine-tuning. For one-loop level models, we explore those having dark matter candidates under Z D 2 symmetry. In both cases, we concentrate on SU(2) L multiplet scalars no larger than quintuplet, and derive the complete sets of viable models. Phenomenologies, such as lepton flavor violation, leptogenesis, DM and LHC signatures are briefly discussed.