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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.

We study the gauged U (1) Lµ−Lτ scotogenic model with emphasis on latest measurement of LHCb R K ( * ) anomaly and AMS-02 positron excess. In this model, neutrino masses are induced at one-loop level with Z 2 -odd particles, i.e., right-handed neutrinos N ( = e, µ, τ ) and inert scalar doublet η inside the loop. Meanwhile, the gauged U (1) Lµ−Lτ symmetry is broken spontaneously by the scalar singlet S, resulting to the massive gauge boson Z . Provided certain couplings to quarks induced by heavy vector-like quarks, the gauge boson Z would contribute to the transition b → sµ + µ − , hence explain the R K ( * ) anomaly. As for the Majorana fermion DM N , the gauge boson Z and the singlet Higgs H 0 will generate various annihilation channels, among which the N N → Z Z and N N → Z H 0 (→ Z Z ) channel could be used to interpret the AMS-02 positron excess. We give a comprehensive analysis on model parameter space with consider various current constraints.The combined analysis shows that the R K ( * ) anomaly and AMS-02 positron excess can be explained simultaneously.obvious antiproton excess is observed [40]. This can be interpreted by DM dominantly annihilating into leptonic final states [41,42]. Therefore, the current direct and indirect detection experiments seem to advocate 'leptophilic DM' [43]. And U (1) Lµ−Lτ DM is clearly a good choice [8].With holding such benefits, we thus consider the phenomenology of the gauged U (1) Lµ−Lτ scotogenic model [11] in this paper, which has been studied in Refs. [11,12] with emphasizing neutrino mass and dark matter properties for light Z . According to Ref. [12], 50 MeV M Z 400 MeV with 3 × 10 −4 g 10 −3 is required to explain (g − 2) µ and DM relic density. Lately, searches for Z in the e + e − → µ + µ − Z , Z → µ + µ − channel by BABAR has rejected M Z > 212 MeV with g 7 × 10 −4[44]. Although not fully excluded at current, the future experiments, such as Belle-II and SPS, are able to exclude the whole low Z mass region favored by (g − 2) µ and DM [45][46][47][48]. Therefore, we move on to the high mass region M Z 10 GeV and specially focus on R K ( * ) anomaly and AMS-02 positron excess, which has not been discussed in previous studies [11,12].This paper is organized as following. In Sec. II, we briefly review the gauged U (1) Lµ−Lτ scotogenic model. Interpretation of the R K ( * ) anomaly is discussed in Sec. III, and relative constraints on Z in the high mass region are summarised in Sec. III A. A detail scanning on the DM parameter space under constraints from relic density and direct detection are performed in Sec. IV. In Sec. V, we provide benchmarks to fit positron excess by using latest AMS-02 measurement and discuss relative constraints imposed by indirect detections. Finally, Sec. VI is devoted to conclusion. II. THE MODEL A. Model SetupThe gauged U (1) Lµ−Lτ scotogenic model was proposed in Ref. [11]. Comparing with the original scotogenic model [2], this model further introduces one additional singlet scalar S charged +1 under U (1) Lµ−Lτ to break this symmetry sp...

We consider the feasibility of interpreting the R K ( * ) anomaly in the colored Zee-Babu model. The model generates neutrino masses at two loops with the help of a scalar leptoquark S ∼ (3, 3, − 1 3 ) and a scalar diquark ω ∼ (6, 1, − 2 3 ), and contributes to the transition b → s − + via the exchange of a leptoquark S at tree level. Under constraints from lepton flavor violating (LFV) and flavor changing neutral current (FCNC) processes, and direct collider searches for heavy particles, we acquire certain parameter space that can accommodate the R K ( * ) anomaly for both normal (NH) and inverted (IH) hierarchies of neutrino masses. We further examine the LFV decays of the B meson, and find a strong correlation with the neutrino mass hierarchy, i.e., Br(for IH. Among these decays, only B + → K + µ ± e ∓ in the case of NH is promising at the LHCb RUN II, while for IH all LFV decays are hard to detect in the near future. *

Lepton number violation plays an essential role in many scenarios of neutrino mass generation and also provides new clues to search new physics beyond the standard model. We consider the neutrinophilic two-Higgs-doublet model (ν-2HDM) where additional right-handed neutral fermions N Ri and a complex singlet scalar σ are also involved. In scalar sector, the global U (1) L symmetry is spontaneous broken, leading to Nambu-Goldstone boson, the Majoron J, accompanied by the Majorana neutrino mass generation. We find that the massless Majoron will induce large invisibleHiggs decay, and current experiments have already set constraints on relevant parameters. For the first time, we point out that the ν-2HDM with N Ri can be distinguished from other seesaw by the same sign tri-lepton signature 3 ± 4j + E T . More interesting, for O(keV) scale Majoron, it is a good candidate of decaying dark matter to interpret the 3.5 keV and 511 keV line excesses by two different parameter spaces. * wjnwang96@aliyun.com †