A modular A 4 symmetric scotogenic model for neutrino mass and dark matter

Modular symmetries have been impeccable in neutrino and quark sectors. This motivated us, to propose a variant of scotogenic model based on modular $A_4$ symmetry and realize the neutrino mass generation at one-loop level through radiative mechanism. Alongside, we discuss the lepton flavour violating processes $\mu \to e \gamma$, $\mu \to3e$ and $\mu - e $ conversion in the nucleus. The lightest Dirac fermion turns out to be potential dark matter candidate, made stable by suitable assignment of modular weights. The relic density of the same has been computed with annihilations mediated by inert scalars and new $U(1)$ gauge boson. The LEP-II and ATLAS dilepton constraints on the new gauge parameters are suitably considered to show the consistent parameter region.

One colorful resolution to the neutrino mass generation, three lepton flavor universality anomalies, and the Cabibbo angle anomaly

We propose a simple model to simultaneously explain four observed flavor anomalies while generating the neutrino mass at the one-loop level. Specifically, we address the measured anomalous magnetic dipole moments of the muon, ∆aμ, and electron, ∆ae, the observed anomaly of b → sl+l− in the B-meson decays, and the Cabibbo-angle anomaly. The model consists of four colorful new degrees of freedom: three scalar leptoquarks with the Standard Model quantum numbers (3, 3, −1/3), (3, 2, 1/6), and (3, 1, 2/3), and one pair of down-quark-like vector fermion in (3, 1, −1/3). The baryon number is assumed to be conserved for simplicity.Phenomenologically viable solutions with the minimal number of real parameters can be found to accommodate all the above-mentioned anomalies and produce the approximate, close to 1σ, neutrino oscillation pattern at the same time. From general consideration, the model robustly predicts: (1) neutrino mass is of the normal hierarchy type, and (2) $$ {\mathcal{M}}_{ee}^{\nu } $$ M ee ν ≲ 3 × 10−4 MeV.The possible UV origin to explain the flavor pattern of the found viable parameter space is briefly discussed. The parameter space can be well reproduced within a simple split fermion toy model.

Light, long-lived B − L gauge and Higgs bosons at the DUNE near detector

The low-energy U(1)B−L gauge symmetry is well-motivated as part of beyond Standard Model physics related to neutrino mass generation. We show that a light B − L gauge boson Z′ and the associated U(1)B−L-breaking scalar φ can both be effectively searched for at high-intensity facilities such as the near detector complex of the Deep Underground Neutrino Experiment (DUNE). Without the scalar φ, the Z′ can be probed at DUNE up to mass of 1 GeV, with the corresponding gauge coupling gBL as low as 10−9. In the presence of the scalar φ with gauge coupling to Z′, the DUNE capability of discovering the gauge boson Z′ can be significantly improved, even by one order of magnitude in gBL, due to additional production from the decay φ → Z′Z′. The DUNE sensitivity is largely complementary to other long-lived Z′ searches at beam-dump facilities such as FASER and SHiP, as well as astrophysical and cosmological probes. On the other hand, the prospects of detecting φ itself at DUNE are to some extent weakened in presence of Z′, compared to the case without the gauge interaction.

Extraction of neutrino Yukawa parameters from displaced vertices of sneutrinos

We study displaced signatures of sneutrino pairs potentially emerging at the Large Hadron Collider (LHC) in a Next-to-Minimal Supersymmetric Standard Model supplemented with right-handed neutrinos triggering a Type-I seesaw mechanism. We show how such signatures can be established through a heavy Higgs portal, the sneutrinos then decaying to charged leptons and charginos giving rise to further leptons or hadrons. We finally illustrate how the Yukawa parameters of neutrinos can be extracted by measuring the lifetime of the sneutrino from the displaced vertices, thereby characterising the dynamics of the underlying mechanism of neutrino mass generation. We show our numerical results for the case of both the current and High-Luminosity LHC.

The hubble tension as a hint of leptogenesis and neutrino mass generation

The majoron, a neutrinophilic pseudo-Goldstone boson conventionally arising in the context of neutrino mass models, can damp neutrino free-streaming and inject additional energy density into neutrinos prior to recombination. The combination of these effects for an eV-scale mass majoron has been shown to ameliorate the outstanding $$H_0$$ H 0 tension, however only if one introduces additional dark radiation at the level of $$\Delta N_{\mathrm{eff}} \sim 0.5$$ Δ N eff ∼ 0.5 . We show here that models of low-scale leptogenesis can naturally source this dark radiation by generating a primordial population of majorons from the decays of GeV-scale sterile neutrinos in the early Universe. Using a posterior predictive distribution conditioned on Planck2018+BAO data, we show that the value of $$H_0$$ H 0 observed by the SH$$_0$$ 0 ES collaboration is expected to occur at the level of $$\sim 10\%$$ ∼ 10 % in the primordial majoron cosmology (to be compared with $$\sim 0.1\%$$ ∼ 0.1 % in the case of $$\Lambda $$ Λ CDM). This insight provides an intriguing connection between the neutrino mass mechanism, the baryon asymmetry of the Universe, and the discrepant measurements of $$H_0$$ H 0 .

Low scale leptogenesis in a model with promising CP structure

We consider a simple extension of the standard model, which could give a solution to itsCPissues through both the Peccei–Quinn mechanism and the Nelson–Barr mechanism. Its low energy effective model coincides with the scotogenic model in the leptonic sector. Although leptogenesis is known not to work well at lower reheating temperature than$$10^9$$109 GeV in simple seesaw and scotogenic frameworks, such low reheating temperature could be consistent with both neutrino mass generation and thermal leptogenesis via newly introduced fields without referring to the resonance effect. An alternative dark matter candidate to axion is prepared as an indispensable ingredient of the model.

Displaced vertex signatures of a pseudo-Goldstone sterile neutrino

Low-scale models of neutrino mass generation often feature sterile neutrinos with masses in the GeV-TeV range, which can be produced at colliders through their mixing with the Standard Model neutrinos. We consider an alternative scenario in which the sterile neutrino is produced in the decay of a heavier particle, such that its production cross section does not depend on the active-sterile neutrino mixing angles. The mixing angles can be accessed through the decays of the sterile neutrino, provided that they lead to observable displaced vertices. We present an explicit realization of this scenario in which the sterile neutrino is the supersymmetric partner of a pseudo-Nambu-Goldstone boson, and is produced in the decays of higgsino-like neutralinos and charginos. The model predicts the active-sterile neutrino mixing angles in terms of a small number of parameters. We show that a sterile neutrino with a mass between a few 10 GeV and 200 GeV can lead to observable displaced vertices at the LHC, and outline a strategy for reconstructing experimentally its mixing angles.

A radiatively induced neutrino mass model with hidden local U(1) and LFV processes ℓi → ℓjγ, μ → eZ′ and μe → ee

We investigate a model based on hidden U(1)X gauge symmetry in which neutrino mass is induced at one-loop level by effects of interactions among particles in hidden sector and the Standard Model leptons. Neutrino mass generation is also associated with U(1)X breaking scale which is taken to be low to suppress neutrino mass. Then we formulate neutrino mass matrix, lepton flavor violating processes and muon g − 2 which are induced via interactions among Standard Model leptons and particles in U(1)X hidden sector that can be sizable in our scenario. Carrying our numerical analysis, we show expected ratios for these processes when generated neutrino mass matrix can fit the neutrino data.