Tiny Neutrino Masses Research Articles

Phenomenology of extended multiHiggs doublet models with S4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$S_4$$\\end{document} family symmetry

We propose extended 3HDM and 4HDM models where the SM gauge symmetry is enlarged by the spontaneously broken S4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$S_4$$\\end{document} group, the preserved Z2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Z_2$$\\end{document} and broken Z4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Z_4$$\\end{document} cyclic symmetries. Each model has three active SU(2) scalar doublets, in addition, the first one has an extra inert scalar singlet, whereas the second model has an inert scalar doublet. Furthermore, each model has several extra gauge singlet scalars, which are triplets under S4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$S_4$$\\end{document}. Both models yield the same structure of the mass matrices for the fermion sector, where a radiative seesaw generates the tiny light active neutrino masses at one-loop level, through the S4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$S_4$$\\end{document} triplets. The presence of flavor changing neutral currents mediated by heavy scalars allowed us to study the (K0-K¯0)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(K^0-\\overline{K}^0)$$\\end{document} and (Bd,s0-B¯d,s0)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(B_{d,s}^0-\\overline{B}_{d,s}^0)$$\\end{document} meson mixings, in the parameter space that currently satisfies the experimental constraints. On the other hand, due to the preserved Z2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Z_2$$\\end{document} symmetry, our proposed models have stable scalar and fermionic dark matter candidates. Furthermore, these models are consistent with the current pattern of SM fermion masses and mixings, with the measured dark matter relic abundance and successfully accommodate the constraints arising from meson oscillations and oblique parameters. The extra scalars in our models provide radiative corrections to the oblique parameters, where due to the presence of the scalar inert doublet, renders the 4HDM less restrictive than the 3HDM one.

Probing chiral and flavored Z′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Z^\\prime $$\\end{document} from cosmic bursts through neutrino interactions

The origin of tiny neutrino mass is an unsolved puzzle leading to a variety of phenomenological aspects beyond the Standard Model (BSM). We consider U(1) gauge extension of the Standard Model (SM) where so-called seesaw mechanism is incarnated with the help of thee generations of Majorana type right-handed neutrinos followed by the breaking of U(1) and electroweak gauge symmetries providing anomaly free structure. In this framework, a neutral BSM gauge boson Z′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Z^\\prime $$\\end{document} is evolved. To explore the properties of its interactions we consider chiral (flavored) frameworks where Z′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Z^\\prime $$\\end{document} interactions depend on the handedness (generations) of the fermions. In this paper we focus on Z′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Z^\\prime $$\\end{document}-neutrino interactions which could be probed from cosmic explosions. We consider νν¯→e+e-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ u \\overline{\ u } \\rightarrow e^+ e^-$$\\end{document} process which can energize gamma-ray burst (GRB221009A, so far the highest energy) through energy deposition. Hence estimating these rates we constrain U(1) gauge coupling (gX)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(g_X)$$\\end{document} and Z′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Z^\\prime $$\\end{document} mass (MZ′)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(M_{Z^\\prime })$$\\end{document} under Schwarzchild (Sc) and Hartle-Thorne (HT) scenarios. We also study ν\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ u $$\\end{document}-DM scattering through Z′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Z^\\prime $$\\end{document} to constrain gX-MZ′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$g_X-M_{Z^\\prime }$$\\end{document} plane using IceCube data considering high energy neutrinos from cosmic blazar (TXS0506+056), active galaxy (NGC1068), the Cosmic Microwave Background (CMB) and the Lyman-α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha $$\\end{document} data, respectively. Finally highlighting complementarity we compare our results with current and prospective bounds on gX-MZ′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$g_X-M_{Z^\\prime }$$\\end{document} plane from scattering, beam-dump and g-2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$g-2$$\\end{document} experiments. [PICS code].

Probing large extra dimension at DUNE using beam tunes

The Deep Underground Neutrino Experiment (DUNE) is a leading experiment in neutrino physics which is presently under construction. DUNE aims to measure the yet unknown parameters in the three flavor oscillation case which includes discovery of leptonic CP violation, determination of the neutrino mass hierarchy and measuring the octant of θ23. Additionally, the ancillary goals of DUNE include probing the subdominant effects induced by possible physics beyond the Standard Model (BSM). One such new physics scenario is the possible presence of Large Extra Dimension (LED) which can naturally give rise to tiny neutrino masses. LED impacts neutrino oscillation through two new parameters, — namely the lightest Dirac mass m0 and the radius of the extra dimension RED (< 2 μm). At the DUNE baseline of 1300 km, the probability seems to be modified more at the higher energy (≳ 4 − 5 GeV) in presence of LED. In this work, we attempt to constrain the parameter space of m0 and RED by performing a statistical analysis of neutrino data simulated at DUNE far detector (FD). We illustrate how a combination of the standard low energy (LE) neutrino beam and a medium energy (ME) neutrino beam can take advantage of the relatively large impact of LED at higher energy and improve the constraints. In the analysis we also show the role of the individual oscillation channels (νμ → νe, νμ → νμ, νμ → ντ), as well as the two neutrino mass hierarchies.

Effective Interactions for the SM Fermion Mass Hierarchy and their Possible UV Realization

Abstract We build an extended two Higgs doublet model theory with spontaneously broken $U(1) _{X}$ global symmetry, where the tree-level universal seesaw mechanism generates the mass hierarchy of the Standard Model charged fermions and the Zee–Babu mechanism produces tiny active neutrino masses. The third family of SM charged fermions gets tree-level masses from Yukawa interactions involving the Higgs doublets $H_1$ (for the top quark) and $H_2$ (for the bottom quark and tau lepton). The model under consideration is consistent with SM fermion masses and mixings, with the muon and electron $g-2$ anomalies, and successfully accommodates the constraints arising from charged-lepton-flavor violation and meson oscillations. The proposed model predicts rates for charged-lepton-flavor-violating decays within the reach of forthcoming experiments.

Probing dirac neutrino properties with dilepton signature

The neutrinophilic two Higgs doublet model is one of the simplest models to explain the origin of tiny Dirac neutrino masses. This model introduces a new Higgs doublet with eV scale VEV to naturally generate the tiny neutrino masses. Depending on the same Yukawa coupling, the neutrino oscillation patterns can be probed with the dilepton signature from the decay of charged scalar H±\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$H^\\pm $$\\end{document}. For example, the normal hierarchy predicts BR(H+→e+ν)≪\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(H^+\\rightarrow e^+\ u )\\ll $$\\end{document} BR(H+→μ+ν)≈\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(H^+\\rightarrow \\mu ^+\ u )\\approx $$\\end{document} BR(H+→τ+ν)≃0.5\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(H^+\\rightarrow \ au ^+\ u )\\simeq 0.5$$\\end{document} when the lightest neutrino mass is below 0.01 eV, while the inverted hierarchy predicts BR(H+→e+ν)/2≃\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(H^+\\rightarrow e^+\ u )/2\\simeq $$\\end{document} BR(H+→μ+ν)≃\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(H^+\\rightarrow \\mu ^+\ u )\\simeq $$\\end{document} BR(H+→τ+ν)≃0.25\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(H^+\\rightarrow \ au ^+\ u )\\simeq 0.25$$\\end{document}. By precise measurement of BR(H+→ℓ+ν)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(H^+\\rightarrow \\ell ^+\ u )$$\\end{document}, we are hopefully to probe the lightest neutrino mass and the atmospheric mixing angle θ23\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ heta _{23}$$\\end{document}. Through the detailed simulation of the dilepton signature and corresponding backgrounds, we find that the 3 TeV CLIC could discover MH+≲1220\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$M_{H^+}\\lesssim 1220$$\\end{document} GeV for NH and MH+≲1280\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$M_{H^+}\\lesssim 1280$$\\end{document} GeV for IH. Meanwhile, the future 100 TeV FCC-hh collider could probe MH+≲1810\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$M_{H^+}\\lesssim 1810$$\\end{document} GeV for NH and MH+≲2060\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$M_{H^+}\\lesssim 2060$$\\end{document} GeV for IH.

Phenomenological aspects of the fermion and scalar sectors of a S4 flavored 3-3-1 model

We proposed a viable and predictive model based on the SU(3)C×SU(3)L×U(1)X gauge symmetry, supplemented by the global U(1)Lg symmetry, the S4 family symmetry and several auxiliary cyclic symmetries, which successfully reproduces the experimentally observed SM fermion mass and mixing pattern. The tiny active neutrino masses are generated through an inverse seesaw mechanism mediated by right-handed Majorana neutrinos. The model is consistent with the SM fermion masses and mixings and successfully accommodates the current Higgs diphoton decay rate constraints as well as the constraints arising from oblique S, T and U parameters and we studied the meson mixing due to flavor changing neutral currents mediated by heavy scalars, finding parameter space consistent with experimental constraints.

Heavy neutral leptons in gauged U(1) L µ −L τ at muon collider* *Supported by the National Natural Science Foundation of China (12375074, 11805081) and the Natural Science Foundation of Shandong Province, China (ZR2019QA021)

Heavy neutral leptons N are the most appealing candidates to generate tiny neutrino masses. We studied the signature of heavy neutral leptons in gauged at a muon collider. Charged under the symmetry, the heavy neutral leptons can be pair produced via the new gauge boson at the muon collider as and . We then performed a detailed analysis on the lepton number violation signature and at the 3 TeV muon collider, where the hadronic decays of W boson are treated as fat-jets J. These lepton number violation signatures have quite clean backgrounds at the muon collider. Our simulation shows that a wide range of viable parameter space is within the reach of the 3 TeV muon collider. For instance, with new gauge coupling and an integrated luminosity of 1000 fb , the signal could probe TeV. Meanwhile, if the gauge boson mass satisfies , the signature would be more promising than the signature.

Probing for chiral Z′ gauge boson through scattering measurement experiments

Motivated by the observation that tiny neutrino mass cannot be explained within the framework of the Standard Model, we consider extra gauge extended scenarios in which tiny neutrino masses are generated through the seesaw mechanism. These scenarios are equipped with a beyond the Standard Model neutral gauge boson called Z′ in the general U(1)X symmetry, which is a linear combination of U(1)Y and U(1)B−L. In this case, left- and right-handed fermions interact differently with the Z′. The Z′ gives rise to different processes involving neutrino-nucleon, neutrino-electron, electron-nucleus, and electron-muon scattering processes. By comparing with proton and electron beam-dump experiment data, recast data from searches for the long-lived and dark photon at , LHCb, and CMS experiments, the electron and muon g−2 data, and the data of the dilepton and dijet searches at the LEP experiment, we derive bounds on the gauge coupling and the corresponding gauge boson mass for different U(1)X charges and evaluate the prospective limits from the future beam-dump scenarios at DUNE, FASER (2), and ILC. We conclude that large parameter regions could be probed by scattering, beam-dump, and collider experiments in the future. Published by the American Physical Society 2024

General approach to neutrino mass mechanisms with sterile neutrinos

We present a mathematical framework for constructing the most general neutrino mass matrices that yield the observed spectrum of light active neutrino masses in conjunction with arbitrarily many heavy sterile neutrinos, without the need to assume a hierarchy between Dirac and Majorana mass terms. The seesaw mechanism is a byproduct of the formalism, along with many other possibilities for generating tiny neutrino masses. We comment on phenomenological applications of this approach, in particular deriving a mechanism to address the long-standing (g−2)μ anomaly in the context of the left-right symmetric model. Published by the American Physical Society 2024

Low scale leptogenesis in singlet-triplet scotogenic model

The scotogenic model presents an elegant and succinct framework for elucidating the origin of tiny neutrino masses within the framework of the Standard Model, employing radiative corrections within the domain of the dark sector. We investigate the possibility of achieving low-scale leptogenesis in the singlet-triplet scotogenic model (STSM), where dark matter mediates neutrino mass generation. We initially considered a scenario involving two moderately hierarchical heavy fermions, N and Σ, wherein the lepton asymmetry is generated by the out-of-equilibrium decay of both particles. Our analysis indicates that the scale of leptogenesis in this scenario is similar to that of standard thermal leptogenesis and is approximately M N,Σ ∼ 109 GeV, which is comparable to the Type-I seesaw case. Further, we consider the case with three heavy fermions (N 2, N 2, and Σ) with the hierarchy M N 1 < M Σ ≪ MM N 2 , which yields the lower bound on heavy fermions up to 3.1 TeV, therefore significantly reduce the scale of the leptogenesis up to TeV scale. The only prerequisite is suppression in the N 1 and Σ Yukawa couplings, which causes suppressed washout effects and a small active neutrino mass of about 10-5 eV. This brings about the fascinating insight that experiments aiming to measure the absolute neutrino mass scale can test low-scale leptogenesis in the scotogenic model. Further, the hyperchargeless scalar triplet Ω provides an additional contribution to mass of the W-boson explaining CDF-II result.

Disentangle neutrino electromagnetic properties with atomic radiative pair emission

We elaborate the possibility of using the atomic radiative emission of neutrino pair (RENP) to probe the neutrino electromagnetic properties, including magnetic and electric dipole moments, charge radius, and anapole. With the typical O\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{O} $$\\end{document}(eV) momentum transfer, the atomic RENP is sensitive to not just the tiny neutrino masses but also very light mediators to which the massless photon belongs. The neutrino EM properties introduce extra contribution besides the SM one induced by the heavy W/Z gauge bosons. Since the associated photon spectrum is divided into several sections whose boundaries are determined by the final-state neutrino masses, it is possible to identify the individual neutrino EM form factor elements. Most importantly, scanning the photon spectrum inside the particular section with deviation from the SM prediction once observed allows identification of the neutrino EM form factor type. The RENP provides an ultimate way of disentangling the neutrino EM properties to go beyond the current experimental searches or observations.

A minimal inverse seesaw model with S4 flavour symmetry

We construct an S4 flavour symmetric minimal inverse seesaw model where the standard model is extended by adding two right-handed and two standard model gauge singlet neutrinos to explain the origin of tiny neutrino masses. The resulting model describes the lepton mass spectra and flavour mixing quite well for the case of the normal hierarchy of neutrino masses. The prediction of the model on the Dirac CP-violating phase is centered around 370.087°. Furthermore, using the allowed region for the model parameters, we have calculated the value of the effective Majorana neutrino mass, |〈mee〉|, which characterizes neutrinoless double beta decay.

Interplay among gravitational waves, dark matter and collider signals in the singlet scalar extended type-II seesaw model

We study the prospect of simultaneous explanation of tiny neutrino masses, dark matter (DM), and the observed baryon asymmetry of the Universe in a Z3-symmetric complex singlet scalar extended type-II seesaw model. The complex singlet scalar plays the role of DM. Analyzing the thermal history of the model, we identify the region of the parameter space that can generate a first-order electroweak phase transition (FOEWPT) in the early Universe, and the resulting stochastic gravitational waves (GW) can be detected at future space/ground-based GW experiments. First, we find that light triplet scalars do favor an FOEWPT. In our study, we choose the type-II seesaw part of the parameter space in such a way that light triplet scalars, especially the doubly charged ones, evade the strong bounds from their canonical searches at the Large Hadron Collider (LHC). However, the relevant part of the parameter space, where FOEWPT can happen only due to strong SM doublet-triplet interactions, is in tension with the SM-like Higgs decay to a pair of photons, which has already excluded the bulk of this parameter space. On the other hand, the latest spin-independent DM direct detection constraints from XENON-1T and PANDA-4T eliminate a significant amount of parameter space relevant for the dark sector assisted FOEWPT scenarios, and it is only possible when the complex scalar DM is significantly underabundant. In short, we conclude from our analysis that the absence of new physics at the HL-LHC and/or various DM experiments in the near future will severely limit the prospects of detecting a stochastic GW at future GW experiments and will exclude the possibility of electroweak baryogenesis within this model.

Baryogenesis

The standard model of particle physics describes matter and antimatter as coming from the same fields and this fact has been confirmed experimentally. It is then curious that the observable universe is made of matter and not antimatter. We will first discuss the evidence that we live in a matter-dominated (or matter-antimatter asymmetric) Universe and then proceed to discuss if this can be explained according to our current understanding of the cosmology and particle physics. We will argue that an important process known as baryogenesis to generate a cosmic matter-antimatter asymmetry had to occur before the Universe was a few second old. Then, we will discuss the necessary ingredients for a successful baryogenesis and point out that the current model contains all the ingredients but not in a sufficient amount. Finally, we will discuss possible extensions to the current model which allow successful baryogenesis and how they can be tested experimentally. Interestingly, they might also be connected to other open puzzles in the fundamental physics, like the tiny neutrino mass.

Linear seesaw mechanism from dark sector

We propose a minimal model where a dark sector seeds neutrino mass generation radiatively within the linear seesaw mechanism. Neutrino masses are calculable, since tree-level contributions are forbidden by symmetry. They arise from spontaneous lepton number violation by a small Higgs triplet vacuum expectation value. Lepton flavour violating processes e.g. μ → eγ can be sizeable, despite the tiny neutrino masses. We comment also on dark-matter and collider implications.

On the Higgs spectra of the 3-3-1 model with the sextet of scalars engendering the type II seesaw mechanism

In the 3-3-1 model with right-handed neutrinos (331RHNs), three triplets of scalars engender the correct sequence of symmetry breaking, SU(3)C×SU(3)L×U(1)X→SU(3)C×SU(2)L×U(1)Y→SU(3)C×U(1)EM, generating mass for all fermions, except neutrinos. Tiny neutrino masses may be achieved by implementing the type II seesaw mechanism into the model, requiring the addition of one sextet of scalars to the original scalar content. As consequence, it emerges a very complex scalar sector, involving terms that violate lepton number explicitly, too. The main obstacle to the development of the phenomenology of such scenario is the knowledge of its spectrum of scalars since, now, there are 15 massive scalar particles on it. The proposal of this work is to do an exhaustive analysis of such scalar sector with lepton number being explicitly violated at low, electroweak and high energy scales by means of trilinear terms in the potential. The first case can be addressed analytically and, as a nice result, we have observed that the scalar content of such case is split into two categories: One belonging to the 331 energy scale and the other belonging to the EWSB energy scale, with the last recovering the well know 2THDM + triplet. For the other cases, the scalar sector can be addressed only numerically. Hence, we proposed a very general approach for the numerical study of the potential, avoiding simplifications that can make us reach conclusions without foundation. We show that, in the case of lepton number being explicitly violated at electroweak scale, it is possible to recover the same physics of the 2HDM + triplet, as the previous case. Among all the possibilities, we call the attention to one special case which generates the 3HDM+triplet scenario. For the last case, when lepton number is violated at high energy scale, the sextet becomes very massive and decouples from the original scalar content of the 3-3-1 model. We also discuss, when possible, the phenomenological aspects of each case.

Can we really detect relic neutrinos?

Detecting relic neutrinos is a longstanding goal in fundamental physics. Experimentally, this goal is extremely challenging as the required energy resolution is defined by the tiny neutrino masses (\sim∼ 10 meV). The current consensus is that sufficient statistics together with a clean spectrum could only be achieved if beta decayers are attached to a solid state substrate. However, this inevitably imposes irreducible intrinsic limitations on the energy resolution coming from Heisenberg’s uncertainty principle. This limitation appears to be critical for the currently accepted decayer - Tritium. Here, we analyze the state of the art approaches to mitigate this limitation and conclude that the most promising solution is to change Tritium for a heavier emitter. We find that the two suitable candidates are ^{171}171Tm, ^{63}63Ni.

Charged Higgs induced 5 and 6 lepton signatures from heavy neutrinos at the LHC

We propose an anomaly free gauged U(1) extension of the SM where three right handed heavy neutrinos, being charged under the general U(1) gauge group, are introduced to explain the origin of the tiny neutrino mass through the seesaw mechanism after the general U(1) symmetry is broken. Due to the breaking of the general U(1) symmetry a neutral beyond the standard model gauge boson Z^prime acquires mass. There are two Higgs doublets in this model where one interacts with the SM fermions and the other one interacts with the right handed heavy neutrinos and charged leptons. The charged multiplet of the second Higgs can completely decay into the heavy neutrinos and charged lepton in the neutrinophilic limit of the model parameters. The charged Higgs pair production can be influenced due to presence of the Z^prime boson at the High Luminosity LHC (HL-LHC) in addition to the neutral SM gauge bosons. The pair produced charged Higgs bosons decay into SM charged leptons and heavy neutrinos. Following the leading decay modes of the heavy neutrinos into charged leptons and W boson we study the 5 and 6 lepton final states after the leptonic and hadronic decay of the W bosons considering solely muons and electrons in the final state. Combining the electron and muon final states we estimate the significance of the 5 and 6 charged lepton processes in the m_{H^pm }-m_N plane for different benchmark points of m_{Z^prime }. It is found that the 5 (6) charged lepton processes could be probed at the High Luminosity LHC (HL-LHC) with at least 5 (3) sigma significance and there are parameter regions where the significance could be larger.

Sterile neutrino portal dark matter in nu THDM

In this paper, we propose the sterile neutrino portal dark matter in nu THDM. This model can naturally generate tiny neutrino mass with the neutrinophilic scalar doublet Phi _{nu } and sterile neutrinos N around TeV scale. Charged under a Z_2 symmetry, one Dirac fermion singlet chi and one scalar singlet phi are further introduced in the dark sector. The sterile neutrinos N are the mediators between the DM and SM. Depending on the coupling strength, the DM can be either WIMP or FIMP. For the WIMP scenario, pair annihilation of DM into NN is the key channel to satisfy various bounds, which could be tested at indirect detection experiments. For the FIMP scenario, besides the direct production of DM from freeze-in mechanism, contributions from late decay of NLOP is also important. When sterile neutrinos are heavier than the dark sector, NLOP is long-lived due to tiny mixing angle between sterile and light neutrinos. Constrains from free-streaming length, CMB, BBN and neutrino experiments are considered.

Leptogenesis in an anomaly-free U(1) extension with higher-dimensional operators

We explore an anomaly-free U(1) gauge extended beyond the Standard model (BSM) framework, to account for the baryon asymmetry of the Universe, along with arranging for tiny neutrino mass. Neutrino masses are generated via higher-dimensional operators (HDOs) involving three right-handed neutrinos (RHNs) with gauge charges (4, 4 and −5 respectively) and two BSM scalars. This is an attractive framework as it can accommodate a keV scale dark matter, with the lightest RHN being the candidate. The remaining two RHNs are quasi-degenerate at the TeV-scale, actively participating in the process of resonant leptogenesis through their decay governed by the same set of HDOs. The RHNs being at the TeV scale, make this framework relevant for studying flavored resonant leptogenesis. This TeV-scale resonant leptogenesis, after satisfying the neutrino oscillation data, leads to interesting predictions on the Yukawa sector of the model. The thermal evolution of the baryon asymmetry has followed the experimental results rather accurately in that corner of parameter space. As a matter of fact, this TeV-scale framework which in principle relies on the low scale resonant leptogenesis typically leads to predictions that potentially can be tested at the colliders. In particular, we consider the same-sign dilepton signature that arises from the RHN pair production through the decay of heavy gauge boson of the extra U(1).