The smallness of neutrino mass, the strong CP problem, and the existence of dark matter are explained in an economical way. The neutrino mass is generated by the colored version of a radiative seesaw mechanism by using color adjoint mediators. The Majorana mass term of the adjoint fermion, which carries lepton number U(1)_L, is induced by its spontaneous breaking, resulting in a Majoron which doubles as the QCD (quantum chromodynamics) axion, thereby solving the strong CP problem. The breaking of U(1)_L sets simultaneously the seesaw scale for neutrino mass and the Peccei-Quinn breaking scale. This axion is a good candidate for dark matter as usually assumed.
The generation of neutrino masses by inverse seesaw mechanisms has advantages over other seesaw models since the potential new physics can be produced at the TeV scale. We propose a model that generates the inverse seesaw mechanism via spontaneous breaking of the lepton number, by extending the Standard Model with two scalar singlets and two fermion singlets both charged under lepton number. The model gives rise to a massless Majoron and a massive pseudoscalar which we dub as massive Majoron, which corresponds to the Nambu-Goldstone boson of the breaking of lepton number. If the massive Majoro…
We present singlet-Majoron couplings to Standard Model particles through two loops at leading order in the seesaw expansion, including couplings to gauge bosons as well as flavor-changing quark interactions. We discuss and compare the relevant phenomenological constraints on Majoron production as well as decaying Majoron dark matter. A comparison with standard seesaw observables in low-scale settings highlights the importance of searches for lepton-flavor-violating two-body decays $\ell \to \ell' +$Majoron in both the muon and tau sectors.
We propose an A_4 flavor-symmetric SU(3)xSU(2)xU(1) seesaw model where lepton number is broken spontaneously. A consistent two-zero texture pattern of neutrino masses and mixing emerges from the interplay of type-I and type-II seesaw contributions, with important phenomenological predictions. We show that, if the Majoron becomes massive, such seesaw scenario provides a viable candidate for decaying dark matter, consistent with cosmic microwave background lifetime constraints that follow from current WMAP observations. We also calculate the sub-leading one-loop-induced decay into photons which …
Majoron-driven spontaneous leptogenesis in type-II seesaw model
Korea Institute for Advanced Study（韩国高等科学研究院）；Institute for Basic Science (IBS)（基础科学研究院）；Tsung-Dao Lee Institute & School of Physics and Astronomy, Shanghai Jiao Tong University（上海交大李政道研究所与物理与天文学院）
We propose that inflation and dark matter have a common origin, connected to the neutrino mass generation scheme. As a model we consider spontaneous breaking of global lepton number within the seesaw mechanism. We show that it provides an acceptable inflationary scenario consistent with the recent CMB B-mode observation by the BICEP2 experiment. The scheme may also account for the baryon asymmetry of the Universe through leptogenesis for reasonable parameter choices.
We extend the singlet Majoron model of dark radiation by adding another singlet scalar of unit lepton charge. The spontaneous breaking of global $U(1)_L$ connects dark radiation with neutrino mass generation via the type-I seesaw mechanism. The model naturally has a stable scalar dark matter field. It also predicts the existence of a light scalar of mass less than 1 GeV that mixes with the Standard Model Higgs boson. We perform a numerical analysis of the parameters of the model by imposing constraints from giving correct relic abundance and satisfying bounds from direct dark matter detection,…
We perform a careful study of the neutral scalar sector of a model which includes a singlet, a doublet, and a triplet scalar field under $SU(2)$. This model is motivated by neutrino physics, since it is simply the most general version of the seesaw model of neutrino mass generation through spontaneous violation of lepton number. The neutral Higgs sector contains three CP-even and one massive CP-odd Higgs boson $A$, in addition to the massless CP-odd majoron $J$. The weakly interacting majoron remains massless if the breaking of lepton number symmetry is purely spontaneous. We show that the mas…
We consider the singlet Majoron model with softly broken lepton number. This model contains three right-handed neutrinos and a singlet scalar besides the standard model fields. The real part of the singlet scalar develops a vacuum expectation value to generate the lepton number violation for seesaw and leptogenesis. The imaginary part of the singlet scalar becomes a massive pseudo-Majoron to be a dark matter candidate with testability by colliders, direct detection experiments and neutrino observations.
Majorons are the Goldstone bosons of spontaneously broken lepton number and hence intimately connected to Majorana neutrino masses. Since all majoron couplings are heavily suppressed by the seesaw scale they are interesting candidates for long-lived dark matter. The signature decay into two mono-energetic neutrinos is potentially detectable with neutrino detectors for majoron masses above MeV and complementary to the loop-induced decays into visible particles. The mass range between keV and MeV can only be probed indirectly with the majoron decay into two photons; keV-scale majorons can be war…
We compute the effective coupling of the Majoron to W bosons at $\cO(\hbar)$ by evaluating the matrix element of the (B-L) current between the vacuum and a $W^+W^-$ state. The (B-L) anomaly vanishes, but the amplitude does not vanish as a result of a UV finite and non-local contribution which is entirely due to the mixing between left-chiral and right-chiral neutrinos. The result shows how anomaly-like couplings may arise in spite of the fact that the (B-L) current remains exactly conserved to all orders in $\hbar$, lending additional support to our previous proposal to identify the Majoron wi…
The Standard Model(SM) vacuum is unstable for the measured values of the top Yukawa coupling and Higgs mass. Here we study the issue of vacuum stability when neutrino masses are generated through spontaneous low-scale lepton number violation. In the simplest dynamical inverse seesaw, the SM Higgs has two siblings: a massive CP-even scalar plus a massless Nambu-Goldstone boson, called majoron. For TeV scale breaking of lepton number, Higgs bosons can have a sizeable decay into the invisible majorons. We examine the interplay and complementarity of vacuum stability and perturbativity restriction…
We examine the simplest realization of the linear seesaw mechanism within the Standard Model gauge structure. Besides the standard scalar doublet, there are two lepton-number-carrying scalars, a nearly inert SU2 doublet and a singlet. Neutrino masses result from the spontaneous violation of lepton number, implying the existence of a Nambu-Goldstone boson. Such "majoron" would be copiously produced in stars, leading to stringent astrophysical constraints. We study the profile of the Higgs bosons in this model, including their effective couplings to the vector bosons and their invisible decay br…
We discuss limits on neutrino-Majoron couplings both from laboratory experiments as well as from astrophysics. They apply to the simplest class of Majoron models which covers a variety of possibilities where neutrinos acquire mass either via a seesaw-type scheme or via radiative corrections. By adopting a general framework including CP phases we generalize bounds obtained previously. The combination of complementary bounds enables us to obtain a highly non-trivial exclusion region in the parameter space. We find that the future double beta project GENIUS, together with constraints based on sup…
How to Identify a Majoron: Effective Field Theories of Spontaneous Lepton Number Breaking
Università di Genova（热那亚大学）；INFN, Sezione di Genova（意大利国家核物理研究所热那亚分部）；Universidad Autónoma de Madrid（马德里自治大学）；Instituto de Física Teórica UAM/CSIC（UAM/CSIC理论物理研究所）
The singlet majoron model of seesaw neutrino mass is appended by one dark Majorana fermion singlet $χ$ with $L=2$ and one dark complex scalar singlet $ζ$ with $L=1$. This simple setup allows $χ$ to obtain a small radiative mass anchored by the same heavy right-handed neutrinos, whereas the one-loop decay of the standard-model Higgs boson to $χχ+ \barχ \barχ$ provides the freeze-in mechanism for $χ$ to be the light dark matter of the Universe.
We show that for a relatively light majoron ($\ll 100 $ eV) non-thermal production from topological defects is an efficient production mechanism. Taking the type I seesaw as benchmark scheme, we estimate the primordial majoron abundance and determine the required parameter choices where it can account for the observed cosmological dark matter. The latter is consistent with the scale of unification. Possible direct detection of light majorons with future experiments such as PTOLEMY and the formation of boson stars from the majoron dark matter are also discussed.
In some dark matter models, the coupling of the dark matter particle to the standard model Higgs determines the dark matter relic density while it is also consistent with dark matter direct detection experiments. On the other hand, the seesaw for generating the neutrino masses probably arises from a spontaneous symmetry breaking of global lepton number. The dark matter particle thus can significantly annihilate into massless Majorons when the lepton number breaking scale and hence the seesaw scale is near the electroweak scale. This leads to an interesting interplay between neutrino physics an…
We propose a simple model of spontaneous lepton number violation with potentially large flavor violating decays, including the possibility that majoron emitting decays, such as $μ\to e \, J$, saturate the experimental bounds. In this model the majoron is a singlet-doublet admixture. It generates a type-I seesaw for neutrino masses and contains also a vector-like lepton. As a by-product, the model can explain the anomalous $(g-2)_μ$ in parts of its parameter space, where one expects that the branching ratio of the Higgs to muons is changed with respect to Standard Model expectations. However, t…
A new Majoron model is presented within the framework of the seesaw mechanism. Its Higgs sector consists of only doublet representations and the lepton-number violation takes place at the same scale of the electroweak symmetry breaking. This model is different from the singlet- or triplet-Majoron model in several respects: it is free from the \(ρ\)-parameter constraint and it provides moderately fast neutrino decay, but the constraint from the stellar cooling of red giants is satisfied only with an imposed approximate symmetry. A \(τ\) neutrino as heavy as 10 MeV is possible in this model desp…
An attractive way to generate neutrino masses as required to account for current neutrino oscillation data involves the spontaneous breaking of lepton number. The resulting majoron may pick up a mass due to gravity. If its mass lies in the kilovolt scale, the majoron can play the role of late-decaying Dark Matter (LDDM), decaying mainly to neutrinos. In general the majoron has also a sub-dominant decay to two photons leading to a mono-energetic emission line which can be used as a test of the LDDM scenario. We compare expected photon emission rates with observations in order to obtain model in…
Neutrino masses may arise from spontaneous breaking of ungauged lepton number. Due to quantum gravity effects the associated Goldstone boson - the majoron - will pick up a mass. We determine the lifetime and mass required by cosmic microwave background observations so that the massive majoron provides the observed dark matter of the Universe. The majoron DDM scenario fits nicely in models where neutrino masses arise a la seesaw, and may lead to other possible cosmological implications.
We implement the seesaw mechanism in the 3-3-1 model with right-handed neutrinos. This is accomplished by the introduction of a scalar sextet into the model and the spontaneous violation of the lepton number. We identify the Majoron as a singlet under $SU_L(2)\otimes U_Y(1)$ symmetry, which makes it safe under the current bounds imposed by electroweak data. The main result of this work is that the seesaw mechanism works already at TeV scale with the outcome that the right-handed neutrino masses lie in the electroweak scale, in the range from MeV to tens of GeV. This window provides a great opp…
We investigate the production of primordial Gravitational Waves (GWs) arising from First Order Phase Transitions (FOPTs) associated to neutrino mass generation in the context of type-I and inverse seesaw schemes. We examine both "high-scale" as well as "low-scale" variants, with either explicit or spontaneously broken lepton number symmetry $U(1)_L$ in the neutrino sector. In the latter case, a pseudo-Goldstone majoron-like boson may provide a candidate for cosmological dark matter. We find that schemes with softly-broken $U(1)_L$ and with single Higgs-doublet scalar sector lead to either no F…
Neutrino mass generation through the Higgs mechanism not only suggests the need to reconsider the physics of electroweak symmetry breaking from a new perspective, but also provides a new theoretically consistent and experimentally viable paradigm. We illustrate this by describing the main features of the electroweak symmetry breaking sector of the simplest type-II seesaw model with spontaneous breaking of lepton number. After reviewing the relevant "theoretical" and astrophysical restrictions on the Higgs sector, we perform an analysis of the sensitivities of Higgs boson searches at the ongoin…
General flavor changing interactions for a Goldstone boson (GB) to fermions due to a spontaneous global $U(1)_G$ symmetry breaking are discussed. This GB may be the Axion, solving the strong QCD CP problem, if there is a QCD anomaly for the $U(1)_G$ charge assignments for quarks. Or it may be the Majoron in models from lepton number violation in producing seesaw Majorana neutrino masses if the symmetry breaking scale is much higher than the electroweak scale. It may also, in principle, play the roles of Axion and Majoron simultaneously as far as providing solution for the strong CP problem and…
We propose that neutrino masses are "seeded" by a dark sector within the inverse seesaw mechanism. This way we have a new, "hidden", variant of the scotogenic scenario for radiative neutrino masses. We discuss both explicit and dynamical lepton number violation. In addition to invisible Higgs decays with majoron emission, we discuss in detail the pheneomenolgy of dark matter, as well as the novel features associated to charged lepton flavour violation, and neutrino physics.
We consider the inverse Seesaw scenario for neutrino masses with the approximate Lepton number symmetry broken dynamically by a scalar with Lepton number two. We show that the Majoron associated to the spontaneous symmetry breaking can alleviate the Hubble tension through its contribution to $ΔN_\text{eff}$ and late decays to neutrinos. Among the additional fermionic states required for realizing the inverse Seesaw mechanism, sterile neutrinos at the keV-MeV scale can account for all the dark matter component of the Universe if produced via freeze-in from the decays of heavier degrees of freed…
Neutrino decay in the minimal seesaw model containing three right handed neutrinos and a complex $SU(2)\times U(1)$ singlet Higgs in addition to the standard model fields is considered. A global horizontal symmetry $U(1)_H$ is imposed, which on spontaneous breaking gives rise to a Goldstone boson. This symmetry is chosen in a way that makes a) the contribution of heavy ($\leq$ MeV) majorana neutrinos to the neutrinoless double beta decay amplitude vanish and b) allows the heavy neutrino to decay to a lighter neutrino and the Goldstone boson. It is shown that this decay can occur at a rate much…
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 invisible Higgs decay, and…
Knowledge of the mechanism of neutrino mass generation would help understand a lot more about Lepton Number Violation (LNV), the cosmological evolution of the Universe, or the evolu tion of astronomical objects. Here we propose a verifiable and viable extension of the Standard model for neutrino mass generation, with a low-scale seesaw mechanism via LNV condensation in the sector of sterile neutrinos. To prove the concept, we analyze a simplified model of just one single family of elementary particles and check it against a set of phenomenological constraints coming from electroweak symmetry b…
It is assumed, that there are two scales in quantum gravity. Metric fluctuates at the scales of the order of the Plank mass. The second scale $M_T$ is related to the fluctuations of torsion. We suppose, that it may be as low as $M_T \sim 1$ TeV. Due to the non - minimal coupling to torsion the attractive interaction between the fermions appears. The non - minimal coupling admits the appearance of different coupling constants for different fermions. This opens the possibility that the interaction with torsion gives the Majorana masses for the right - handed neutrinos (that are assumed to be of …
We propose a singlet majoron model that defines an inverse seesaw mechanism in the $ν$ sector. The majoron $ϕ$ has a mass $m_ϕ\approx 0.5$ eV and a coupling to the $τ$ lepton similar to the one to neutrinos. In the early universe it is initially in thermal equilibrium, then it decouples at $T\approx 500$ GeV and contributes with just $ΔN_{\rm eff}=0.026$ during BBN. At $T=26$ keV (final stages of BBN) a primordial magnetic field induces resonant $γ\leftrightarrow ϕ$ oscillations that transfer 6% of the photon energy into majorons, implying $ΔN_{\rm eff}=0.55$ and a 4.7% increase in the baryon …
The existence of right-handed neutrinos follows from theoretical consistence of the recently suggested electroweak symmetry breaking model, based on dynamical flavor gauge symmetry breaking. Only finite number of versions of the model exists. They differ by the number and the flavor structure of the right-handed neutrinos. We choose for inspection one of them, the non-minimal version with right-handed neutrinos in sextet flavor representation, and at some points we compare it with the minimal version. We show that a Majorana pairing of the sextet right-handed neutrinos is responsible for the f…
Small realistic Majorana neutrino masses can be generated via a Higgs triplet $(ξ^{++}, ξ^+, ξ^0)$ without having energy scales larger than $M_*={\cal O}(1)$ TeV in the theory. The large effective mass scale $Λ$ in the well-known seesaw neutrino-mass operator $Λ^{-1} (LLΦΦ)$ is naturally obtained with $Λ\sim M_*^2/μ,$ where $μ$ is a {\it small} scale of lepton-number violation. In theories with large extra dimensions, the smallness of $μ$ is naturally obtained by the mechanism of ``shining'' if the number of extra dimensions $n\ge 3.$ We study here the Higgs phenomenology of this model, where …
Escaping Solar Capture: Majoron mediated Elastic Dark Matter for the LZ 248~keV Event
Instituto de Física Corpuscular (IFIC), CSIC, Universitat de València（粒子物理研究所，西班牙科学委员会，巴伦西亚大学）；Indian Institute of Science Education and Research Bhopal（印度科学教育与研究学院博帕尔分校）
We show that spontaneous breaking of global $B-L$ symmetry responsible for small neutrino masses via the seesaw mechanism provides a unified picture of hybrid inflation and dark matter if the scale of $B-L$ breaking is close to the GUT scale. The majoron which acquires a small mass in the milli-eV range due to Planck scale breaking of $B-L$ is the dark matter candidate. The coupling of the majoron field to the neutrino induces a small violation of CPT and Lorentz invariance at the present epoch. We discuss some of the phenomenological and cosmological implications of the model.
The discovery of gravitational waves opens new opportunities to test BSM physics. In particular, the production of a stochastic background of primordial gravitational waves could provide a signature of the generation of the right-right Majorana neutrino mass term necessary, within type-I seesaw mechanism, to explain lightness of neutrinos and their mixing parameters. I will discuss the possibility that such a generation occurs during a strong first order phase transition within Majoron models [1]. As well known, this can indeed produce a stochastic background of gravitational waves. The scale …
The majoron, a pseudo-Goldstone boson arising from the spontaneous breaking of global lepton number, is a generic feature of many models intended to explain the origin of the small neutrino masses. In this work, we investigate potential imprints in the Cosmic Microwave Background (CMB) arising from massive majorons, should they thermalize with neutrinos after Big Bang Nucleosynthesis via inverse neutrino decays. We show that Planck2018 measurements of the CMB are currently sensitive to neutrino-majoron couplings as small as $λ\sim 10^{-13}$, which if interpreted in the context of the type-I se…
