Nonzero Neutrino Masses Research Articles

Loop-corrected Higgs masses in the NMSSM with inverse seesaw mechanism

In this study, we work in the framework of the Next-to-Minimal extension of the Standard Model (NMSSM) extended by six singlet leptonic superfields. Through the mixing with the three doublet leptonic superfields, the non-zero tiny neutrino masses can be generated through the inverse seesaw mechanism. While R-parity is conserved in this model lepton number is explicitly violated. We quantify the impact of the extended neutrino sector on the NMSSM Higgs sector by computing the complete one-loop corrections with full momentum dependence to the Higgs boson masses in a mixed on-shell-overline{text{ DR }} renormalization scheme, with and without the inclusion of CP violation. The results are consistently combined with the dominant two-loop corrections at mathcal{O}(alpha _t(alpha _s+alpha _t)) to improve the predictions for the Higgs mixing and the loop-corrected masses. In our numerical study we include the constraints from the Higgs data, the neutrino oscillation data, the charged lepton flavor-violating decays l_i rightarrow l_j + gamma , and the new physics constraints from the oblique parameters S, T, U. We present in this context the one-loop decay width for l_i rightarrow l_j + gamma . The loop-corrected Higgs boson masses are included in the Fortran code NMSSMCALC-nuSS.

Dark Matter and (g - 2) μ,e in radiative Dirac neutrino mass models

The origin of neutrino mass is a mystery, so is its nature, namely, whether neutrinos are Dirac or Majorana particles. On top of that, hints of large deviations of the muon and the electron anomalous magnetic moments (AMMs) are strong evidence for physics beyond the Standard Model. In this work, piecing these puzzles together, we propose a class of radiative Dirac neutrino mass models to reconcile (g - 2) μ,e anomalies with neutrino oscillation data. In this framework, a common set of new physics (NP) states run through the loops that generate non-zero neutrino mass and, due to chiral enhancement, provide substantial NP contributions to lepton AMMs. In addition, one of the three models studied in this work offers a Dark Matter candidate automatically stabilized by the residual symmetry, whose phenomenology is non-trivially connected to the other two puzzles mentioned above. Finally, our detailed numerical analysis reveals a successful resolution to these mysteries while being consistent with all colliders and cosmological constraints.

Pseudoscalar sterile neutrino self-interactions in light of Planck, SPT and ACT data

We reassess the viability of a cosmological model including a fourth additional sterile neutrino species that self-interacts through a new pseudoscalar degree of freedom.We perform a series of extensive analyses fitting various combinations of cosmic microwave background (CMB) data from Planck, the Atacama Cosmology Telescope (ACT) and the South Pole Telescope (SPT), both alone and in combination with Baryon Acoustic Oscillation (BAO) and Supernova Ia (SnIa) observations.We show that the scenario under study, although capable to resolve the Hubble tension without worsening the so-called S_8 tension about the growth of cosmic structures, is severely constrained by high-multipole polarization data from both Planck and SPT.Intriguingly, when trading Planck TE-EE data for those from ACT, we find a ≳ 3σ preference for a non-zero sterile neutrino mass, ms = 3.6+1.1 0.6 eV (68% C.L.), compatible with the range suggested by longstanding short-baseline (SBL) anomalies in neutrino oscillation experiments. The pseudoscalar model provides indeed a better fit to ACT data compared to ΛCDM (Δχ2 ≃ -5, ΔAIC = -1.3), although in a combined analysis with Planck the ΛCDM model is still favoured, as the preference for a non-zero sterile neutrino mass is mostly driven by ACT favouring a higher value for the primordial spectral index ns with respect to Planck. We show that the mild tension between Planck and ACT is due to the different pattern in the TE and EE power spectra on multipoles between 350 ≲ ℓ ≲ 1000.We also check the impact of marginalizing over the gravitational lensing information in Planck data, showing that the model does not solve the CMB lensing anomaly.Future work including higher precision data from current and upcoming CMB ground-based experiments will be crucial to test these results.

Singlet-doublet self-interacting dark matter and radiative neutrino mass

Self-interacting dark matter (SIDM) with a light mediator is a promising scenario to alleviate the small-scale problems of the cold dark matter paradigm while being consistent with the latter at large scales, as suggested by astrophysical observations. This, however, leads to an underabundant SIDM relic due to large annihilation rates into mediator particles, often requiring an extension of the simplest thermal or nonthermal relic generation mechanism. In this work, we consider a singlet-doublet fermion dark matter scenario where the singlet fermion with a light scalar mediator gives rise to the velocity-dependent dark matter self-interaction through a Yukawa type attractive potential. The doublet fermion, by virtue of its tiny mixing with the singlet, can be long-lived and can provide a nonthermal contribution to the singlet relic at late epochs, filling the deficit in the thermal relic of singlet SIDM. The light scalar mediator, due to its mixing with the standard model Higgs, paves the path for detecting such SIDM at terrestrial laboratories leading to constraints on model parameters from CRESST-III and XENON1T experiments. Enlarging the dark sector particles by two more singlet fermions and one scalar doublet, all odd under an unbroken ${\mathcal{Z}}_{2}$ symmetry can also explain nonzero neutrino mass in scotogenic fashion.

An extended 3-3-1 model with radiative linear seesaw mechanism

Motivated by the recent muon anomalous magnetic moment (g-2) measurement at FERMILAB and non-zero neutrino masses, we propose a model based on the SU(3)C×SU(3)L×U(1)X (3-3-1) gauge symmetry. The most popular 3-3-1 models in the literature require the presence of a scalar sextet to address neutrino masses. In our work, we show that we can successfully implement an one-loop linear seesaw mechanism with right-handed neutrinos, and vector-like fermions to nicely explain the active neutrino masses, and additionally reproduce the recent Muon g-2 result, in agreement with existing bounds.

One-loop matching of the type-II seesaw model onto the Standard Model effective field theory

In this paper, we continue to construct the low-energy effective field theories (EFTs) of the canonical seesaw models, which are natural extensions of the Standard Model (SM) to accommodate tiny but nonzero neutrino masses. Different from three right-handed neutrino singlets in the type-I seesaw model, the Higgs triplet in the type-II seesaw model participates directly in the electroweak gauge interactions, rendering the EFT construction more challenging. By integrating out the heavy Higgs triplet in the functional-integral formalism, we carry out a complete one-loop matching of the type-II seesaw model onto the so-called Standard Model Effective Field Theory (SMEFT). It turns out that 41 dimension-six operators (barring flavor structures and Hermitian conjugates) in the Warsaw basis of the SMEFT can be obtained, covering all those 31 dimension-six operators in the case of type-I seesaw model. The Wilson coefficients for 41 dimension-six operators are computed up to mathcal{O}left({M}_{Delta }^{-2}right) with M∆ being the mass scale of the Higgs triplet. Moreover, the branching ratios of rare radiative decays of charged leptons {l}_{alpha}^{-}to {l}_{beta}^{-}+gamma are calculated in the EFT and compared with that in the full theory in order to demonstrate the practical application and the correctness of our EFT construction.

Constraining the axion mass from the nonobservation of 0νββ decay

In this paper, we study the interaction of neutrinos with nonrelativistic axions. Axions are low-mass neutral bosons whose existence has been proposed long ago by Peccei and Quinn to explain the spontaneous breaking of the CP symmetry in the early Universe. We treat them as pseudoscalar particles, which could be one of the constituents of cold DM. The interactions between axions and neutrinos might be a possible mechanism to explain for nonzero neutrino masses. Here on, we present an analysis which combines the limits for the neutrino masses extracted from the nonobservation of the neutrinoless double beta ([Formula: see text]) decay with the ones corresponding to the coupling between axions and neutrinos. We begin by defining the neutrino–axion interactions, then we extract the values of both the axion and neutrino masses by taking from the literature representative values of the strength of the couplings and of the matrix elements of the operators participating in the currents.

Doubly charged scalars and vector-like leptons confronting the muon g-2 anomaly and Higgs vacuum stability

The present work introduces new scalar and fermionic degrees of freedom to the Standard Model. While the scalar sector is augmented by a complex scalar triplet and a doubly charged scalar singlet, the fermionic sector is extended by two copies of vector-like leptons. Of these, one copy is an $SU(2)_L$ singlet while the other, an $SU(2)_L$ doublet. We explain how this combination can offer a solution to the muon g-2 anomaly and also lead to non-zero neutrino masses. In addition, it is also shown that the parameter regions compliant with the two aforementioned issues can stabilise the electroweak vacuum till the Planck scale, something not possible within the Standard Model alone.

Phenomenological study of type II seesaw with Δ(27) symmetry

We discuss the phenomenology of type-II seesaw by extending the standard model with additional Higgs doublets, scalar triplets as well as a scalar singlet invoked with discrete flavor symmetry Δ(27), for the explanation of non-zero neutrino masses and mixing, matter–antimatter asymmetry, and lepton flavor violation (LFV). The light neutrino masses can be obtained via type-II seesaw mechanism by transforming scalar triplets as 3 and scalar doublets as various singlet representations like 1 1 , 1 2 , 1 3 along with scalar singlet as 1 1 under Δ(27) symmetry. With the implementation of this discrete flavor symmetry Δ(27), we get simpler structure for light neutrino mass matrix, which helps in analyzing neutrino phenomenology analytically as well as numerically. We further demonstrate the detailed numerical analysis by scanning the input model parameters in agreement with neutrino oscillation data like non-zero reactor mixing angle (θ 13), CP-violating phase (δ CP), the sum of the light neutrino masses, two mass squared differences, and its implication to neutrino-less double beta decay. The model also explains the matter–antimatter asymmetry of the Universe through resonant leptogenesis with the decay of TeV scale scalar triplets and variation of CP-asymmetry with input model parameters. Finally, we comment on the implication to LFV decays like μ → eγ, μ → 3e processes via the mediation of these TeV scale scalar triplets. We have studied collider physics briefly.

Three-body decays of heavy Dirac and Majorana fermions

Nonzero neutrino masses imply the existence of degrees of freedom and interactions beyond those in the Standard Model. A powerful indicator of what these might be is the nature of the massive neutrinos: Dirac fermions versus Majorana fermions. While addressing the nature of neutrinos is often associated with searches for lepton-number violation, there are several other features that distinguish Majorana from Dirac fermions. Here, we compute in great detail the kinematics of the daughters of the decays into charged-leptons and neutrinos of hypothetical heavy neutral leptons at rest. We allow for the decay to be mediated by the most general four-fermion interaction Lagrangian. We demonstrate, for example, that when the daughter charged-leptons have the same flavor or the detector is insensitive to their charges, polarized Majorana-fermion decays have zero forward-backward asymmetry in the direction of the outgoing neutrino (relative to the parent spin), whereas Dirac-fermion decays can have large asymmetries. Going beyond studying forward-backward asymmetries, we also explore the fully differential width of the three-body decays. It contains a wealth of information not only about the nature of the new fermions but also the nature of the interactions behind their decays.

Neutrino mass, leptogenesis and sterile neutrino dark matter in inverse seesaw framework

We study [Formula: see text] flavor symmetric inverse seesaw model which has the possibility of simultaneously addressing neutrino phenomenology, dark matter (DM) and baryon asymmetry of the universe (BAU) through leptogenesis. The model is the extension of the standard model by the addition of two (RH) neutrinos and three sterile fermions leading to a keV scale sterile neutrino DM and two pairs of quasi-Dirac states. The CP violating decay of the lightest quasi-Dirac pair present in the model generates lepton asymmetry which then converts to BAU. Thus, this model can provide a simultaneous solution for nonzero neutrino mass, DM content of the universes and the observed baryon asymmetry. The [Formula: see text] flavor symmetry in this model is augmented by additional [Formula: see text] symmetry to constrain the Yukawa Lagrangian. A detailed numerical analysis has been carried out to obtain DM mass, DM-active mixing as well as BAU both for normal hierarchy as well as inverted hierarchy. We try to correlate the two cosmological observables and found a common parameter space satisfying the DM phenomenology and BAU. The parameter space of the model is further constrained from the latest cosmological bounds on the observables.

Light neutrino masses from gravitational condensation: the Schwinger\u2013Dyson approach

In this work we demonstrate that non-zero neutrino masses can be generated from gravitational interactions. We solve the Schwinger–Dyson equations to find a non-trivial vacuum thereby determining the neutrino condensate scale and the number of new particle degrees of freedom required for gravitationally induced dynamical chiral symmetry breaking. We show for minimal beyond the Standard Model particle content, the scale of the condensation occurs close to the Planck scale.

Emergent Dark Energy, neutrinos and cosmological tensions

The Phenomenologically Emergent Dark Energy model, a dark energy model with the same number of free parameters as the flat $\Lambda$CDM, has been proposed as a working example of a minimal model which can avoid the current cosmological tensions. A straightforward question is whether or not the inclusion of massive neutrinos and extra relativistic species may spoil such an appealing phenomenological alternative. We present the bounds on $M_{\nu}$ and $N_{\rm eff}$ and comment on the long standing $H_0$ and $\sigma_8$ tensions within this cosmological framework with a wealth of cosmological observations. Interestingly, we find, at $95\%$ confidence level, and with the most complete set of cosmological observations, $M_{\nu}\sim 0.21^{+0.15}_{-0.14}$ eV and $N_{\rm eff}= 3.03\pm 0.32$ i.e. an indication for a non-zero neutrino mass with a significance above $2\sigma$. The well known Hubble constant tension is considerably easened, with a significance always below the $2\sigma$ level.

Searching for New Physics in Two-Neutrino Double Beta Decay.

Motivated by nonzero neutrino masses and the possibility of new physics discovery, a number of experiments search for neutrinoless double beta decay. While hunting for this hypothetical nuclear process, a significant amount of two-neutrino double beta decay data have become available. Although these events are regarded and studied mostly as the background of neutrinoless double beta decay, they can also be used to probe physics beyond the standard model. In this Letter, we show how the presence of right-handed leptonic currents would affect the energy distribution and angular correlation of the outgoing electrons in two-neutrino double beta decay. Consequently, we estimate constraints imposed by currently available data on the existence of right-handed neutrino interactions without having to assume their nature. In this way, our results complement the bounds coming from the nonobservation of neutrinoless double beta decay as they limit also the exotic interactions of Dirac neutrinos. We perform a detailed calculation of two-neutrino double beta decay under the presence of exotic (axial-) vector currents, and we demonstrate that current experimental searches can be competitive to existing limits.

Revamped Bi-large neutrino mixing with Gatto-Sartori-Tonin like relation

The Gatto Sartori Tonin (GST) relation which connects the Cabibbo angle and the quark mass ratio: θC=md/ms, is instituted as θ13=m1/m3 to a Bi-large motivated lepton mixing framework that relies on the unification of mixing parameters: θ13=θC and θ12=θ23. This modification, in addition to ruling out the possibility of vanishing θ13, advocates for a nonzero lowest neutrino mass and underlines the normal ordering of the neutrino masses. The framework is further enhanced by the inclusion of a charged lepton diagonalizing matrix UlL with (θ12l∼θC). The model is framed at the Grand unification theory (GUT) scale. To understand the universality of the GST relation and the Cabibbo angle, we test the observational mixing parameters at the Z boson mass scale.

Elementary Charge and Neutrino’s Mass from Planck Length

It is shown that the postulation of a minimum length for the horizons of a black hole leads to lower bounds for the electric charges and magnetic moments of elementary particles. If the minimum length has the order of the Planck scale, these bounds are given, respectively, by the electronic charge and by $\mu \sim 10^{-21} \mu_B$. The latter implies that the masses of fundamental particles are bounded above by the Planck mass, and that the smallest non-zero neutrino mass is $m_{\nu} \sim 10^{-2}$eV. A precise estimation in agreement to the area quantisation of Loop Quantum Gravity predicts a mass for the lightest massive state in concordance with flavor oscillation measurements, and a Barbero-Immirzi parameter in accordance to horizon entropy estimations.

What will it take to measure individual neutrino mass states using cosmology?

We study the impact of assumptions made about the neutrino mass ordering on cosmological parameter estimation with the purpose of understanding whether in the future it will be possible to infer the specific neutrino mass distribution from cosmological data. We find that although the commonly used assumption of a degenerate neutrino hierarchy is manifestly wrong and leads to changes in cosmological observables such as the cosmic microwave background and large scale structure compared to the correct (normal or inverted) neutrino hierarchy, the induced changes are so small that even with extremely optimistic assumptions about future data they will remain undetectable. We are thus able to conclude that while cosmology can probe the neutrino contribution to the cosmic energy density extremely precisely (and hence provide a detection of a non-zero total neutrino mass at high significance), it will not be possible to directly measure the individual neutrino masses.

Impact of neutrino decays on the supernova neutronization-burst flux

The discovery of non-zero neutrino masses invites one to consider decays of heavier neutrinos into lighter ones. We investigate the impact of two-body decays of neutrinos on the neutronization burst of a core-collapse supernova -- the large burst of $\nu_e$ during the first 25 ms post core-bounce. In the models we consider, the $\nu_e$, produced mainly as a $\nu_3\,(\nu_2)$ in the normal (inverted) mass ordering, are allowed to decay to $\nu_1\,(\nu_3)$ or $\bar{\nu}_1\,(\bar{\nu}_3)$, and an almost massless scalar. These decays can lead to the appearance of a neutronization peak for a normal mass ordering or the disappearance of the same peak for the inverted one, thereby allowing one mass ordering to mimic the other. Simulating supernova-neutrino data at the Deep Underground Neutrino Experiment (DUNE) and the Hyper-Kamiokande (HK) experiment, we compute their sensitivity to the neutrino lifetime. We find that, if the mass ordering is known, and depending on the nature of the Physics responsible for the neutrino decay, DUNE is sensitive to lifetimes $\tau/m \lesssim 10^6$ s/eV for a galactic SN sufficiently close-by (around 10 kpc), while HK is sensitive to lifetimes $\tau/m \lesssim 10^7$ s/eV. These sensitivities are far superior to existing limits from solar-system-bound oscillation experiments. Finally, we demonstrate that using a combination of data from DUNE and HK, one can, in general, distinguish between decaying Dirac neutrinos and decaying Majorana neutrinos.

Zero-deadtime processing in beta spectroscopy for measurement of the non-zero neutrino mass

The Project 8 collaboration seeks to measure, or more tightly bound, the mass of the electron antineutrino by applying a novel spectroscopy technique to precisely measure the tritium beta-decay spectrum. The current system produces a single analog signal, which is digitized and processed in several stages before being saved to local disk storage. Online processing includes two stages, an FPGA connected to the analog to digital converter reduces the data down to the region of interest before shipping over the local network for further processing and storage. A normal CPU-based processing stage applies triggering logic to only save data at times when a signal is present, further reducing the total volume of data which needs to be written to disk or transferred for long-term storage. The next stage of the project will need to process many input channels and will integrate a necessary aggregation and combination step prior to applying the event search and triggering logic. We present the online processing system which has successfully been deployed for the current, singlechannel, phase. We also present the status and design for a many-channel platform.

Higgs and BSM Studies at the LHC

The discovery and study of the Higgs boson at the Large Hadron Collider of CERN has proven the validity of the Brout–Englert–Higgs mechanism of mass creation in the standard model via spontaneous symmetry breaking. The new results obtained by the ATLAS and CMS Collaborations at the LHC show that all measured cross-sections agree within uncertainties with the predictions of the theory. However, the standard model has obvious difficulties (nonzero neutrino masses, hierarchy problem, existence of dark matter, non-existence of antimatter galaxies, etc.), which point towards more possible violated symmetries. We first summarize the present status of the studies of the Higgs boson, including the latest results at 13 TeV p-p collision energy, then enlist some of the problems with possible solutions and the experimental situation regarding them.