Search

Cosmic voids identified in the spatial distribution of galaxies provide complementary information to two-point statistics. In particular, constraints on the neutrino mass sum, ∑ m ν , promise to benefit from the inclusion of void statistics. We perform inference on the CMASS Northern Galactic Cap sample of the third-generation Sloan Digital Sky Survey/Baryon Oscillation Spectroscopic Survey (BOSS) with the aim of constraining ∑ m ν . We utilize the void size function, the void–galaxy cross power spectrum, and the galaxy auto power spectrum. To extract constraints from these summary statistics we use a simulation-based approach, specifically implicit likelihood inference. We populate approximate gravity-only, particle-neutrino cosmological simulations with an expressive halo occupation distribution model. With a conservative scale cut of k max = 0.15 h Mpc − 1 and a Planck-inspired Lambda cold dark matter prior, we find upper bounds on ∑ m ν of 0.43 and 0.35 eV from the galaxy auto power spectrum and the full data vector, respectively (95% credible interval). Relaxing the scale cut to k max = 0.2 h Mpc − 1 , we find 0.28 and 0.32 eV. Generally, void statistics appear to add modest but nonzero information beyond the auto power spectrum. We also substantiate the usual assumption that the void size function is Poisson distributed. [ABSTRACT FROM AUTHOR]

The large-scale structure of the Universe is distributed in a cosmic web. Studying the distribution and clustering of dark matter particles and haloes may open up a new horizon for studying the physics of the dark Universe. In this work, we investigate the nearest neighbour statistics and spherical contact function in cosmological models with massive neutrinos. For this task, we use the relativistic N -body code, gevolution, and study particle snapshots at three different redshifts. In each snapshot, we find the haloes and evaluate the letter functions for them. We show that a generic behaviour can be found in the nearest neighbour, G (r), and spherical contact functions, F (r), which makes these statistics promising tools to constrain the total neutrino mass. [ABSTRACT FROM AUTHOR]

Detecting neutrino-less double beta ( 0 ν β β ) decay with high-sensitivity 0 ν β β detectors is of current interest for studying the Majorana neutrino's nature, the neutrino mass (ν -mass), right-handed weak currents (RHCs), and others beyond the Standard Model. Many experimental groups have studied 0 ν β β decay with ν -mass sensitivities on the order of 100 meV and RHC sensitivities on the order of 10   − 9 –10   − 6 , but no clear 0 ν β β signals have been observed so far in these ν -mass and RHC regions. Thus, several experimental groups are developing higher-sensitivity detectors to explore a smaller ν -mass region around 15–50 meV, which corresponds to the inverted hierarchy ν -mass, and smaller RHC regions on the order of 10   − 10 –10   − 7 in the near future. Nuclear matrix elements (NMEs) for ν -mass and RHC processes are crucial for extracting the ν -mass and RHCs of particle physics interest from 0 ν β β experiments. This report briefly reviews detector sensitivities and upper limits on the ν -mass and right-handed currents for several current 0 ν β β detectors and the ν -mass and RHC sensitivities expected for some near-future ones. [ABSTRACT FROM AUTHOR]

I propose a unified model of particle physic and cosmology based on both a new extension of the standard particle model and the fundamental principle of the standard cosmology. Beyond the standard model, I introduce several species of dark fields with the dark symmetry of Z 2 ⊗ Z 2 ′ , the inflation field, cold dark matter (CDM) and dark energy (DE) are of course included among them. The model can coherently and completely describe the origin and evolution of the universe from the primordial inflation to the reheating, to the baryogenesis, to the current CDM and DE, and also the neutrino mass generation mechanism. For the energy evolution of each phase, I give its dynamical system of equations, and solve them by some special techniques. The numerical results can clearly show how each evolution is successfully implemented, furthermore, the model demonstrates that the DE genesis is purely from the CDM condensation, which is essentially a reverse process of the primordial slow-roll inflation, there is not the so-called "cosmological constant energy". By use of fewer input parameters, the model not only exactly reproduces the measured inflationary data and the current energy density budget, but also finely predicts such important values as the tensor-to-scalar ratio r 0. 0 5 ≈ 1. 6 8 × 1 0 − 6 , the inflaton mass M Φ ≈ 5. 0 5 × 1 0 1 0 GeV, the reheating temperature T r e ≈ 8. 2 9 × 1 0 1 0 GeV, the CDM mass M S ≈ 2 5 6 GeV, η B ≈ 6. 1 4 × 1 0 − 1 0 and h ≈ 0. 7 3 , in particular, the model smoothly clarifies and eliminates the "Hubble tension". In short, the unified model newly establishes the deeper and closer relations between particle physics and cosmology, therefore we expect the ongoing and future experiments to test the model. [ABSTRACT FROM AUTHOR]

Texture matrices are used to mitigate the redundancy inherent in the description of flavor physics via Yukawa couplings by eliminating some entries in order to identify relevant parameters. In this paper, the implications of a 2-zero texture mixing matrix in the parallel case are studied for leptons. Eight possible parametrizations were found and the parameter space was studied for all the scenarios using a chi-squared analysis. Using a model of GUT with S O (1 0) symmetry, the mass matrices were restricted and a reduction of parameters was possible by adding the previously proposed Universal Texture Constraint for two scenarios. Constrains on the mass of the heaviest neutrino were found and the interval favored by UTC is m ν 3 ≤ 0. 3 eV as well as general properties of the free parameters of the model. [ABSTRACT FROM AUTHOR]

Quark and lepton masses and mixings are considered in the framework of the microscopic model. The most general ansatz for the interactions among tetrons leads to a Hamiltonian HT$H_T$ involving Dzyaloshinskii‐Moriya (DM), Heisenberg and torsional isospin forces. Diagonalization of the Hamiltonian provides for 24 eigenvalues which are identified as the quark and lepton masses. While the masses of the third and second family arise from DM and Heisenberg type of isospin interactions, light family masses are related to torsional interactions among tetrons. Neutrino masses turn out to be special in that they are given in terms of tiny isospin non‐conserving DM, Heisenberg and torsional couplings. The approach not only leads to masses, but also allows to calculate the quark and lepton eigenstates, an issue, which is important for the determination of the CKM and PMNS mixing matrices. Compact expressions for the eigenfunctions of HT$H_T$ are given. The almost exact isospin conservation of the system dictates the form of the lepton states and makes them independent of all the couplings in HT$H_T$. As a consequence, a parameter‐free analytic expression for the PMNS matrix is derived which fits numerically all the measured matrix components. The formula includes a prediction of the leptonic Jarlskog invariant JPMNS=−0.0106$J_{PMNS}=-0.0106$. An outlook is given on the treatment of the CKM matrix. Quark and lepton masses and mixings are considered in the framework of the microscopic model. The most general ansatz for the interactions among tetrons leads to a Hamiltonian HT involving Dzyaloshinskii‐Moriya (DM), Heisenberg and torsional isospin forces. Diagonalization of the Hamiltonian provides for 24 eigenvalues which are identified as the quark and lepton masses. While the masses of the third and second family arise from DM and Heisenberg type of isospin interactions, light family masses are related to torsional interactions among tetrons. Neutrino masses turn out to be special in that they are given in terms of tiny isospin non‐conserving DM, Heisenberg and torsional couplings. The approach not only leads to masses, but also allows to calculate the quark and lepton eigenstates, an issue, which is important for the determination of the CKM and PMNS mixing matrices. Compact expressions for the eigenfunctions of HT are given. The almost exact isospin conservation of the system dictates the form of the lepton states and makes them independent of all the couplings in HT. As a consequence, a parameter‐free analytic expression for the PMNS matrix is derived which fits numerically all the measured matrix components. The formula includes a prediction of the leptonic Jarlskog invariant JPMNS = −0.0106. An outlook is given on the treatment of the CKM matrix. [ABSTRACT FROM AUTHOR]

Cosmology is poised to measure the neutrino mass sum M ν and has identified several smaller-scale observables sensitive to neutrinos, necessitating accurate predictions of neutrino clustering over a wide range of length scales. The FlowsForTheMasses non-linear perturbation theory for the the massive neutrino power spectrum, |$\Delta ^2_\nu (k)$|⁠ , agrees with its companion N -body simulation at the |$10~{{\ \rm per\ cent}}-15~{{\ \rm per\ cent}}$| level for k ≤ 1  h  Mpc−1. Building upon the Mira-Titan IV emulator for the cold matter, we use FlowsForTheMasses to construct an emulator for |$\Delta ^2_\nu (k)$|⁠ , Cosmic-Eν , which covers a large range of cosmological parameters and neutrino fractions Ων, 0 h 2 ≤ 0.01 (M ν ≤ 0.93 eV). Consistent with FlowsForTheMasses at the 3.5 per cent level, it returns a power spectrum in milliseconds. Ranking the neutrinos by initial momenta, we also emulate the power spectra of momentum deciles, providing information about their perturbed distribution function. Comparing a M ν = 0.15 eV model to a wide range of N -body simulation methods, we find agreement to 3 per cent for k ≤ 3 k FS = 0.17  h  Mpc−1 and to 19 per cent for k ≤ 0.4  h  Mpc−1. We find that the enhancement factor, the ratio of |$\Delta ^2_\nu (k)$| to its linear-response equivalent, is most strongly correlated with Ων, 0 h 2, and also with the clustering amplitude σ8. Furthermore, non-linearities enhance the free-streaming-limit scaling |$\partial \log (\Delta ^2_\nu /\Delta ^2_{\rm m}) / \partial \log (M_\nu)$| beyond its linear value of 4, increasing the M ν-sensitivity of the small-scale neutrino density. [ABSTRACT FROM AUTHOR]

Long-baseline neutrino experiments represent the optimal platforms for probing the lepton Yukawa sector of the Standard Model, and significant experiments are either under construction or in the planning stages. This review delves into the scientific motivations behind these facilities, which stem from the pivotal 2012 discovery of the θ 13 mixing angle. We provide an overview of the two ongoing projects, DUNE and HyperKamiokande, detailing their physics potential and the technical hurdles they face. Furthermore, we briefly examine proposals for forthcoming endeavors and innovative concepts that could push beyond conventional Superbeam technology. [ABSTRACT FROM AUTHOR]

The oscillations of ultra-relativistic neutrinos are realized by the propagation of assumed zero-mass on-shell neutrinos with the speed of light in vacuum combined with the phase modulation by the small mass term exp [ - i (m ν k 2 / 2 | p → |) τ ] with a time parameter τ . This picture is realized in the first quantization by the mass expansion and in field theory by the use of δ (x 0 - y 0 - τ) ⟨ 0 | T ⋆ ν Lk (x) ν Lk (y) ¯ | 0 ⟩ with the neutrino mass eigenstates ν Lk and a finite positive τ after the contour integral of the propagating neutrino energies. By noting that the conventional detectors are insensitive to neutrino masses, the measured energy-momenta of the initial and final states with assumed zero-mass neutrinos are conserved. The propagating neutrinos preserve the three-momentum in this sense but the energies of the massive neutrinos are conserved up to uncertainty relations and thus leading to oscillations. Conceptual complications in the case of Majorana neutrinos due to the charge conjugation in d = 4 are also discussed. [ABSTRACT FROM AUTHOR]

The KArlsruhe TRItium Neutrino experiment (KATRIN) aims to determine the effective mass of the electron antineutrino via a high-precision measurement of the tritium β -decay spectrum in its end-point region. The target neutrino-mass sensitivity of 0.2 eV / c 2 at 90% CL can only be achieved in the case of high statistics and good control of the systematic uncertainties. One key systematic effect originates from the calculation of the molecular final states of T 2 β decay. In the first neutrino-mass analyses of KATRIN the contribution of the uncertainty of the molecular final-states distribution (FSD) was estimated via a conservative phenomenological approach to be 2 × 10 - 2 eV 2 / c 4. In this work a new procedure is presented for estimating the FSD-related uncertainties by considering the details of the final-states calculation, i.e. the uncertainties of constants, parameters, and functions used in the calculation as well as its convergence itself as a function of the basis-set size used in expanding the molecular wave functions. The calculated uncertainties are directly propagated into the experimental observable, the squared neutrino mass m ν 2 , and thus have to be determined individually for each experimental configuration. For the experimental conditions of the first KATRIN measurement campaign the new procedure is presented in detail, allowing for the application of this procedure to other experiments. This specific calculation leads to a constraint of the FSD-related uncertainty of 1.3 × 10 - 3 eV 2 / c 4 , well below the design limit of 7.5 × 10 - 3 eV 2 / c 4 for any individual systematic contribution. [ABSTRACT FROM AUTHOR]

In the model [J. Ganguly and R. S. Hundi, Chinese Phys. C 46, 103101 (2022).], the neutrino mixing has been explained in a type II seesaw scenario with generalized CP symmetries. The neutrino mass matrix has μ − τ symmetric nature. As neutrino oscillation data suggests neutrino mixing can deviate from μ − τ symmetry, in this work, deviation from μ − τ symmetric mass matrix is shown by breaking the generalized CP symmetry explicitly by a small amount in the Yukawa Lagrangian which actually shows that atmospheric mixing angle can deviate from maximal value. As a phenomenological implication, branching ratios of the lepton flavor violating decays have been studied, which occurs by the triplet Higgs, by writing down the full scalar potential and then finding the mass eigenstates of the scalars. We have studied the implications of neutrinoless double beta decay within our model. [ABSTRACT FROM AUTHOR]

The strong mass hierarchy, flavor mixing pattern and CP violation in the quark sector have been long-standing puzzles in the Standard Model. Thanks to the elegant neutrino oscillation experiments in the past few decades, now we know that neutrinos are massive and lepton flavor mixing is significant. The flavor puzzles have extended to the lepton sector. In this article, we explain how the idea of texture zeros applies to understand lepton flavor mixing, and emphasize that it is particularly useful for exploring the underlying dynamics or symmetries for lepton flavor mixing. [ABSTRACT FROM AUTHOR]

Weak lensing of the cosmic microwave background is rapidly emerging as a powerful probe of neutrinos, dark energy, and new physics. We present a fast computation of the non-linear CMB lensing power spectrum that combines non-linear perturbation theory at early times with power spectrum emulation using cosmological simulations at late times. Comparing our calculation with light-cones from the FLAMINGO 5.6 Gpc cube dark-matter-only simulation, we confirm its accuracy to |$1{{\ \rm per\ cent}}$| (⁠|$2{{\ \rm per\ cent}}$|⁠) up to multipoles L  = 3000 (L  = 5000) for a νΛCDM cosmology consistent with current data. Clustering suppression due to small-scale baryonic phenomena such as feedback from active galactic nuclei can reduce the lensing power by |$\sim 10{{\ \rm per\ cent}}$|⁠. To our perturbation theory and emulator-based calculation, we add SP(k) , a new fitting function for this suppression, and confirm its accuracy compared to the FLAMINGO hydrodynamic simulations to |$4{{\ \rm per\ cent}}$| at L  = 5000, with similar accuracy for massive neutrino models. We further demonstrate that scale-dependent suppression due to neutrinos and baryons approximately factorize, implying that a careful treatment of baryonic feedback can limit biasing neutrino mass constraints. [ABSTRACT FROM AUTHOR]

We develop a grand unified theory of matter and forces based on the gauge symmetry SU(5)L × SU(5)R with parity interchanging the two factor groups. Our main motivation for such a construction is to realize a minimal GUT embedding of left-right symmetric models that provide a parity solution to the strong CP problem without the axion. We show how the gauge couplings unify with an intermediate gauge symmetry SU(3)cL × SU(2)2L × U(1)L × SU(5)R, and establish its consistency with proton decay constraints. The model correctly reproduces the observed fermion masses and mixings and leads to naturally light Dirac neutrinos with their Yukawa couplings suppressed by a factor MI/MG, the ratio of the intermediate scale to the GUT scale. We call this mechanism type II-Dirac seesaw. Furthermore, the model predicts δCP = ±(130.4±1.2)° and = (4.8 – 8.4) meV for the Dirac CP phase and the lightest neutrino mass. We demonstrate how the model solves the strong CP problem via parity symmetry. [ABSTRACT FROM AUTHOR]

At least two relics of the Big Bang have survived: the cosmological microwave background (CMB) and the cosmological neutrino background (C ν B). Being the second most abundant particle in the universe, the neutrino has a significant impact on its evolution from the Big Bang to the present day. Neutrinos affect the following cosmological processes: the expansion rate of the universe, its chemical and isotopic composition, the CMB anisotropy and the formation of the large-scale structure of the universe. Another relic neutrino background is theoretically predicted, it consists of non-equilibrium antineutrinos of Primordial Nucleosynthesis arising as a result of the decay of neutrons and tritium nuclei. Such antineutrinos are an indicator of the baryon asymmetry of the universe. In addition to experimentally detectable active neutrinos, the existence of sterile neutrinos is theoretically predicted to generate neutrino masses and explain their oscillations. Sterile neutrinos can also solve such cosmological problems as the baryonic asymmetry of the universe and the nature of dark matter. The recent results of several independent experiments point to the possibility of the existence of a light sterile neutrino. However, the existence of such a neutrino is inconsistent with the predictions of the Standard Cosmological Model. The inclusion of a non-zero lepton asymmetry of the universe and/or increasing the energy density of active neutrinos can eliminate these contradictions and reconcile the possible existence of sterile neutrinos with Primordial Nucleosynthesis, the CMB anisotropy, and also reduce the H0-tension. In this brief review, we discuss the influence of the physical properties of active and sterile neutrinos on the evolution of the universe from the Big Bang to the present day. [ABSTRACT FROM AUTHOR]

In the framework of quantum field theory, we analyze the neutrino oscillations in the presence of a torsion background. We consider the Einstein–Cartan theory and we study the cases of constant torsion and of linearly time-dependent torsion. We derive new neutrino oscillation formulae which depend on the spin orientation. Indeed, the energy splitting induced by the torsion influences oscillation amplitudes and frequencies. This effect is maximal for values of torsion of the same order of the neutrino masses and for very low momenta, and disappears for large values of torsion. Moreover, neutrino oscillation is inhibited for intensities of torsion term much larger than neutrino masses and momentum. The modifications induced by torsion on the C P -asymmetry are also presented. Future experiments, such as PTOLEMY, which have as a goal the analysis of the cosmological background of neutrino (which have very low momenta), can provide insights into the effect shown here. [ABSTRACT FROM AUTHOR]

This review provides a succinct overview of the basic aspects of neutrino physics. The topics covered include neutrinos in the standard model and the three-neutrino mixing scheme; the current status of neutrino oscillation measurements and what remains to be determined; the seesaw mechanisms for neutrino mass generation and the associated phenomenology, including the leptogenesis mechanism to explain the observed matter–antimatter asymmetry of the Universe; and models for the origin of the pattern of neutrino mixing and lepton masses based on discrete flavour symmetries and modular invariance. [ABSTRACT FROM AUTHOR]

The H 0 tension stands as a prominent challenge in cosmology, serving as a primary driver for exploring alternative models of dark energy. Another tension arises from measurements of the S 8 parameter, which is characterize the amplitude of matter fluctuations in the universe. In this study, we address the alleviation of both the Hubble tension and S 8 tension by incorporating Kaniadakis horizon entropy. We investigate two scenarios to explore the impact of this entropy on cosmological parameters. In the first scenario, utilizing modified Friedmann equations through Kaniadakis entropy, we estimate the values of H 0 and S 8 . In the subsequent scenario, we introduce the neutrino term and assess its effect on mitigating the Hubble and S 8 tensions. Our findings reveal that when considering the first scenario, the results closely align with Planck's 2018 outcomes for Hubble and S 8 tensions. Moreover, with the inclusion of neutrinos, these tensions are alleviated to approximately 2 σ , and the S 8 value is in full agreement with the results from the KiDS and DES survey. Furthermore, we impose a constraint on the parameter K in each scenario. Our analysis yields K = 0.12 ± 0.41 for Kaniadakis entropy without neutrinos and K = 0.39 ± 0.4 for the combined dataset considering Kaniadakis entropy in the presence of neutrinos. We demonstrate that the value of K may be affected by neutrino mass, which can cause energy transfer between different parts of the universe and alter the Hubble parameter value. [ABSTRACT FROM AUTHOR]

Neutrinos are believed to be the most abundant fermions in the Universe, but their masses are unknown, except for being non-zero but much smaller than other fermions. Cosmological relic neutrinos could also have non-zero chemical potentials (or asymmetries). Using neutrino-involved N -body simulations, we investigate the neutrino effects on the matter pairwise velocity, which itself is an interesting probe of cosmology. We find that for light-halo ([1011, 1013] M⊙) mean pairwise velocity, in the transition range ([4, 15] Mpc), the effects of neutrino masses overwhelm the effects of neutrino asymmetries, while in the two-halo-group range ([25, 50] Mpc), for both light and heavy haloes ([1013, 1015] M⊙), the effects of neutrino asymmetries dominate, making it possible to disentangle the two effects. We provide fitting formulae to quantify the effects of neutrino mass and asymmetry on halo–halo pairwise velocities. [ABSTRACT FROM AUTHOR]

We study a neutrino mass model with A 4 discrete flavor symmetry using a type-I seesaw mechanism. The inclusion of extra flavons in our model leads to deviations from the exact tribimaximal mixing pattern resulting in a nonzero θ 1 3 consistent with the recent experimental results and a sum rule for light neutrino masses is also obtained. In this framework, a connection is established among the neutrino mixing angles-reactor mixing angle ( θ 1 3 ), solar mixing angle ( θ 1 2 ), and atmospheric mixing angle ( θ 2 3 ). This model also allows us a prediction of Dirac CP-phase and Jarlskog parameter (J). The octant of the atmospheric mixing angle θ 2 3 occupies the lower octant. Our model prefers Normal Hierarchy (NH) than Inverted Hierarchy (IH). We use the parameter space of our model of neutrino masses to study the neutrinoless double beta decay parameter m β β . [ABSTRACT FROM AUTHOR]

Axions and dark photons are common in many extensions of the Standard Model. The dark axion portal — an axion coupling to the dark photon and photon — can significantly modify their phenomenology. We study the cosmological constraints on the dark axion portal from Cosmic Microwave Background (CMB) bounds on the energy density of dark radiation, ∆Neff. By computing the axion-photon-dark photon collision terms and solving the Boltzmann equations including their effects, we find that light axions are generally more constrained by ∆Neff than from supernova cooling or collider experiments. However, with dark photons at the MeV scale, a window of parameter space is opened up above the supernova limits and below the experimental exclusion, allowing for axion decay constants as low as fa ~ 104 GeV. This region also modifies indirectly the neutrino energy density, thus relaxing the cosmological upper bound on the sum of neutrino masses. Future CMB measurements could detect a signal or close this open window on the dark axion portal. [ABSTRACT FROM AUTHOR]

Left Right Symmetric Model (LRSM) being an extension of the Standard model of particle physics incorporates within itself Type-I and Type-II seesaw mass terms naturally. Both the mass terms can have significant amount of contribution to the resulting light neutrino mass within the model and hence on the different phenomenology associated within. In this paper, we have thoroughly analyzed and discussed the implications of specifying different weightages to both the mass terms and also the study has been carried out for different values of which is mass of the right-handed gauge boson. This paper also gives a deeper insight into the new physics contributions of Neutrinoless Double Beta Decay (0νββ) and their variations with the net baryon asymmetry arising out of the model. Therefore, the main objective of the present paper rests on investigating the implications of imposing different weightage to the type-I and type-II seesaw terms and different values of on the new physics contributions of 0νββ and net baryon asymmetry arising out as a result of resonant leptogenesis. LRSM in this work has been realized using modular group of level 3, Γ(3) which is isomorphic to non-abelian discrete symmetry group A4, the advantage being the non-requirement of flavons within the model and hence maintaining the minimality of the model. [ABSTRACT FROM AUTHOR]

A convincing explanation of the smallness of neutrino masses is represented by the Type-I Seesaw mechanism, where the two measured neutrino mass differences can be generated by introducing at least two right-handed neutrinos. In an ultraviolet complete model, it is possible to dynamically generate the heavy Majorana scale through the spontaneous symmetry breaking of a global Abelian symmetry and the most economical realisation consists in coupling the two exotic neutral leptons to a singlet complex scalar field. The associated Goldstone boson is often dubbed as Majoron, which may achieve a non-vanishing mass by means of a small term that explicitly breaks the Abelian symmetry. In a generic model, the neutrino and Majoron mass generation mechanisms are completely uncorrelated. In this paper, instead, we reduce the landscape of possible models proposing a unique, minimal and predictive framework in which these two types of masses are strictly tied and arise from the same source. Bounds from various terrestrial and astrophysical experiments are discussed. [ABSTRACT FROM AUTHOR]

In this paper we investigate how well the nature of heavy neutral leptons can be determined at a future lepton collider, after its potential discovery. Considered in a simplified model are prompt decays of the neutrino in the mass range from 100 GeV to 10 TeV. We study event selection and application of multivariate analyses to determine whether such a newly discovered particle is of the Dirac or Majorana nature. Combining lepton charge and kinematic event variables, we find that the nature of a heavy neutrino, whether it is a Dirac or a Majorana particle, can be determined at 95% C.L. almost in the whole discovery range. We will briefly speculate about other than the studied channels and the robustness of this statement in more general models of heavy neutral leptons, particularly on the complementarity of high-energy electron-positron vs. muon colliders on resolving the flavor structure of heavy neutrinos. [ABSTRACT FROM AUTHOR]

The strong CP problem is solved in Parity symmetric theories, with the electroweak gauge group containing SU(2)L × SU(2)R broken by the minimal set of Higgs fields. Neutrino masses may be explained by adding the same number of gauge singlet fermions as the number of generations. The neutrino masses vanish at tree-level and are only radiatively generated, leading to larger couplings of right-handed neutrinos to Standard Model particles than with the tree-level seesaw mechanism. We compute these radiative corrections and the mixing angles between left- and right-handed neutrinos. We discuss sensitivities to these right-handed neutrinos from a variety of future experiments that search for heavy neutral leptons with masses from tens of MeV to the multi-TeV scale. [ABSTRACT FROM AUTHOR]

We explore the connection between low-scale CP-violating Dirac phase (δ) and high-scale leptogenesis in a Left-Right Symmetric Model (LRSM) with scalar bidoublet and doublets. The fermion sector of the model is extended with one sterile neutrino (SL) per generation to implement a double seesaw mechanism in the neutral fermion mass matrix. The double seesaw is performed via the implementation of type-I seesaw twice. The first seesaw facilitates the generation of Majorana mass term for heavy right-handed (RH) neutrinos (NR), and the light neutrino mass becomes linearly dependent on SL mass in the second. In our framework, we have taken charge conjugation (C) as the discrete left-right (LR) symmetry. This choice assists in deriving the Dirac neutrino mass matrix (MD) in terms of the light and heavy RH neutrino masses and light neutrino mixing matrix UPMNS (containing δ). We illustrate the viability of unflavored thermal leptogenesis via the decay of RH neutrinos by using the obtained MD with the masses of RH neutrinos as input parameters. A complete analysis of the Boltzmann equations describing the asymmetry evolution is performed in the unflavored regime, and it is shown that with or without Majorana phases, the CP-violating Dirac phase is sufficient to produce the required asymmetry in the leptonic sector within this framework for a given choice of input parameters. Finally, we comment on the possibility of constraining our model with the current and near-future oscillation experiments, which are aimed at refining the value of δ. [ABSTRACT FROM AUTHOR]

We propose a novel scenario to explain the matter-antimatter asymmetry by twofold leptogenesis, wherein heavy Majorana neutrinos exhibit temperature-dependent masses and engage in CP-violating decays. This scenario envisages two distinct phases of leptogenesis: one occurring above the electroweak scale and the other below it. The sphaleron process converts the first lepton asymmetry to baryon asymmetry, but not the second one due to its decoupling. This mechanism potentially explains the significant discrepancy between baryon and lepton asymmetries, as suggested by recent observations of Helium-4. Furthermore, our model implies that the present masses of Majorana neutrinos are lighter than the electroweak scale, offering a tangible avenue for experimental verification in various terrestrial settings. [ABSTRACT FROM AUTHOR]

The Standard Model of electroweak interactions is based on the fundamental SU(2)weak × U(1)elect representation. It assumes massless neutrinos and purely left-handed massive W ± and Z0 bosons to which one should add the massless photon. The existence, verified experimentally, of neutrino oscillations poses a challenge to this scheme, since the oscillations take place between at least three massive neutrinos belonging to a mass hierarchy still to be determined. One should also take into account the possible existence of sterile neutrino species. In a somehow different context, the fundamental nature of the strong interaction component of the forces in nature is described by the, until now, extremely successful representation based on the SU(3)strong group which, together with the confining rule, give a description of massive hadrons in terms of quarks and gluons. To this is added the minimal U(1) Higgs group to give mass to the otherwise massless generators. This representation may also be challenged by the existence of both dark matter and dark energy, of still unknown composition. In this note, we shall discuss a possible connection between these questions, namely the need to extend the SU(3)strong × SU(2)weak × U(1)elect to account for massive neutrinos and dark matter. The main point of it is related to the role of axions, as postulated by Roberto Peccei and Helen Quinn. The existence of neutral pseudo-scalar bosons, that is, the axions, has been proposed long ago by Peccei and Quinn to explain the suppression of the electric dipole moment of the neutron. The associated U(1)PQ symmetry breaks at very high energy, and it guarantees that the interaction of other particles with axions is very weak. We shall review the axion properties in connection with the apparently different contexts of neutrino and dark matter physics. [ABSTRACT FROM AUTHOR]

In this paper, we discuss a minimal lepton flavor model with two modular A 4 symmetries, one acting on neutrinos and the other acting on charged leptons. Two corresponding moduli fields are restricted at stabilizers. To avoid vanishing or degenerate lepton masses, the stabilizer in the charged lepton sector always preserves a Z 3 symmetry, and that in the neutrino preserves a Z 2 symmetry. By scanning all viable stabilizers, a unique Trimaximal TM2 mixing is predicted. However, the prediction of the lightest neutrino mass and the mass parameter in neutrinoless double beta decay, as well as two Majorana phases, are different and classified into three cases. [ABSTRACT FROM AUTHOR]

We consider a minimal renormalizable non-supersymmetric E 6 Grand Unified Theory using fundamental representation 27 for fermions and scalars. The scalar with adjoint representation 78 is also taken for direct breaking of E 6 to SM. The proposed model, guided by TeV-scale vector-like fermions and scalar leptoquark, offers successful gauge unification even in the absence of any intermediate symmetry. Embedded with threshold corrections, it is shown to be compatible with the present experimental limit on proton decay lifetime. The unique feature of the model shows that the GUT threshold corrections to the unification mass is controlled by superheavy gauge bosons only, thereby minimizing the uncertainty of the GUT predictions. The scalar leptoquark and vector-like fermions residing in 27 representation can explain flavor physics anomalies like R D (∗) as reported by the LHCb collaboration and the muon anomalous magnetic moment reported by the recent muon g − 2 experiment at Fermilab. The model can also predict a sub-eV scale neutrino at one-loop level via exchange of W and Z gauge bosons through MRIS mechanism. [ABSTRACT FROM AUTHOR]

The discovery of the Higgs particle has completed the Standard Model of elementary interactions which is stunningly successful in describing most of the elementary processes observed so far in the laboratories. Nevertheless, it is not the Theory of Everything. Its structure faces some theoretical puzzles and, even more importantly, it leaves unexplained neutrino masses and several fundamental astrophysical observations. Thus, the quest for a deeper theory is at present the main experimental and theoretical challenge in particle physics. However, contrary to the past research characterized by certain continuity and clear goals, we are now in a turning point surfing into totally unknown territory beyond the Standard Model physics. Precision measurements of the Higgs particle properties is one of the promising directions in the search for extensions to the existing theory. This article is part of the theme issue 'The particle-gravity frontier'. [ABSTRACT FROM AUTHOR]

Nonlinear gravitational evolution induces strong nonlinearities in the observed cosmological density fields, leading to positive off-diagonal correlations in the power spectrum covariance. This has caused the information saturation in the power spectrum, e.g., the neutrino mass constraints from the nonlinear power spectra are lower than their linear counterparts by a factor of ∼2 at z = 0. In this paper, we explore how nonlinear reconstruction methods improve the cosmological information from nonlinear cosmic fields. By applying nonlinear reconstruction to cold dark matter fields from the Quijote simulations, we find that nonlinear reconstruction can improve the constraints on cosmological parameters significantly, nearly reaching the linear theory limit. For neutrino mass, the result is only 12% lower than the linear power spectrum, i.e., the theoretical best result. This makes nonlinear reconstruction an efficient and useful method to extract neutrino information from current and upcoming galaxy surveys. [ABSTRACT FROM AUTHOR]

The next-generation water Cherenkov Hyper-Kamiokande detector will be able to detect thousands of neutrino events from a galactic Supernova explosion via Inverse Beta Decay processes followed by neutron capture on Gadolinium. This superb statistics provides a unique window to set bounds on neutrino properties, as its mass and lifetime. We shall explore the capabilities of such a future detector, constraining the former two properties via the time delay and the flux suppression induced in the Supernovae neutrino time and energy spectra. Special attention will be devoted to the statistically sub-dominant elastic scattering induced events, normally neglected, which can substantially improve the neutrino mass bound via time delays. When allowing for a invisible decaying scenario, the 95% CL lower bound on τ / m is almost one order of magnitude better than the one found with SN1987A neutrino events. Simultaneous limits can be set on both m ν and τ ν , combining the neutrino flux suppression with the time-delay signature: the best constrained lifetime is that of ν 1 , which has the richest electronic component. We find τ ν 1 ≳ 4 × 10 5 s at 95% CL. The tightest 95% CL bound on the neutrino mass we find is 0.34 eV, which is not only competitive with the tightest neutrino mass limits nowadays, but also comparable to future laboratory direct mass searches. Both mass and lifetime limits are independent on the mass ordering, which makes our results very robust and relevant. [ABSTRACT FROM AUTHOR]

We study the prospects of probing neutrino mass models at the newly proposed antimuon collider μ TRISTAN, involving μ + e - scattering at s = 346 GeV and μ + μ + scattering at s = 2 TeV. We show that μ TRISTAN is uniquely sensitive to leptophilic neutral and doubly-charged scalars naturally occurring in various neutrino mass models, such as Zee, Zee–Babu, cocktail, and type-II seesaw models, over a wide range of mass and coupling values, well beyond the current experimental constraints. It also allows for the possibility to correlate the collider signals with neutrino mixing parameters and charged lepton flavor violating observables. [ABSTRACT FROM AUTHOR]

We study the possibility of probing the radiative Dirac seesaw model with dark sector particles going inside the loop, popularly referred to as the Dirac scotogenic model via measurements of effective relativistic degrees of freedom Δ N eff at cosmic microwave background (CMB) experiments. The loop suppression and additional free parameters involved in neutrino mass generation allow large (∼ O (1)) coupling of light Dirac neutrinos with the dark sector particles. Such large Yukawa coupling not only dictates the relic abundance of heavy fermion singlet dark matter but also can lead to the thermalisation of the right chiral part of Dirac neutrinos, generating additional relativistic degrees of freedom Δ N eff. We find that the parameter space consistent with dark matter phenomenology and neutrino mass bounds can also be probed at future cosmic microwave background experiments like CMB-S4 via precision measurements of Δ N eff. The same parameter space, while leading to loop-suppressed direct detection cross-section of dark matter outside future sensitivities, can also have other interesting and complementary observational prospects via charged lepton flavour violation and collider signatures. [ABSTRACT FROM AUTHOR]

In this paper, we have estimated the neutrino mass ordering and the CP violation sensitivity of the proposed Protvino to ORCA (P2O) experiment after 6 years of data-taking. Both unitary and non-unitary 3 × 3 neutrino mass mixing have been considered in the simulations. A forecast analysis deriving possible future constraints on non-unitary parameters at P2O have been performed. [ABSTRACT FROM AUTHOR]

We study lepton flavour universality violation in SM boson decays in low-scale seesaw models of neutrino mass generation, also addressing other electroweak precision observables. We compute the electroweak next-to-leading order corrections, which turn out to be important – notably in the case of the invisible decay width of the Z boson, for which the corrections can be as large as the current experimental uncertainty. As a well-motivated illustrative study case, we choose a realisation of the Inverse Seesaw mechanism, and discuss the complementary role of lepton flavour conserving, lepton flavour violating and precision observables, both in constraining and in probing such models of neutrino mass generation. Our findings suggest that invisible Z decays are especially important, potentially at the origin of the most stringent constraints for certain regimes of the Inverse Seesaw (while complying with charge lepton flavour violation and other electroweak precision tests). We also discuss the probing power of the considered observables in view of the expected improvement in experimental precision at FCC-ee. [ABSTRACT FROM AUTHOR]

In the PMNS matrix, the relation | U μ i |   =   | U τ i | (with i = 1 , 2 , 3 ) is experimentally favored at the present stage. The possible implications of this relation on some hidden flavor symmetry has attracted a lot of interest in the neutrino community. In this paper, we analyze the implications of | U μ i |   =   | U τ i | (with i = 1 , 2 , 3 ) in the context of the canonical seesaw mechanism. We also show that the minimal μ − τ symmetry proposed in JHEP 06 (2022) 034 is a possible but not necessary reason for the above-mentioned relation. [ABSTRACT FROM AUTHOR]

We endeavour to constrain the neutrino mass matrix on the phenomenological ground and procure model-independent textures by emphasizing on the simple linear relationships among the mass matrix elements. These simple textures predict the two Majorana phases. In this regard, two types of parametrization of neutrino mass matrix: general and exponential are employed. We obtain fifty-three predictive neutrino mass matrix textures, out of which twenty-eight are associated with the general parametrization, and the rest belong to the exponential one. Apart from Type-A/P textures, the rest deal with the prediction of a few other oscillation parameters as well. We try to realize the proposed textures in the light of A 4, Δ(27) and T 7 symmetry groups. [ABSTRACT FROM AUTHOR]

Assuming that the sbottom is the lightest supersymmetric particle (LSP), we carry out an analysis of the relevant signals expected at the LHC. The discussion is established in the framework of the μ ν SSM, where the presence of R-parity violating couplings involving right-handed neutrinos solves simultaneously the μ -problem and the accommodation of neutrino masses and mixing angles. The sbottoms are pair produced at the LHC, decaying to a lepton and a top quark or a neutrino and a bottom quark. The decays can be prompt or displaced, depending on the regions of the parameter space of the model. We focus the analysis on the right sbottom LSP, since the left sbottom is typically heavier than the left stop because of the D-term contribution. We compare the predictions of this scenario with ATLAS and CMS searches for prompt and long-lived particles. To analyze the parameter space we sample the μ ν SSM for a right sbottom LSP, paying special attention to reproduce the current experimental data on neutrino and Higgs physics, as well as flavor observables. For displaced (prompt) decays, our results translate into lower limits on the mass of the right sbottom LSP of about 1041 GeV (1070 GeV). The largest possible value found for the decay length is about 3.5 mm. [ABSTRACT FROM AUTHOR]

This article is a tribute to Harald Fritzsch, a physicist who had a strong interest in topics such as strong interactions, the origin of neutrino mass, and the parameters of the standard model. The author shares personal experiences of their time spent with Fritzsch, including a visit to the Arizona-Sonora desert museum. The article also mentions a physics colloquium Fritzsch gave at the University of Arizona and a presentation he made in Rio de Janeiro on the time dependence of QCD. The author expresses their sadness at Fritzsch's passing and acknowledges his contributions as a friend and colleague. [Extracted from the article]

Scalar leptoquarks naturally arise within unified theories, offering a promising avenue for addressing one of the most significant challenges of the Standard Model–the existence of non-zero neutrino masses. In this work, we present a unified theory based on the SU(5) gauge group, where neutrino mass appears at the two-loop level via the propagation of scalar leptoquarks. Due to the unified framework, the charged fermion and neutrino masses and mixings are entangled and determined by a common set of Yukawa couplings. These exotic particles not only shed light on the neutrino mass generation mechanism but also help to achieve the unification of gauge couplings and are expected to lead to substantial lepton flavor violating rates, offering tangible opportunities for experimental verification. Reproducing the observed neutrino mass scale necessitates that a set of leptoquarks reside a few orders of magnitude below the unification scale–a specific feature of the proposed scenario. Moreover, maximizing the unification scale implies TeV scale new physics states, making them accessible at colliders. The diverse roles that leptoquarks play highlight the elegance and predictive ability of the proposed unified model. [ABSTRACT FROM AUTHOR]

We derive verifiable two-zero textures in the framework of a three-loop induced neutrino mass model applying a modular A 4 symmetry for the lepton sector. Interestingly, the neutrino mass structure is determined by assignments of the right-handed charged-lepton particles only. We show all the possible texture patterns and demonstrate their analytical and numerical analyses. Finally, we mention a possibility of detection for doubly-charged boson via colliders that decays into specific modes due to the flavor symmetry. [ABSTRACT FROM AUTHOR]

We consider a general, anomaly free U (1) ′ extension of the Standard Model (SM) where the neutrino mass is generated at the tree level via the inverse seesaw mechanism. The model contains three right handed neutrinos, three additional singlet fermions, one extra complex scalar and a neutral gauge boson (Z ′). Instead of resorting to a specific U (1) extension, we consider a class of models by taking the U (1) ′ charges of the scalars to be free parameters. Here, we assign one pair of the pseudo-Dirac degenerate sterile neutrinos as Dark Matter (DM) candidates which are produced by the freeze-in mechanism. Considering different mass regimes of the DM, Z ′ and reheating temperature, we obtain constraints on the U (1) ′ charges giving the correct relic abundance. We have also obtained constraints on Z ′ mass and coupling from consideration of relic density as well as high energy collider experiments like ATLAS in case of heavy Z ′ or in intensity and lifetime frontier experiments like DUNE, FASERs, and ILC beam dump which are looking for light Z ′. Additionally, in this model, the decay of pseudo-Dirac DM into active neutrinos can explain the 511 keV line observed by the INTEGRAL satellite. [ABSTRACT FROM AUTHOR]

Small neutrino masses confirmed in the neutrino oscillation experiments indicate the need for new physics beyond the standard model. Seesaw mechanism is an interesting way to extend the standard model for explaining the neutrino masses. In a low-scale type-I seesaw mechanism, the tiny masses of neutrinos can be explained by heavy Majorana neutrino masses. Heavy Majorana neutrinos can lead to lepton-number-violating processes and the induced CP violation can contribute to the baryon asymmetry in the Universe. Heavy Majorana neutrinos can also lead to lepton-number-conserving processes and in this paper, we study the CP violation in lepton-number-conserving processes through heavy Majorana neutrinos at future lepton colliders. New possible observations of CP violation can also be connected to evidences of new physics beyond the standard model. [ABSTRACT FROM AUTHOR]

This paper's novelty lies in introducing a hybrid scoto-seesaw model rooted in A 4 discrete modular symmetry leading to several interesting phenomenological implications. The scoto-seesaw framework leads to generation of one mass square difference (Δ m atm 2) using the type-I seesaw mechanism at the tree level. Additionally, the scotogenic contribution is vital in obtaining the other mass square difference (Δ m sol 2) at the loop level, thus providing a clear interpretation of the two different mass square differences. The non-trivial transformation of Yukawa couplings under the A 4 modular symmetry helps to explore neutrino phenomenology with a specific flavor structure of the mass matrix. In addition to predictions for neutrino mass ordering, mixing angles and CP phases, this setup leads to precise predictions for ∑ m i as well as | m e e |. In particular, the model predicts ∑ m i ∈ (0.073 , 0.097) eV and | m e e | ∈ (3.15 , 6.66) × 10 − 3 eV range; within reach of upcoming experiments. Furthermore, our model is also promising for addressing lepton flavor violations, i.e., ℓ α → ℓ β γ , ℓ α → 3 ℓ β and μ − e conversion rates while staying within the realm of current experimental limits. [ABSTRACT FROM AUTHOR]

The Jiangmen Underground Neutrino Observatory (JUNO), a 20 kton multi-purpose low background Liquid Scintillator (LS) detector, was proposed primarily to determine the neutrino mass ordering. To suppress the radioactivity from the surrounding rocks and tag cosmic muons, the JUNO central detector is submerged in a Water Cherenkov Detector (WCD). In addition to being used in the WCD, ultrapure water is used in LS filling, for which the 226Ra concentration in water needs to be less than 50 μ Bq/m 3. To precisely measure the 226Ra concentration in water, a 6.0 μ Bq/m 3 226Ra concentration in water measurement system has been developed. In this paper, the detail of the measurement system as well as the 226Ra concentration measurement result in regular EWII ultrapure water will be presented. [ABSTRACT FROM AUTHOR]

We propose a scenario where a high scale seesaw origin of light neutrino mass and gravitational dark matter (DM) in MeV-TeV ballpark originating from primordial black hole (PBH) evaporation can be simultaneously probed by future observations of stochastic gravitational wave (GW) background with multiple tilts or spectral breaks. A high scale breaking of an Abelian gauge symmetry ensures the dynamical origin of the seesaw scale while also leading to the formation of cosmic strings responsible for generating stochastic GW background. The requirement of a correct DM relic in this ballpark necessitates the inclusion of a diluter as PBH typically leads to DM overproduction. This leads to a second early matter dominated epoch after PBH evaporation due to the long-lived diluter. These two early matter dominated epochs, crucially connected to the DM relic, lead to multiple spectral breaks in the otherwise scale-invariant GW spectrum formed by cosmic strings. We find interesting correlations between DM mass and turning point frequencies of GW spectrum which are within reach of several near future experiments like LISA, BBO, ET, CE, etc. [ABSTRACT FROM AUTHOR]