Search

The Jiangmen Underground Neutrino Observatory (JUNO) experiment is the next-generation neutrino experiment that aims at exploring the neutrino mass hierarchy problem. Located 700 m underground in Jiangmen, China, JUNO's central detector is an acrylic sphere filled with 20 kt of liquid scintillator with linear alkylbenzene (LAB) as solvent. To achieve the unprecedented energy resolution of σ E / E ⩽ 3 % , the LAB used in JUNO is required for excellent transparency at the wavelength around 430 nm. In cooperation with Jinling Petrochemical (Nanjing), the newly developed LAB shows an improved attenuation length. The resulting transparency of the LAB requires higher sensitivity in measurement. We have, therefore, upgraded the apparatus and the analysis method for higher precision. In this article, we present the upgraded apparatus and the analysis on improving the measurement error. Among the many new samples, the type NJ66 yields an attenuation length of approximately 30 m. The analysis has applied statistical methods with Monte Carlo simulations. A new model is proposed to account for the deviations between data and the Beer–Lambert model. The long attenuation length of LAB observed in this study suggests feasibility to reach the goal on energy resolution required by JUNO. [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 Z2⊗Z2′, 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 r0.05≈1.68×10−6, the inflaton mass MΦ≈5.05×1010GeV, the reheating temperature Tre≈8.29×1010GeV, the CDM mass MS≈256GeV, ηB≈6.14×10−10 and h≈0.73, 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]

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]

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]

Sterile neutrinos in the keV mass range present a viable candidate for dark matter. They can be detected through single β -decay, where they cause small spectral distortions. The Karlsruhe Tritium Neutrino (KATRIN) experiment aims to search for keV-scale sterile neutrinos with high sensitivity. To achieve this, the KATRIN beamline will be equipped with a novel multi-pixel silicon drift detector focal plane array named TRISTAN. In this study, we present the performance of a TRISTAN detector module, a component of the eventual 9-module system. Our investigation encompasses spectroscopic aspects such as noise performance, energy resolution, linearity, and stability. [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]

The recent high precision measurement of W boson mass by CDF-II collaboration points to the contribution(s) of new physics beyond the Standard Model (SM). One of the minimalistic ways to account for the anomalous W boson mass is by introducing a hyperchargeless real SU (2) L triplet scalar whose vacuum expectation value (VEV) explicitly contributes to the W boson mass at the tree level while the Z boson mass remains the same. Such a triplet can be naturally embedded in a singlet-triplet scotogenic model for one-loop neutrino mass generated by dark sector particles running in the loop. We discuss the detailed phenomenology of the model, obtaining the parameter space consistent with the CDF-II W boson mass measurements. The dark matter as well as the constraints comings from S , T , U parameters are also analyzed. [ABSTRACT FROM AUTHOR]

A number of recent studies have found evidence for a tension between observations of large-scale structure (LSS) and the predictions of the standard model of cosmology with the cosmological parameters fit to the cosmic microwave background (CMB). The origin of this ' S 8 tension' remains unclear, but possibilities include new physics beyond the standard model, unaccounted for systematic errors in the observational measurements and/or uncertainties in the role that baryons play. Here, we carefully examine the latter possibility using the new FLAMINGO suite of large-volume cosmological hydrodynamical simulations. We project the simulations onto observable harmonic space and compare with observational measurements of the power and cross-power spectra of cosmic shear, CMB lensing, and the thermal Sunyaev-Zel'dovich (tSZ) effect. We explore the dependence of the predictions on box size and resolution and cosmological parameters, including the neutrino mass, and the efficiency and nature of baryonic 'feedback'. Despite the wide range of astrophysical behaviours simulated, we find that baryonic effects are not sufficiently large to remove the S 8 tension. Consistent with recent studies, we find the CMB lensing power spectrum is in excellent agreement with the standard model, while the cosmic shear power spectrum, tSZ effect power spectrum, and the cross-spectra between shear, CMB lensing, and the tSZ effect are all in varying degrees of tension with the CMB-specified standard model. These results suggest that some mechanism is required to slow the growth of fluctuations at late times and/or on non-linear scales, but that it is unlikely that baryon physics is driving this modification. [ABSTRACT FROM AUTHOR]

We introduce the Virgo Consortium's FLAMINGO suite of hydrodynamical simulations for cosmology and galaxy cluster physics. To ensure the simulations are sufficiently realistic for studies of large-scale structure, the subgrid prescriptions for stellar and AGN feedback are calibrated to the observed low-redshift galaxy stellar mass function and cluster gas fractions. The calibration is performed using machine learning, separately for each of FLAMINGO's three resolutions. This approach enables specification of the model by the observables to which they are calibrated. The calibration accounts for a number of potential observational biases and for random errors in the observed stellar masses. The two most demanding simulations have box sizes of 1.0 and 2.8 Gpc on a side and baryonic particle masses of 1 × 108 and |$1\times 10^9\, \text{M}_\odot$|⁠ , respectively. For the latter resolution, the suite includes 12 model variations in a 1 Gpc box. There are 8 variations at fixed cosmology, including shifts in the stellar mass function and/or the cluster gas fractions to which we calibrate, and two alternative implementations of AGN feedback (thermal or jets). The remaining 4 variations use the unmodified calibration data but different cosmologies, including different neutrino masses. The 2.8 Gpc simulation follows 3 × 1011 particles, making it the largest ever hydrodynamical simulation run to z  = 0. Light-cone output is produced on-the-fly for up to 8 different observers. We investigate numerical convergence, show that the simulations reproduce the calibration data, and compare with a number of galaxy, cluster, and large-scale structure observations, finding very good agreement with the data for converged predictions. Finally, by comparing hydrodynamical and 'dark-matter-only' simulations, we confirm that baryonic effects can suppress the halo mass function and the matter power spectrum by up to ≈20 per cent. [ABSTRACT FROM AUTHOR]

The CMS experiment at the CERN LHC is designed to study elementary particles, within the framework of the Standard Model as well as beyond. The discovery of the Higgs boson of mass of 125 GeV by the CMS and ATLAS Collaborations in 2012 marks a stellar success of the LHC physics program. Despite its huge success, the SM is known to be inadequate to explain stability of Higgs mass, dark matter, matter–antimatter asymmetry, and masses of the neutrinos, to name a few. Since the beginning of the LHC operations more than a decade ago, the CMS Collaboration has reported many measurements of the SM processes and searches for new physics in proton–proton collisions at s = 7, 8 and 13 TeV. It also studies collisions of heavy ions. The large and complex experiment requires intense collaboration of a large team of dedicated researchers to infer physics from the data collected. Indian participants in the CMS experiment have made significant contributions to several key areas of detector development, experimental operations, and physics analysis programs. Given the collaborative nature of these efforts, it is not possible to isolate the contributions of individual countries or researchers. It is also not possible to discuss all the physics results published by the collaboration. In this article contributed to the special issue about India and the CERN, we present an overview of the physics program of the CMS Collaboration and discuss a few key results picked by the authors with slight preference given to those with significant contributions from Indian physicists. [ABSTRACT FROM AUTHOR]

We identify the QCD axion and right-handed (sterile) neutrinos as bound states of an SU(5) chiral gauge theory with Peccei-Quinn (PQ) symmetry arising as a global symmetry of the strong dynamics. The strong dynamics is assumed to spontaneously break the PQ symmetry, producing a high-quality axion and naturally generating Majorana masses for the right-handed neutrinos at the PQ scale. The composite sterile neutrinos can directly couple to the left-handed (active) neutrinos, realizing a standard see-saw mechanism. Alternatively, the sterile neutrinos can couple to the active neutrinos via a naturally small mass mixing with additional elementary states, leading to light sterile neutrino eigenstates. The SU(5) strong dynamics therefore provides a common origin for a high-quality QCD axion and sterile neutrinos. [ABSTRACT FROM AUTHOR]

We consider the possibility that neutrino masses arise from the exchange of dark matter states. We examine in detail the phenomenology of fermionic dark matter in the singlet-triplet scotogenic model. We explore the case of singlet-like fermionic dark matter, taking into account all coannihilation effects relevant for determining its relic abundance, such as fermion-fermion and scalar-fermion coannihilation. Although this in principle allows for dark matter below 60 GeV, the latter is in conflict with charged lepton flavour violation (cLFV) and/or collider physics constraints. We examine the prospects for direct dark matter detection in upcoming experiments up to 10 TeV. Fermion-scalar coannihilation is needed to obtain viable fermionic dark matter in the 60-100 GeV mass range. Fermion-fermion and fermion-scalar coannihilation play complementary roles in different parameter regions above 100 GeV. [ABSTRACT FROM AUTHOR]

We consider a scale-invariant inverse seesaw model with dynamical breaking of gauge symmetry and lepton number. In some regions of the parameter space, the Majoron — the pseudo-Goldstone of lepton number breaking — is a viable dark matter candidate. The bound on the Majoron decay rate implies a very large dilaton vacuum expectation value, which also results in a suppression of other dark matter couplings. Because of that, the observed dark matter relic abundance can only be matched via the freeze-in mechanism. The scalar field which gives mass to heavy neutrinos can play the role of the inflaton, resulting in a tensor-to-scalar ratio r ≲ 0.01 for metric inflation and r ≲ 0.21 for Palatini gravity. [ABSTRACT FROM AUTHOR]

We explore the complementarity of direct detection (DD) and spallation source (SS) experiments for the study of sterile neutrino physics. We focus on the sterile baryonic neutrino model: an extension of the Standard Model that introduces a massive sterile neutrino with couplings to the quark sector via a new gauge boson. In this scenario, the inelastic scattering of an active neutrino with the target material in both DD and SS experiments gives rise to a characteristic nuclear recoil energy spectrum that can allow for the reconstruction of the neutrino mass in the event of a positive detection. We first derive new bounds on this model based on the data from the COHERENT collaboration on CsI and LAr targets, which we find do not yet probe new areas of the parameter space. We then assess how well future SS experiments will be able to measure the sterile neutrino mass and mixings, showing that masses in the range ~15 − 50 MeV can be reconstructed. We show that there is a degeneracy in the measurement of the sterile neutrino mixing that substantially affects the reconstruction of parameters for masses of the order of 40 MeV. Thanks to their lower energy threshold and sensitivity to the solar tau neutrino flux, DD experiments allow us to partially lift the degeneracy in the sterile neutrino mixings and considerably improve its mass reconstruction down to 9 MeV. Our results demonstrate the excellent complementarity between DD and SS experiments in measuring the sterile neutrino mass and highlight the power of DD experiments in searching for new physics in the neutrino sector. [ABSTRACT FROM AUTHOR]

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