Neutrino Mixing Matrix Research Articles

On the orthogonal matrix in the Casas-Ibarra parametrization for the Yukawa interactions of Majorana neutrinos

The Casas-Ibarra (CI) parametrization of the Yukawa coupling matrix of Majorana neutrinos is generalized by considering the exact seesaw relation and including non-unitarity of the 3×3 Pontecorvo-Maki-Nakagawa-Sakata (PMNS) flavor mixing matrix. With the help of a full 6×6 Euler-like block description of the flavor structure for the seesaw mechanism, we find that the orthogonal matrix O in the CI parametrization can be expressed as Oij=Mj/miFij with mi and Mj being the masses of light and heavy Majorana neutrinos and Fij consisting of the PMNS and active-sterile flavor mixing parameters (for i,j=1,2,3). Assuming a specific pattern of O is therefore equivalent to imposing some special conditions on the seesaw parameter space.

On Quark–Lepton Mixing and the Leptonic CP Violation

In the absence of a Grand Unified Theory framework, connecting the values of the mixing parameters in the quark-and-lepton sector is a difficult task, unless one introduces ad hoc relations among the matrices that diagonalize such different kinds of fermions. In this paper, we discuss in detail the possibility that the PMNS matrix is given by the product UPMNS=VCKM★T★, where T comes from the diagonalization of a see-saw like mass matrix that can be of a Bimaximal (BM), Tri-Bimaximal (TBM) and Golden Ratio (GR) form, and identify the leading corrections to such patterns that allow for a good fit to the leptonic mixing matrix as well as to the CP phase. We also show that the modified versions of BM, TBM and GR can easily accommodate the solar and atmospheric mass differences.

Calculable neutrino Dirac mass matrix and one-loop θ¯ in the minimal left-right symmetric model

We revisit the contribution to the strong CP parameter θ¯ from leptonic CP violation at one-loop level in the minimal left-right symmetric model in the case of generalized parity as the left-right symmetry. The Hermitian neutrino Dirac mass matrix MD can be calculated using the light and heavy neutrino masses and mixings. We propose a parametrization of the right-handed neutrino mixing matrix VR and construct the heavy neutrino mass that maintains the Hermiticity of MD. We further apply it to evaluate the one-loop θ¯, denoted as θ¯loop, as a function of the sterile neutrino masses for explicit examples of VR. By requiring the magnitude of θ¯loop≲10−10, we derive the upper limits on the sterile neutrino masses, which are within reach of direct searches at the Large Hadron Collider and neutrinoless double beta decay experiments. Furthermore, our parametrization is pertinent for other phenomenological investigations. Published by the American Physical Society 2024

Imaging systems for the liquid Argon target of SAND at the DUNE Near Detector Complex

The Deep Underground Neutrino Experiment (DUNE) has among its primary goals the determination of the neutrino mass ordering and the possible CP-violating phase in the neutrino mixing matrix. The System for On-Axis Neutrino Detection (SAND) is one of the three components of the DUNE Near Detector complex, permanently located on-axis to monitor the neutrino beam stability and measure its flux. SAND includes a novel liquid Argon detector - GRAIN - designed to image neutrino interactions using scintillation light produced in Ar by charged particles, eliminating the dependence on slow charge collection of LAr TPCs. Two optical systems are currently being developed for GRAIN, both based on Silicon Photomultiplier (SiPM) matrices, coupled either to UV cryogenic lenses or Coded Aperture masks. This contribution will present the design of GRAIN optical systems and their spatial resolution performance in preliminary simulation studies.

SU(2)L deconstruction and flavour (non)-universality

We study two-site deconstructions of the SU(2)L gauge group factor of the SM. Models based on this approach can explain the hierarchies of the quark masses and CKM mixing between third and light families if these fields are localised on different sites by the presence of hierarchical new physics scales. The model leads to an accidental global U(2)q × U(3)u × U(3)d flavour symmetry which prevents dangerously large effects in flavour observables, making a TeV extension of the SM possible. Given the structure of the PMNS matrix in the neutrino sector, we explore different possibilities for the arrangement of the leptons on the two sites, and consider different models with U(2)ℓ or U(3)ℓ flavour symmetries. The phenomenology of the models is mostly governed by a massive vector triplet of SU(2)L. We study the interesting interplay between LHC searches and precision observables. In particular, one of the models can give a sizeable lepton flavour universal effect in the Wilson coefficient C9 while naturally suppressing contributions to C10, as suggested by current b → sℓ+ℓ− data, predicting simultaneously a mild positive shift in the W boson mass.

The DUNE Far Detector Vertical Drift Technology. Technical Design Report

DUNE is an international experiment dedicated to addressing some of the questions at the forefront of particle physics and astrophysics, including themystifying preponderance of matter over antimatter in the early universe. The dual-site experiment will employ an intense neutrino beam focused on a near and a far detector as it aims to determine the neutrino mass hierarchy and to make high-precision measurements of the PMNS matrix parameters, including the CP-violating phase. It will also stand ready to observe supernova neutrino bursts, and seeks to observe nucleon decay as a signature of a grand unified theory underlying the standard model.The DUNE far detector implements liquid argon time-projection chamber (LArTPC) technology, and combines the many tens-of-kiloton fiducial mass necessary for rare event searches with the sub-centimeter spatial resolutionrequired to image those events with high precision. The addition of a photon detection system enhances physics capabilities for all DUNE physics drivers and opens prospects for further physics explorations. Given its size, the far detector will be implemented as a set of modules, with LArTPC designs that differ from one another as newer technologies arise.In the vertical drift LArTPC design, a horizontal cathode bisects the detector, creating two stacked drift volumes in which ionization charges drift towards anodes at either the top or bottom. The anodes are composed of perforated PCB layers with conductive strips, enabling reconstruction in 3D.Light-trap-style photon detection modules are placed both on the cryostat's side walls and on the central cathode where they are optically powered.This Technical Design Report describes in detail the technical implementations of each subsystem of this LArTPC that, together with the other far detector modules and the near detector, will enable DUNE to achieve its physics goals.

Maleated epoxidized natural rubber grafted cassava starch/silver composite coating for cloth glove: Preparation and physical properties

The green composite was obtained from maleated epoxidized natural rubber (MENR) latex grafted cassava starch (CS) (MNS) and silver nanoparticles (AgNPs) by using a green route process. The immersion of AgNPs in the MNS matrix was checked with UV–visible spectrometer. The SEM was applied to study the morphology of AgNPs particle. The thermal stability of the MNSAg composite increased with increasing AgNPs. The AgNPs well distributed in the MNS matrix. The silver was used to facilitate the facile and fast preparation and to improve the mechanical strength and thermal stability at 420–450 °C of the MNSAg composites. The MNSAg composite containing AgNPs exhibited excellent antibacterial activities against both Escherichia coli and Staphylococcus aureus. Moreover, it showed the high UV absorption. It was used to coat with cloth gloves. The degree of biodegradation of this sample was about 80–90 % after being buried in soil.

A new Wolfenstein-like expansion of lepton flavor mixing towards understanding its fine structure

Taking the tri-bimaximal flavor mixing pattern as a particular basis, we propose a new way to expand the 3×3 unitary Pontecorvo-Maki-Nakagawa-Sakata (PMNS) lepton flavor mixing matrix U in powers of the magnitude of its smallest element ξ≡|Ue3|≃0.149. Such a Wolfenstein-like parametrization of U allows us to easily describe the salient features and fine structures of flavor mixing and CP violation, both in vacuum and in matter.

Collimated muon beam proposal for probing neutrino charge-parity violation

AbstractThe phenomenon of neutrino oscillation is of great theoretical and experimental interest for our understand of the nature of the neutrino and its implication for physics beyond the standard Model. Currently available neutrino oscillation experiments can already constrain neutrino mixing parameters with a confidence level up to 3 standard deviations (σ). However, it remains challenging to provide a deterministic constraint on the Charge-Parity (CP) violation phase of the neutrino mixing matrix. Here, we propose an experimental setup that exploits collimated muon beams to probe neutrino CP-violation. In our proposed acceleration experiment, a 45 GeV positron source with additional muon collimation, interfaces with near-future neutrino detectors like DUNE and T2K, to probe neutrino CP-violation phase with a significantly higher sensitivity than obtained with the neutrino detectors alone, and to determine tau neutrino properties. Simulations estimate the collection of 104 tau (anti-) neutrino in 5 years, and a sensitivity of over 7 standard deviations for δCP = ∣π/2∣ in 5 years. Collecting ντ appearance events from μ− and μ+ beams over 10 years can attain a 3-4 standard deviation sensitivity. This proposal may serve as a tau factory.

Flavor invariance of leptonic Yukawa terms in the 3HDM

As an extension of the Standard Model (SM), the 3HDM (Three-Higgs-Doublet Model) defines additional relationships among the fermions. In the visible leptonic Yukawa sector of the 3HDM, we investigate the existence of flavor symmetries under discrete non-abelian groups up to order 1032. When the VEVs are not allowed to depart from their alignment imposed by the condition of minimal potential in the Higgs scalar sector, there will be severe mass degeneracies and a lack of lepton flavor mixing for any nontrivial flavor group. Yet we propose to study the Yukawa terms of the lepton sector for in case the VEV alignment would not be protected, hence leaving the VEV ratios as free parameters. Then, as it turns out, mass splitting for the charged leptons and the neutrinos is obtained although it is still impossible to obtain correct fits to the experimentally known lepton mass spectrum and to the PMNS matrix simultaneously.

On the Relations between Fermion Masses and Isospin Couplings in the Microscopic Model

AbstractQuark 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 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 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 . 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 . An outlook is given on the treatment of the CKM matrix.

Neutrino Mixing Matrix in Terms of Neutrino Mass Matrix and Its Frobenius Covariants

Neutrino Mixing Matrix in Terms of Neutrino Mass Matrix and Its Frobenius Covariants

On the Implications of |Uμi| = |Uτi| in the Canonical Seesaw Mechanism

In the PMNS matrix, the relation |Uμi| = |Uτi| (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 |Uμi| = |Uτi| (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.

From Dirac to Majorana: The cosmic neutrino background capture rate in the minimally extended Standard Model

We investigate the capture rate of the cosmic neutrino background on tritium within the Standard Model, extended to incorporate three right-handed singlet neutrinos with explicit lepton-number violation. We consider a scenario where the 6×6 neutrino mixing matrix factorizes into three independent 2×2 pairs and analyze the states produced from weak interactions just before neutrino decoupling. Taking into account the unrestricted Majorana mass scale associated with lepton number violation, spanning from the grand unification scale to Planck-suppressed values, we observe a gradual transition in the capture rate from a purely Majorana neutrino to a purely (pseudo) Dirac neutrino. We demonstrate that the capture rate is modified if the lightest active neutrino is relativistic, and this can be used to constrain the tiniest value of mass-squared difference ∼10−35 eV2, between the active-sterile pair, probed so far. Consequently, the cosmic neutrino capture rate could become a promising probe for discerning the underlying mechanism responsible for generating neutrino masses. Published by the American Physical Society 2024

Investigating CP Violating Majorana Phases of Neutrinos

Pontecorvo-Maki-Nakagawa-Sakata (PMNS) matrix is a complex symmetric matrix consisting of three generations of neutrinos and 12 real parameters. Diagonalizing the neutrino mass matrix and expressing the same in terms of three neutrino masses, three mixing angles, one Dirac phase and two Majorana phases such that it removes all the unphysical phases. The absolute neutrino mass scale and two Majorana CP-violating phases cannot be determined by neutrino oscillation experiments and hence an attempt has been made to investigate Majorana phases by drawing a correlation between the elements of neutrino mass matrix under the conditions of simultaneity and equated them to zero. We obtain twenty-five neutrino mass matrix textures for inverted hierarchy of Majorana neutrinos. Finally, numerical values of Majorana phases have been calculated for these textures and other phenomenological quantities are in consistent with the oscillation data.

Neutrino Oscillations in Finite Time Path Out-of-Equilibrium Thermal Field Theory

We demonstrate that the Finite-Time-Path Field Theory is an adequate tool for calculating neutrino oscillations. We apply this theory using a mass-mixing Lagrangian which involves the correct Dirac spin and chirality structure and a Pontecorvo–Maki–Nakagawa–Sakata (PMNS)-like mixing matrix. The model is exactly solvable. The Dyson–Schwinger equations transform propagators of the input free (massless) flavor neutrinos into a linear combination of oscillating (massive) neutrinos. The results are consistent with the predictions of the PMNS matrix while allowing for extrapolation to early times.

Thermal leptogenesis in the minimal gauged U1Lμ−Lτ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \ extrm{U}{(1)}_{L_{\\mu }-{L}_{\ au }} $$\\end{document} model

We discuss the thermal leptogenesis mechanism within the minimal gauged U1Lμ−Lτ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \ extrm{U}{(1)}_{L_{\\mu }-{L}_{\ au }} $$\\end{document} model to explain the observed baryon asymmetry of the Universe (BAU). In such framework, the phases of the Pontecorvo-Maki-Nakagawa-Sakata neutrino mixing matrix and the sum of the Standard Model neutrino masses are predictable because of a restricted neutrino mass matrix structure. Additionally, in the context of thermal leptogenesis, the BAU can be computed in terms of the three remaining free variables that parameterise the right-handed neutrino masses and their Yukawa couplings to the Higgs and lepton doublets. We identify the ranges of such parameters for which the correct BAU can be reproduced. We adopt the formalism of the density matrix equations to fully account for flavour effects and consider the decays of all the three right-handed neutrinos. Our analysis reveals that thermal leptogenesis is feasible within a wide parameter space, specifically for Yukawa couplings ranging from approximate unity to O\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{O} $$\\end{document}(0.03–0.05) and mass of the lightest right-handed neutrino M1 ≳ 1011−12 GeV, setting a leptogenesis scale in the considered model which is higher than that of the non-thermal scenario.

A Pythagoras-like theorem for CP violation in neutrino oscillations

The probabilities of νμ→νe and ν‾μ→ν‾e oscillations in vacuum are determined by the CP-conserving flavor mixing factors Rij≡Re(UμiUejUμj⁎Uei⁎) and the universal Jarlskog invariant of CP violation Jν≡(−1)i+jIm(UμiUejUμj⁎Uei⁎) (for i,j=1,2,3 and i<j), where U is the 3×3 Pontecorvo-Maki-Nakagawa-Sakata neutrino mixing matrix. We show that Jν2=R12R13+R12R23+R13R23 holds as a natural consequence of the unitarity of U. This Pythagoras-like relation may provide a novel cross-check of the result of Jν that will be directly measured in the next-generation long-baseline neutrino oscillation experiments. Indirect non-unitarity effects and terrestrial matter effects on Jν and Rij are also discussed.

A minimal axion model for mass matrices with five texture-zeros

A model with fermion and scalar fields charged under a Peccei–Queen (PQ) symmetry is proposed. The PQ charges are chosen in such a way that they can reproduce mass matrices with five texture zeros, which can generate the fermion masses, the CKM matrix, and the PMNS matrix of the Standard Model (SM). To obtain this result, at least 4 Higgs doublets are needed. As we will see in the manuscript this is a highly non-trivial result since the texture zeros of the mass matrices impose a large number of restrictions. This model shows a route to understand the different scales of the SM by extending it with a multi-Higgs sector and an additional PQ symmetry. Since the PQ charges are not universal, the model predicts flavor-changing neutral currents (FCNC) at the tree level, a feature that constitutes the main source of restrictions on the parameter space. We report the allowed regions by lepton decays and compare them with those coming from the semileptonic decays K^{pm }longrightarrow pi {bar{nu }}nu . We also show the excluded regions and the projected bounds of future experiments for the axion–photon coupling as a function of the axion mass and compare it with the parameter space of our model.

Neutrino mixing matrix and masses from a particular two-zero texture based on A 4 symmetry

The current study aims to investigate the particular case of two zeros in a Majorana neutrino mass matrix based on A 4 symmetry, where charged lepton mass matrix is diagonal. The texture is with (μ, μ) and (τ, τ) vanishing element of the neutrino mass matrix. The texture has magic and μ − τ symmetry, with a tribimaximal form of the mixing matrix, which leads to θ 13 = 0 that it is not consistent with experimental data and at first, does not seem to be allowed. Since θ 13 a small mixing angle compared to others neutrino mixing angles justifies the use of perturbation theory. We propose that, θ 13, and the Dirac phase δ, and two Majorana phases ρ and σ could be generated by using a complex symmetric perturbation mass matrix in the mass basis and find that affect to the atmospheric mixing angle. We show that only the predictions of the case I, with Δ < 0 and , are consistent with the experimental data. Furthermore, the allowed range of our parameter space and complex elements of perturbation mass matrix are found, which led to finding the allowed region of the neutrino masses, the Majorana phases, the effective neutrino mass for the neutrinoless double beta decay, the allowed deviation of θ 23 from 45°, and to predict the normal neutrino mass hierarchy. The predicted region of and θ 23 are in line with the current experimental data which indicate the accuracy of our model and its results. The results of the case II, with Δ > 0 and , are ruled out.