Articles de revues : « Dirac Neutrino Mass »

1

Hyodo, Yuta, et Teruyuki Kitabayashi. « Magic square and Dirac flavor neutrino mass matrix ». International Journal of Modern Physics A 35, n^o 29 (13 octobre 2020) : 2050183. http://dx.doi.org/10.1142/s0217751x20501833.

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The magic texture is one of the successful textures of the flavor neutrino mass matrix for the Majorana type neutrinos. The name “magic” is inspired by the nature of the magic square. We estimate the compatibility of the magic square with the Dirac, instead of the Majorana, flavor neutrino mass matrix. It turned out that some parts of the nature of the magic square are appeared approximately in the Dirac flavor neutrino mass matrix and the magic squares prefer the normal mass ordering rather than the inverted mass ordering for the Dirac neutrinos.

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Matute, Ernesto A. « Low-scale minimal linear seesaw model for neutrino mass and flavor mixing ». Modern Physics Letters A 36, n^o 22 (19 juillet 2021) : 2150159. http://dx.doi.org/10.1142/s0217732321501595.

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We consider an extension of the Standard Model with three right-handed (RH) neutrinos and a Dirac pair of extra sterile neutrinos, odd under a discrete [Formula: see text] symmetry, in order to have left–right symmetry in the neutrino content and obtain tiny neutrino masses from the latter ones only. Our working hypothesis is that the heavy RH neutrinos do not influence phenomenology at low energies. We use the usual high-scale seesaw to suppress all of the mass terms involving RH neutrinos and a low-scale minimal variant of the linear seesaw led by the Dirac mass of the extra sterile neutrinos to provide the small mass of active neutrinos. One of the active neutrinos is massless, which fixes the mass of the other two on the basis of a soft breaking of the [Formula: see text] symmetry. The mixing between the extra neutrinos makes for a particle that effectively behaves like a Dirac sterile neutrino with mass around the GeV level.

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Matute, Ernesto A. « Neutrino mass generation with extra right-handed fields in a Dirac scenario via the type-I seesaw mechanism ». Modern Physics Letters A 29, n^o 40 (28 décembre 2014) : 1450212. http://dx.doi.org/10.1142/s0217732314502125.

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An extension of the Standard Model (SM) is studied in which two right-handed (RH) neutrinos per generation are incorporated, but considering the hypothesis of the symmetry of lepton and quark contents in order to deprive the number of RH neutrinos of freedom, generate Dirac neutrinos and accommodate naturally tiny values for their masses. The high scale type-I seesaw regime is applied to the first, ordinary RH neutrino, whereas a low scale pseudo-Dirac scenario is used for the second, adulterant RH neutrino, implying that the first RH neutrino decouples at the high scale, while the second RH neutrino survives down to the low scale to pair off in a Dirac-like form with the corresponding left-handed (LH) neutrino. The small mass and couplings of this extra RH neutrino are explained by means of the statement of the symmetry of fermionic content, only regarded as a guideline to the natural choice of parameters since it is not a proper symmetry in the Lagrangian.

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Petcov, S. T. « Leptonic CP violation and leptogenesis ». International Journal of Modern Physics A 29, n^o 11n12 (25 avril 2014) : 1430028. http://dx.doi.org/10.1142/s0217751x14300282.

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The phenomenology of 3-neutrino mixing, the current status of our knowledge about the 3-neutrino mixing parameters, including the absolute neutrino mass scale, and of the Dirac and Majorana CP violation in the lepton sector, are reviewed. The problems of CP violation in neutrino oscillations and of determining the nature — Dirac or Majorana — of massive neutrinos, are discussed. The seesaw mechanism of neutrino mass generation and the related leptogenesis scenario of generation of the baryon asymmetry of the universe, are considered. The results showing that the CP violation necessary for the generation of the baryon asymmetry of the universe in leptogenesis can be due exclusively to the Dirac and/or Majorana CP-violating phase(s) in the neutrino mixing matrix U, are briefly reviewed.

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Peinado, Eduardo, Mario Reig, Rahul Srivastava et Jose W. F. Valle. « Dirac neutrinos from Peccei–Quinn symmetry : A fresh look at the axion ». Modern Physics Letters A 35, n^o 21 (29 mai 2020) : 2050176. http://dx.doi.org/10.1142/s021773232050176x.

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We show that a very simple solution to the strong CP problem naturally leads to Dirac neutrinos. Small effective neutrino masses emerge from a type-I Dirac seesaw mechanism. Neutrino mass limits probe the axion parameters in regions currently inaccessible to conventional searches.

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RAJPOOT, SUBHASH. « MASSIVE DIRAC NEUTRINOS AND SN1987A ». Modern Physics Letters A 08, n^o 13 (30 avril 1993) : 1179–84. http://dx.doi.org/10.1142/s021773239300266x.

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If neutrinos are massive Dirac particles, their right-handed components are inert to interactions with matter. However, the helicity flip mechanism due to the mass term can participate in the cooling of a new born star. The observed neutrino bursts from SN1987A constrained Dirac neutrino masses to lie between 1 keV and 10 keV so as to avoid rapid cooling due to the mass induced helicity flip mechanism. We suggest scalar particle mediated new interactions between the right-handed neutrinos and nuclear matter that trap the right-handed neutrinos long enough so that the total energy of the exploding star is carried away predominantly by left-handed neutrinos. The bounds from cosmology are also shown to be satisfied.

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FRAMPTON, P. H. « ASPECTS OF NEUTRINO MASS MATRICES ». International Journal of Modern Physics A 20, n^o 06 (10 mars 2005) : 1188–96. http://dx.doi.org/10.1142/s0217751x05024079.

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After an Introduction briefly describing the rise and fall of the three-zero texture of the Zee model, we discuss still-allowed two-zero textures for the Majorana three-neutrino mass matrix. Finally, a model with two right-handed neutrinos and two Dirac texture zeros is described (FGY model) which can relate CP violation in leptogenesis to CP violation in long-baseline neutrino oscillations.

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Matute, Ernesto A. « Neutrino mass generation from the perspective of presymmetry ». Modern Physics Letters A 34, n^o 34 (5 novembre 2019) : 1950284. http://dx.doi.org/10.1142/s0217732319502845.

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The Standard Model (SM) with one right-handed neutrino per generation is revisited with presymmetry being the global [Formula: see text] symmetry of an electroweak theory of leptons and quarks with initially postulated symmetric fractional charges. The cancellation of gauge anomalies and the non-perturbative normalization of lepton charges proceed through the mixing of local and topological charges, the global [Formula: see text] measuring the induced charge associated with a unit of topological charge, and the mathematical replacement of the original fractional charges with the experimentally observed ones. The [Formula: see text] symmetry of the SM with Dirac neutrinos is seen as a residual presymmetry. High-scale and low-scale seesaw mechanisms proposed to explain the mass of neutrinos are examined from the perspective of presymmetry, be they of Majorana or pseudo-Dirac type. We find that the tiny mass splitting in pseudo-Dirac neutrinos and the mass of heavy neutrinos ride on the opposite ends of the seesaw. We show that pseudo-Dirac neutrinos contain extra sterile neutrinos with imprints of presymmetry and for heavy ones we get constraints favoring the low-scale linear seesaw over the inverse variant.

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Nicolaidis, Argyris. « Neutrinos and the structure of space-time ». Facta universitatis - series : Physics, Chemistry and Technology 12, n^o 2 (2014) : 179–88. http://dx.doi.org/10.2298/fupct1402179n.

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The phenomenon of neutrino oscillations is studied usually as a mixing between the flavor neutrinos and the neutrinos having a definite mass. The mixing angles and the mass eigenvalues are treated independently in order to accommodate the experimental data. We suggest that neutrino oscillations are connected to the structure of spacetime. We expand on a recently proposed model, where two ?mirror? branes coexist. One brane hosts left-handed particles (our brane), while the other brane hosts right-handed particles. Majorana-type couplings mixes neutrinos in an individual brane, while Dirac-type couplings mixes neutrinos across the brares. We first focus our attention in a single brane. The mass matrix, determined by the Majorana mass, leads to mass eigenstates and further to mixing angles identical to the mixing angles proposed by the tri-bimaximal mixing. When we include the Dirac-type coupling, connecting the two branes, we obtain a definite prediction for the transition to a sterile neutrino (righthanded neutrino). With mL (mR) the Majorana mass for the left (right) brane, we are able to explain the solar and the atmospheric neutrino data with mL = 2mR and mR = 10-2 eV.

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BELL, N. F. « HOW MAGNETIC IS THE NEUTRINO ? » International Journal of Modern Physics A 22, n^o 27 (30 octobre 2007) : 4891–99. http://dx.doi.org/10.1142/s0217751x07038256.

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The existence of a neutrino magnetic moment implies contributions to the neutrino mass via radiative corrections. We derive model-independent "naturalness" upper bounds on the magnetic moments of Dirac and Majorana neutrinos, generated by physics above the electroweak scale. For Dirac neutrinos, the bound is several orders of magnitude more stringent than present experimental limits. However, for Majorana neutrinos the magnetic moment bounds are weaker than present experimental limits if μν is generated by new physics at ~ 1 TeV , and surpass current experimental sensitivity only for new physics scales > 10 – 100 TeV . The discovery of a neutrino magnetic moment near present limits would thus signify that neutrinos are Majorana particles.

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Ahuja, Gulsheen, et Manmohan Gupta. « Texture zero mass matrices and nature of neutrinos ». International Journal of Modern Physics A 33, n^o 31 (10 novembre 2018) : 1844032. http://dx.doi.org/10.1142/s0217751x18440323.

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For Majorana as well as Dirac neutrinos, attempt has been made to carry out a comparative study of the predictions of Fritzsch-like texture 6, 5 and 4 zero leptonic mass matrices. In particular, considering normal hierarchy of neutrino masses, we have examined how the parameter space available to the mixing angles with respect to the lightest neutrino mass changes for the two types of neutrinos.

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Nieuwenhuizen, Theodorus Maria. « The Standard Model of Particle Physics with Diracian Neutrino Sector ». Symmetry 11, n^o 8 (3 août 2019) : 994. http://dx.doi.org/10.3390/sym11080994.

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The minimally extended standard model of particle physics contains three right handed or sterile neutrinos, coupled to the active ones by a Dirac mass matrix and mutually by a Majorana mass matrix. In the pseudo-Dirac case, the Majorana terms are small and maximal mixing of active and sterile states occurs, which is generally excluded for solar neutrinos. In a “Diracian” limit, the physical masses become pairwise degenerate and the neutrinos attain a Dirac signature. Members of a pair do not oscillate mutually so that their mixing can be undone, and the standard neutrino model follows as a limit. While two Majorana phases become physical Dirac phases and three extra mass parameters occur, a better description of data is offered. Oscillation problems are worked out in vacuum and in matter. With lepton number –1 assigned to the sterile neutrinos, the model still violates lepton number conservation and allows very feeble neutrinoless double beta decay. It supports a sterile neutrino interpretation of Earth-traversing ultra high energy events detected by ANITA.

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MCDONALD, K. L., et B. H. J. MCKELLAR. « THE TYPE-II SINGULAR SEE-SAW MECHANISM ». International Journal of Modern Physics A 22, n^o 12 (10 mai 2007) : 2211–22. http://dx.doi.org/10.1142/s0217751x07036567.

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The singular see-saw mechanism is a variation of the see-saw mechanism whereby the right-chiral neutrino Majorana mass matrix is singular. Previous works employing the singular see-saw mechanism have assumed a vanishing left-chiral Majorana mass matrix. We study the neutrino spectrum obtained under a singular see-saw mechanism when the left-chiral neutrinos possess a nonzero Majorana mass matrix. We refer to this as the type-II singular see-saw mechanism. The resulting neutrino spectrum is found to be sensitive to the hierarchy of the Dirac and Majorana mass scales used and we explore the phenomenological consequences of the candidate hierarchies. The compatibility of the resulting spectra with the body of neutrino oscillation data is discussed. It is found that neutrino mass matrices with this structure result in 3+1 or 2+2 neutrino spectra, making it unlikely that this mass matrix structure is realized in nature. If the left-chiral Majorana mass matrix is also singular we show that a type-II singular see-saw mechanism can realize a spectrum of one active-sterile pseudo-Dirac neutrino in conjunction with two active Majorana neutrinos effectively decoupled from the sterile sector. This realizes a scheme discussed in the literature in relation to astrophysical neutrino fluxes.

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Dvornikov, Maxim. « Neutrino interaction with background matter in a non-inertial frame ». Modern Physics Letters A 30, n^o 23 (20 juillet 2015) : 1530017. http://dx.doi.org/10.1142/s0217732315300177.

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We study Dirac neutrinos propagating in rotating background matter. First we derive the Dirac equation for a single massive neutrino in the non-inertial frame, where matter is at rest. This equation is written in the effective curved spacetime corresponding to the co-rotating frame. We find the exact solution of the Dirac equation. The neutrino energy levels for ultrarelativistic particles are obtained. Then we discuss several neutrino mass eigenstates, with a nonzero mixing between them, interacting with rotating background matter. We derive the effective Schrödinger equation governing neutrino flavor oscillations in rotating matter. The new resonance condition for neutrino oscillations is obtained. We also examine the correction to the resonance condition caused by the matter rotation.

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DIVAKARAN, P. P., et G. RAJASEKARAN. « A NEW MECHANISM FOR NEUTRINO MASS ». Modern Physics Letters A 14, n^o 14 (10 mai 1999) : 913–17. http://dx.doi.org/10.1142/s0217732399000973.

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A mechanism for generating massive but naturally light Dirac neutrinos is proposed. It involves composite Higgs within the standard model as well as some new interaction beyond the standard model. According to this scenario, a neutrino mass of 0.1 eV or higher, signals new physics at energies of 10–100 TeV or lower.

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Arbeláez, C., C. Dib, K. Monsálvez-Pozo et I. Schmidt. « Quasi-Dirac neutrinos in the linear seesaw model ». Journal of Physics : Conference Series 2156, n^o 1 (1 décembre 2021) : 012220. http://dx.doi.org/10.1088/1742-6596/2156/1/012220.

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Abstract We implement a minimal linear seesaw model (LSM) for addressing the Quasi-Dirac (QD) behaviour of heavy neutrinos, focusing on the mass regime of MN ≲ MW . Here we show that for relatively low neutrino masses, covering the few GeV range, the same-sign to opposite-sign dilepton ratio, Rℓ, can be anywhere between 0 and 1, thus signaling a Quasi-Dirac regime. Particular values of Rℓ are controlled by the width of the QD neutrino and its mass splitting, the latter being equal to the light-neutrino mass mυ in the LSM scenario. The current upper bound on m υ1 together with the projected sensitivities of current and future |UNℓ |2 experimental measurements, set stringent constraints on our low-scale QD mass regime. Some experimental prospects of testing the model by LHC displaced vertex searches are also discussed.

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PAKVASA, SANDIP. « NEUTRINO FLAVOR GONIOMETRY BY HIGH ENERGY ASTROPHYSICAL BEAMS ». Modern Physics Letters A 23, n^o 17n20 (28 juin 2008) : 1313–24. http://dx.doi.org/10.1142/s0217732308027680.

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It is shown how high energy neutrino beams from very distant sources can be utilized to learn about many properties of neutrinos such as lifetimes, mass hierarchy, mixing, minuscule pseudo-Dirac mass splittings and other exotic properties; in addition, the production mechanism of neutrinos in astrophysical sources can also be elucidated.

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LIU, XUE-WEN, et SHUN ZHOU. « TEXTURE ZEROS FOR DIRAC NEUTRINOS AND CURRENT EXPERIMENTAL TESTS ». International Journal of Modern Physics A 28, n^o 12 (5 mai 2013) : 1350040. http://dx.doi.org/10.1142/s0217751x13500401.

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The Daya Bay and RENO reactor neutrino experiments have revealed that the smallest neutrino mixing angle is in fact relatively large, i.e. θ13 ≈9°. Motivated by this exciting progress, we perform a systematic study of the neutrino mass matrix Mν with one or two texture zeros, in the assumption that neutrinos are Dirac particles. Among 15 possible patterns with two texture zeros, only three turn out to be favored by current neutrino oscillation data at the 3σ level. Although all the six patterns with one texture zero are compatible with the experimental data at the 3σ level, the parameter space of each pattern is strictly constrained. Phenomenological implications of Mν on the leptonic CP violation and neutrino mass spectrum are explored, and the stability of texture zeros against the radiative corrections is also discussed.

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JOSHIPURA, ANJAN S. « 17 keV NEUTRINO AND MAJORON MODELS ». International Journal of Modern Physics A 07, n^o 09 (10 avril 1992) : 2021–31. http://dx.doi.org/10.1142/s0217751x92000892.

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A model for the 17 keV Dirac neutrino is considered in the framework of the SU(2) × U(1) theory. No right-handed neutrinos are introduced. The Dirac mass for the neutrino arises from the Le+Lτ–Lμ invariant couplings of the left-handed neutrinos to an SU(2) triplet. An SU(2) singlet field is introduced to suppress the Majoron coupling to the Z. This makes the model consistent with the LEP results on the invisible Z width. The singlet vacuum expectation value ω is constrained to be ≤O(80 MeV) from cosmological considerations. For, ω≈80 MeV, the 17 keV neutrino is shown to provide the bulk of the dark matter.

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Lu, Jianlong, Aik Hui Chan et Choo Hiap Oh. « A Phenomenological Model of Effectively Oscillating Massless Neutrinos and Its Implications ». EPJ Web of Conferences 240 (2020) : 02002. http://dx.doi.org/10.1051/epjconf/202024002002.

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We discuss an alternative picture of neutrino oscillation. In this phenomenological model, the flavor-changing phenomena of massless neutrinos arise from scattering processes between neutrinos and four types of undetected spin-0 massive particles pervading throughout the Universe, instead of neutrinos’ own nature. These scattering processes are kinematically similar to Compton scattering. One type of left-handed massless sterile neutrino is needed in order to reproduce the neutrino oscillation modes predicted in the theory of neutrino mixing. Implications of our model include the existence of sterile neu- trinos, the nonconservation of active neutrinos, the possible mismatch among three neutrino mass squared diﬀerences ∆m2ij interpreted in the theory of neutrino mixing, the spacetime dependence of neutrino oscillation, and the impossibility of neutrinoless double beta decay. Several important open problems in neutrino physics become trivial or less severe in our model, such as the smallness of neutrino masses, neutrino mass hierarchy, the mechanism responsible for neutrino masses, and the Dirac/Majorana nature of neutrinos.

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PAKVASA, SANDIP. « NEUTRINO PROPERTIES FROM HIGH ENERGY ASTROPHYSICAL NEUTRINOS ». Modern Physics Letters A 19, n^o 13n16 (30 mai 2004) : 1163–69. http://dx.doi.org/10.1142/s0217732304014513.

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It is shown how high energy neutrino beams from very distant sources can be utilized to yield information about properties of neutrinos such as lifetimes and the possible mass hierarchy.Furthermore, mixing elements such as Ue3 and the CPV phase in the neutrino mixing matrix can be determined in principle. Pseudo-Dirac mass differences as small as 10-18eV2 can be probed as well.

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LIPMANOV, E. M. « ν-K0 ANALOGY, DIRAC–MAJORANA NEUTRINO DUALITY AND THE NEUTRINO OSCILLATIONS ». International Journal of Modern Physics A 16, n^o 30 (10 décembre 2001) : 4911–23. http://dx.doi.org/10.1142/s0217751x01005675.

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The intent of this paper is to convey a new primary physical idea of a Dirac–Majorana neutrino duality in relation to the topical problem of neutrino oscillations. In view of the new atmospheric, solar and the LSND neutrino oscillation data, the Pontecorvo ν - K0 oscillation analogy is generalized to the notion of neutrino duality with substantially different physical meaning ascribed to the long-baseline and the short-baseline neutrino oscillations. At the level of CP-invariance, the suggestion of dual neutrino properties defines the symmetric two-mixing-angle form of the widely discussed four-neutrino (2 +2)-mixing scheme, as a result of the lepton charge conservation selection rule and a minimum of two Dirac neutrino fields. With neutrino duality, the two-doublet structure of the Majorana neutrino mass spectrum is a vestige of the two-Dirac-neutrino origin. The fine neutrino mass doublet structure is natural because it is produced by a lepton charge symmetry violating perturbation on a zero-approximation system of two twofold mass-degenerate Dirac neutrino–antineutrino pairs. A set of inferences related to the neutrino oscillation phenomenology in vacuum is considered.

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PATGIRI, MAHADEV, et N. NIMAI SINGH. « RIGHT-HANDED MAJORANA NEUTRINO MASS MATRICES FOR GENERATING BIMAXIMAL MIXINGS IN DEGENERATE AND INVERTED MODELS OF NEUTRINOS ». International Journal of Modern Physics A 18, n^o 05 (20 février 2003) : 743–53. http://dx.doi.org/10.1142/s0217751x03014022.

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An attempt is made to generate the bimaximal mixings of the three species of neutrinos from the textures of the right-handed Majorana neutrino mass matrices. We extend our earlier work in this paper for the generation of the nearly degenerate as well as the inverted hierarchical models of the left-handed Majorana neutrino mass matrices using the non-diagonal textures of the right-handed Majorana neutrino mass matrices and the diagonal form of Dirac neutrino mass matrices, within the framework of the see-saw mechanism in a model independent way. Such Majorana neutrino mass models are important in explaining the recently reported result on the neutrinoless double beta decay (0νββ) experiment, together with the earlier established data on LMA MSW solar and atmospheric neutrino oscillations.

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Chowdhury, Talal Ahmed, Md Ehsanuzzaman et Shaikh Saad. « Dark Matter and (g - 2)_μ,e in radiative Dirac neutrino mass models ». Journal of Cosmology and Astroparticle Physics 2022, n^o 08 (1 août 2022) : 076. http://dx.doi.org/10.1088/1475-7516/2022/08/076.

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

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Buccella, F., et D. Falcone. « Bounds for the Mass of the Heaviest Right-Handed Neutrino in SO(10) Theories ». Modern Physics Letters A 18, n^o 26 (30 août 2003) : 1819–23. http://dx.doi.org/10.1142/s0217732303011757.

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By relating the Dirac neutrino mass matrix to the mass of the charged fermions and assuming that the product of the masses of the two lightest left-handed neutrinos is of the order of [Formula: see text], we derive, within a leptogenesis scenario, a range of values for the mass of the heaviest right-handed neutrino, centered around the scale of B–L symmetry breaking in the SO(10) theory with Pati–Salam intermediate symmetry.

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Benaoum, H. B., et S. H. Shaglel. « TeV-scale resonant leptogenesis with new scaling ansatz on neutrino Dirac mass matrix from A4 flavor symmetry ». International Journal of Modern Physics A 35, n^o 17 (12 juin 2020) : 2050077. http://dx.doi.org/10.1142/s0217751x20500773.

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We propose a new scaling ansatz in the neutrino Dirac mass matrix to explain the low energy neutrino oscillations data, baryon number asymmetry and neutrinoless double beta decay. In this work, a full reconstruction of the neutrino Dirac mass matrix has been realized from the low energy neutrino oscillations data based on type-I seesaw mechanism. A concrete model based on [Formula: see text] flavor symmetry has been considered to generate such a neutrino Dirac mass matrix and imposes a relation between the two scaling factors. In this model, the right-handed Heavy Majorana neutrino masses are quasi-degenerate at TeV mass scales. Extensive numerical analysis studies have been carried out to constrain the parameter space of the model from the low energy neutrino oscillations data. It has been found that the parameter space of the Dirac mass matrix elements lies near or below the MeV region and the scaling factor [Formula: see text] has to be less than 10. Furthermore, we have examined the possibility for simultaneous explanation of both neutrino oscillations data and the observed baryon number asymmetry in the Universe. Such an analysis gives further restrictions on the parameter space of the model, thereby explaining the correct neutrino data as well as the baryon number asymmetry via a resonant leptogenesis scenario. Finally, we show that the allowed space for the effective Majorana neutrino mass [Formula: see text] is also constrained in order to account for the observed baryon asymmetry.

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Vien, V. V. « Lepton mass and mixing in a neutrino mass model based onS4flavor symmetry ». International Journal of Modern Physics A 31, n^o 09 (24 mars 2016) : 1650039. http://dx.doi.org/10.1142/s0217751x16500391.

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We study a neutrino mass model based on [Formula: see text] flavor symmetry which accommodates lepton mass, mixing with nonzero [Formula: see text] and CP violation phase. The spontaneous symmetry breaking in the model is imposed to obtain the realistic neutrino mass and mixing pattern at the tree-level with renormalizable interactions. Indeed, the neutrinos get small masses from one [Formula: see text] doublet and two [Formula: see text] singlets in which one being in [Formula: see text] and the two others in [Formula: see text] under [Formula: see text] with both the breakings [Formula: see text] and [Formula: see text] are taken place in charged lepton sector and [Formula: see text] in neutrino sector. The model also gives a remarkable prediction of Dirac CP violation [Formula: see text] or [Formula: see text] in both the normal and inverted spectrum which is still missing in the neutrino mixing matrix. The relation between lepton mixing angles is also represented.

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Petcov, S. T. « The Nature of Massive Neutrinos ». Advances in High Energy Physics 2013 (2013) : 1–20. http://dx.doi.org/10.1155/2013/852987.

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The compelling experimental evidences for oscillations of solar, reactor, atmospheric, and accelerator neutrinos imply the existence of 3-neutrino mixing in the weak charged lepton current. The current data on the 3-neutrino mixing parameters are summarised and the phenomenology of 3-νmixing is reviewed. The properties of massive Majorana neutrinos and of their various possible couplings are discussed in detail. Two models of neutrino mass generation with massive Majorana neutrinos—the type I see-saw and the Higgs triplet model—are briefly reviewed. The problem of determining the nature, Dirac or Majorana, of massive neutrinos is considered. The predictions for the effective Majorana mass|〈m〉|in neutrinoless double-beta-((ββ)0ν-) decay in the case of 3-neutrino mixing and massive Majorana neutrinos are summarised. The physics potential of the experiments, searching for(ββ)0ν-decay for providing information on the type of the neutrino mass spectrum, on the absolute scale of neutrino masses, and on the Majorana CP-violation phases in the PMNS neutrino mixing matrix, is also briefly discussed. The opened questions and the main goals of future research in the field of neutrino physics are outlined.

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XING, ZHI-ZHONG. « FLAVOR MIXING AND CP VIOLATION OF MASSIVE NEUTRINOS ». International Journal of Modern Physics A 19, n^o 01 (10 janvier 2004) : 1–79. http://dx.doi.org/10.1142/s0217751x04016969.

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We present an overview of recent progress in the phenomenological study of neutrino masses, lepton flavor mixing and CP violation. We concentrate on the model-independent properties of massive neutrinos, both in vacuum and in matter. Current experimental constraints on the neutrino mass spectrum and the lepton flavor mixing parameters are summarized. The Dirac- and Majorana-like phases of CP violation, which are associated respectively with the long-baseline neutrino oscillations and the neutrinoless double beta decay, are discussed in detail. The seesaw mechanism, the leptogenesis scenario and the strategies to construct lepton mass matrices are briefly described. The features of flavor mixing between one sterile neutrino and three active neutrinos are also explored.

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Gautam, Nayana, et Mrinal Kumar Das. « Neutrino mass, leptogenesis and sterile neutrino dark matter in inverse seesaw framework ». International Journal of Modern Physics A 36, n^o 21 (30 juillet 2021) : 2150146. http://dx.doi.org/10.1142/s0217751x21501463.

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

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31

Leung, C. N. « Majorana mass term, Dirac neutrinos and selective neutrino oscillations ». Zeitschrift für Physik C Particles and Fields 35, n^o 4 (décembre 1987) : 533–36. http://dx.doi.org/10.1007/bf01596906.

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Nanni, L. « Dynamics of neutrino wave packet in the Tachyon-like Dirac equation ». Revista Mexicana de Física 66, n^o 4 Jul-Aug (1 juillet 2020) : 424. http://dx.doi.org/10.31349/revmexfis.66.424.

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In this study the tachyon-like Dirac equation, formulated by Chodos to describe superluminal neutrino, is solved. The analytical solutions are Gaussian wave packets obtained using the envelope method. It is shown that the superluminal neutrino behaves like a pseudo-tachyon, namely a particle with subluminal velocity and pure imaginary mass that fulfils the energy-momentum relation typical of classical tachyons. The obtained results are used to prove that the trembling motion of the particle position around the median, known as Zitterbewegung, also takes place for the superluminal neutrino, even if the oscillation velocity is always lower than the speed of light. Finally, the pseudo-tachyon wave packet is used to calculate the probability of oscillation between mass states, obtaining a formula analogous to the one obtained for the ordinary neutrino. This suggest that in the experiments concerning neutrino oscillation is not possible to distinguish tachyonic neutrinos from ordinary ones.

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LI, XUEQIAN, et ZHIJIAN TAO. « NEUTRINO COUNTING WITH ONE (OR MORE) RIGHT-HANDED MAJORANA NEUTRINO ». Modern Physics Letters A 05, n^o 24 (30 septembre 1990) : 1933–40. http://dx.doi.org/10.1142/s0217732390002195.

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The recent data of ALEPH and L3 collaborations seem to indicate that the generation number is likely to be three based on the normal formula. However, we show that if one or several SU(2) singlet heavy neutrinos with both the Dirac and Majorana mass terms exist, mixing with light neutrinos can cause some variations in the neutrino counting formulation and the results imply that if the extra neutrinos are very heavy, the fourth generation is not ruled out by the present data.

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Chang, Darwin, et Rabindra N. Mohapatra. « Small and calculable Dirac neutrino mass ». Physical Review Letters 58, n^o 16 (20 avril 1987) : 1600–1603. http://dx.doi.org/10.1103/physrevlett.58.1600.

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Saad, Shaikh. « Simplest radiative Dirac neutrino mass models ». Nuclear Physics B 943 (juin 2019) : 114636. http://dx.doi.org/10.1016/j.nuclphysb.2019.114636.

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Ma, Ernest, et Utpal Sarkar. « Radiative left-right Dirac neutrino mass ». Physics Letters B 776 (janvier 2018) : 54–57. http://dx.doi.org/10.1016/j.physletb.2017.08.071.

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Jana, Sudip, Yago P. Porto-Silva et Manibrata Sen. « Exploiting a future galactic supernova to probe neutrino magnetic moments ». Journal of Cosmology and Astroparticle Physics 2022, n^o 09 (1 septembre 2022) : 079. http://dx.doi.org/10.1088/1475-7516/2022/09/079.

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Abstract A core-collapse supernova (SN) offers an excellent astrophysical laboratory to test non-zero neutrino magnetic moments. In particular, the neutronization burst phase, which lasts for a few tens of milliseconds post-bounce, is dominated by electron neutrinos and can offer exceptional discovery potential for transition magnetic moments. We simulate the neutrino spectra from the burst phase in forthcoming neutrino experiments like the Deep Underground Neutrino Experiment (DUNE), and the Hyper-Kamiokande (HK), by taking into account spin-flavour conversions of supernova neutrinos caused by interactions with ambient magnetic fields. We find that the sensitivities to neutrino transition magnetic moments which can be explored by these experiments for a galactic SN are an order to several orders of magnitude better than the current terrestrial and astrophysical limits. Additionally, we also discuss how this realization might provide light on three important neutrino properties: (a) the Dirac/Majorana nature, (b) the neutrino mass ordering, and (c) the neutrino mass-generation mechanism.

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Kim, Y. S., G. Q. Maguire et M. E. Noz. « Do Small-Mass Neutrinos Participate in Gauge Transformations ? » Advances in High Energy Physics 2016 (2016) : 1–7. http://dx.doi.org/10.1155/2016/1847620.

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Neutrino oscillation experiments presently suggest that neutrinos have a small but finite mass. If neutrinos have mass, there should be a Lorentz frame in which they can be brought to rest. This paper discusses how Wigner’s little groups can be used to distinguish between massive and massless particles. We derive a representation of theSL(2,c)group which separates out the two sets of spinors: one set is gauge dependent and the other set is gauge invariant and represents polarized neutrinos. We show that a similar calculation can be done for the Dirac equation. In the large-momentum/zero-mass limit, the Dirac spinors can be separated into large and small components. The large components are gauge invariant, while the small components are not. These small components represent spin-1/2non-zero-mass particles. If we renormalize the large components, these gauge invariant spinors represent the polarization of neutrinos. Massive neutrinos cannot be invariant under gauge transformations.

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Chianese, Marco, Damiano F. G. Fiorillo, Gennaro Miele et Stefano Morisi. « Investigating two heavy neutral leptons neutrino seesaw mechanism at SHiP ». International Journal of Modern Physics A 34, n^o 08 (20 mars 2019) : 1950047. http://dx.doi.org/10.1142/s0217751x19500477.

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One of the main purposes of SHiP experiment is to shed light on neutrino mass generation mechanisms like the so-called seesaw. We consider a minimal type-I seesaw neutrino mass mechanism model with two heavy neutral leptons (right-handed or sterile neutrinos) with arbitrary masses. Extremely high active-sterile mixing angle requires a correlation between the phases of the Dirac neutrino couplings. Actual experimental limits on the half-life of neutrinoless double beta decay [Formula: see text]-rate on the active-sterile mixing angle are not significative in constraining the masses or the mixing measurable by SHiP.

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SIDHARTH, B. G. « THE MASS OF THE NEUTRINOS ». International Journal of Modern Physics E 19, n^o 11 (novembre 2010) : 2285–92. http://dx.doi.org/10.1142/s021830131001665x.

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In the theory of the Dirac equation and in the standard model, the neutrino is massless. Both these theories use Lorentz invariance. In modern approaches however, spacetime is no longer smooth, and this modifies special relativity. We show how such a modification throws up the mass of the neutrino.

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Esposito, Salvatore, et Nicola Tancredi. « Pontecorvo Neutrino–Antineutrino Oscillations : Theory and Experimental Limits ». Modern Physics Letters A 12, n^o 25 (20 août 1997) : 1829–38. http://dx.doi.org/10.1142/s0217732397001862.

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We study Pontecorvo neutrino–antineutrino oscillations both in vacuum and in matter within a field theoretic approach, showing that this phenomenon can occur only if neutrinos have a Dirac–Majorana mass term. We find that matter effects suppress these oscillations and cannot explain the solar neutrino problem. On the contrary, a vacuum neutrino–antineutrino oscillations solution to this problem exists. We analyze this solution and the available data from laboratory experiments giving stringent limits on νe and νμ Majorana masses.

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Xing, Zhi-Zhong. « Majorana phases and neutrino–antineutrino oscillations ». International Journal of Modern Physics A 29, n^o 21 (20 août 2014) : 1444003. http://dx.doi.org/10.1142/s0217751x14440035.

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If massive neutrinos are the Majorana particles, how to pin down the Majorana CP-violating phases will eventually become an unavoidable question relevant to the future neutrino experiments. I argue that a study of neutrino–antineutrino oscillations will greatly help in this regard, although the issue remains purely academic at present. In this talk I first derive the probabilities and CP-violating asymmetries of neutrino–antineutrino oscillations in the three-flavor framework, and then illustrate their properties in two special cases: the normal neutrino mass hierarchy with m1 = 0 and the inverted neutrino mass hierarchy with m3 = 0. I demonstrate the significant contributions of the Majorana phases to the CP-violating asymmetries, even in the absence of the Dirac phase.

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Borah, Debasish. « Type II seesaw origin of nonzero θ13, δCP and leptogenesis ». International Journal of Modern Physics A 29, n^o 22 (29 août 2014) : 1450108. http://dx.doi.org/10.1142/s0217751x14501085.

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We discuss the possible origin of nonzero reactor mixing angle θ13 and Dirac CP phase δ CP in the leptonic sector from a combination of type I and type II seesaw mechanisms. Type I seesaw contribution to neutrino mass matrix is of tri-bimaximal (TBM) type which gives rise to vanishing θ13 leaving the Dirac CP phase undetermined. If the Dirac neutrino mass matrix is assumed to take the diagonal charged lepton (CL) type structure, such a TBM type neutrino mass matrix originating from type I seesaw corresponds to real values of Dirac Yukawa couplings in the terms [Formula: see text]. This makes the process of right-handed heavy neutrino decay into a light neutrino and Higgs (N → νH) CP preserving ruling out the possibility of leptogenesis. Here we consider the type II seesaw term as the common origin of nonzero θ13 and δ CP by taking it as a perturbation to the leading order TBM type neutrino mass matrix. First, we numerically fit the type I seesaw term by taking oscillation as well as cosmology data and then compute the predictions for neutrino parameters after the type II seesaw term is introduced. We consider a minimal structure of the type II seesaw term and check whether the predictions for neutrino parameters lie in the 3σ range. We also compute the predictions for baryon asymmetry of the universe by considering type II seesaw term as the only source of CP violation and compare it with the latest cosmology data.

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Francis, Ng K., et Ankur Nath. « The Effects of Majorana Phases in Estimating the Masses of Neutrinos ». International Journal of Modern Physics : Conference Series 47 (janvier 2018) : 1860100. http://dx.doi.org/10.1142/s201019451860100x.

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Majorana CP violating phases coming from heavy right-handed Majorana mass matrices([Formula: see text]) are considered to estimate the masses of neutrinos. The effects of phases on quasi-degenerate neutrinos mass matrix obeying [Formula: see text] symmetry predicts the results consistent with observations for (i) solar mixing angle([Formula: see text]) below TBM, (ii) absolute neutrino mass parameters[[Formula: see text]] in neutrinoless double beta([Formula: see text]) decay, and (iii) cosmological upper bound [Formula: see text]. Analysis is carried out through parameterization of light left-handed Majorana neutrino matrices ([Formula: see text]) using only two unknown parameters ([Formula: see text]) within [Formula: see text] symmetry. We consider the charge lepton and up quark matrices as diagonal form of Dirac neutrino mass matrix ([Formula: see text]), and [Formula: see text] are generated using [Formula: see text] through inversion of Type-I seesaw formula. The analysis shows that the masses of neutrinos are in agreement with the upper bound from cosmology and neutrinoless double beta decay. The results presented in this article will have important implications in discriminating the neutrinos mass models.

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Khatun, Amina, Adam Smetana et Fedor Šimkovic. « Three Flavor Quasi-Dirac Neutrino Mixing, Oscillations and Neutrinoless Double Beta Decay ». Symmetry 12, n^o 8 (5 août 2020) : 1310. http://dx.doi.org/10.3390/sym12081310.

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The extension of the Standard model by three right-handed neutrino fields exhibit appealing symmetry between left-handed and right-handed sectors, which is only violated by interactions. It can accommodate three flavor quasi-Dirac neutrino mixing scheme, which allows processes with violation of both lepton flavor and total lepton number symmetries. We propose a 6×6 unitary matrix for parameterizing the mixing among three flavors of quasi-Dirac neutrino. This mixing matrix is constructed by two 3×3 unitary matrices that diagonalizes the Dirac mass term in the Lagrangian. By only assuming the Standard Model V−A weak interaction, it is found that probabilities of neutrino oscillations among active flavor states and effective masses measured by single beta decay, by neutrinoless double-beta decay and by cosmology only depend on single 3×3 unitary matrix relevant to mixing of active neutrino flavors. Further, by considering 1σ and 3σ uncertainties in the measured oscillation probability of electron antineutrino from reactor, derivation of the constraint on the Majorana neutrino mass component is demonstrated. The consequence for effective Majorana neutrino mass governing the neutrinoless double-beta decay is discussed.

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Sharafiddinov, Rasulkhozha S. « Nature itself in a mirror space–time ». Canadian Journal of Physics 93, n^o 10 (octobre 2015) : 1005–8. http://dx.doi.org/10.1139/cjp-2014-0497.

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The unity of the structure of matter fields with flavor symmetry laws involves that the left-handed neutrino in the field of emission can be converted into a right-handed one and vice versa. These transitions together with classical solutions of the Dirac equation testify in favor of the unidenticality of masses, energies, and momenta of neutrinos of the different components. If we recognize such a difference in masses, energies, and momenta, accepting its ideas about that the left-handed neutrino and the right-handed antineutrino refer to long-lived leptons, and the right-handed neutrino and the left-handed antineutrino are short-lived fermions, we would follow the mathematical logic of the Dirac equation in the presence of the flavor symmetrical mass, energy, and momentum matrices. From their point of view, nature itself separates Minkowski space into left and right spaces concerning a certain middle dynamical line. Thereby, it characterizes any Dirac particle both by left and by right space–time coordinates. It is not excluded therefore that whatever the main purposes each of earlier experiments about sterile neutrinos, namely, about right-handed short-lived neutrinos may serve as the source of facts confirming the existence of a mirror Minkowski space–time.

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SINGH, N. NIMAI, et MAHADEV PATGIRI. « BIMAXIMAL MIXINGS FROM THE TEXTURE OF THE RIGHT-HANDED MAJORANA NEUTRINO MASS MATRIX ». International Journal of Modern Physics A 17, n^o 25 (10 octobre 2002) : 3629–40. http://dx.doi.org/10.1142/s0217751x02011503.

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We study the origin of neutrino masses and mixing angles which can accommodate the LMA MSW solutions of the solar neutrino anomaly as well as the solution of the atmospheric neutrino problem, within the framework of the see-saw mechanism. We employ the diagonal form of the Dirac neutrino mass matrices with the physical masses as diagonal elements in the hierarchical order. Such a choice has been motivated from the fact that the known CKM angles for the quark sector, are relatively small. We consider both possibilities where the Dirac neutrino mass matrix is either the charged lepton or the up-quark mass matrix within the framework of SO(10) GUT with or without supersymmetry. The nonzero texture of the right-handed Majorana neutrino mass matrix M R is used for the generation of the desired bimaximal mixings in a model independent way. Both hierarchical and inverted hierarchical models of the left-handed Majorana neutrino mass matrices are generated and then discussed with examples. The see-saw mass scale which is kept as a free parameter, is predicted in all the examples.

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Bu, Jian Ping, et Bei Jia. « The Constraints on the Parameters in the Decay Process μ → e γ and μ →3e at Tree Level in the Hung Model ». Advanced Materials Research 490-495 (mars 2012) : 3826–30. http://dx.doi.org/10.4028/www.scientific.net/amr.490-495.3826.

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The smallness of neutrino masses is naturally explained by the seesaw mechanism, which is usually implemented by assuming a small Dirac mass of order charged leptons’ and a large mass of sterile neutrinos of order GUT scale [1]. This makes heavy neutrinos experimentally inaccessible. If heavy neutrinos have a mass of order electroweak scale, they could be detected at high energy colliders. A model with this feature built in has been suggested recently by Hung. We analyze the constraints on the unknown parameters in the decay and .

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Sharafiddinov, Rasulkhozha S. « Vector currents of massive neutrinos of an electroweak nature ». Canadian Journal of Physics 92, n^o 10 (octobre 2014) : 1262–68. http://dx.doi.org/10.1139/cjp-2013-0458.

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The mass of an electroweakly interacting neutrino consists of the electric and weak parts responsible for the existence of its charge, charge radius, and magnetic moment. Such connections explain the formation of paraneutrinos, for example, at the polarized neutrino electroweak scattering by spinless nuclei. We derive the structural equations that relate the self-components of mass to charge, charge radius, and magnetic moment of each neutrino as a consequence of unification of fermions of a definite flavor. They indicate the availability of neutrino universality and require following its logic in a constancy law dependence of the size implied from the multiplication of a weak mass of neutrino by its electric mass. According to this principle, all Dirac neutrinos of a vector nature, regardless of the difference in their masses, have the same charge, an identical charge radius, as well as an equal magnetic moment. Thereby, the possibility appears of establishing the laboratory limits of weak masses of the investigated types of neutrinos. Finding estimates show clearly that the earlier measured properties of these particles may testify in favor of the unified mass structure of their interaction with any of the corresponding types of gauge fields.

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Aker, M., A. Beglarian, J. Behrens, A. Berlev, U. Besserer, B. Bieringer, F. Block et al. « Direct neutrino-mass measurement with sub-electronvolt sensitivity ». Nature Physics 18, n^o 2 (février 2022) : 160–66. http://dx.doi.org/10.1038/s41567-021-01463-1.

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AbstractSince the discovery of neutrino oscillations, we know that neutrinos have non-zero mass. However, the absolute neutrino-mass scale remains unknown. Here we report the upper limits on effective electron anti-neutrino mass, mν, from the second physics run of the Karlsruhe Tritium Neutrino experiment. In this experiment, mν is probed via a high-precision measurement of the tritium β-decay spectrum close to its endpoint. This method is independent of any cosmological model and does not rely on assumptions whether the neutrino is a Dirac or Majorana particle. By increasing the source activity and reducing the background with respect to the first physics campaign, we reached a sensitivity on mν of 0.7 eV c–2 at a 90% confidence level (CL). The best fit to the spectral data yields $${{\mbox{}}}{m}_{\nu }^{2}{{\mbox{}}}$$ m ν 2 = (0.26 ± 0.34) eV2 c–4, resulting in an upper limit of mν < 0.9 eV c–2 at 90% CL. By combining this result with the first neutrino-mass campaign, we find an upper limit of mν < 0.8 eV c–2 at 90% CL.

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