Observation Of Neutrino Oscillations Research Articles

Sensitivity prospects for lepton-trijet signals in the ν\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ u $$\\end{document}SMEFT at the LHeC

The observation of neutrino oscillations and masses motivates the extension of the standard model with right-handed neutrinos, leading to heavy neutrino states possibly in the electroweak scale, which could be impacted by new high-scale weakly coupled physics. A systematic tool for studying these interactions is the neutrino-extended standard model effective field theory ν\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ u $$\\end{document}SMEFT. In this work we study the prospects of the future LHeC electron-proton collider to discover or constrain the ν\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ u $$\\end{document}SMEFT interactions, performing the first dedicated and realistic analysis of the well known lepton-trijet signals, for both the lepton flavor violating pe-→μ-+3j\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$p ~ e^{-} \\rightarrow \\mu ^{-} + 3 \ extrm{j}$$\\end{document} (LFV) and the lepton number violating pe-→μ++3j\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$p ~ e^{-} \\rightarrow \\mu ^{+} + 3 \ extrm{j}$$\\end{document} (LNV) channels, for HNLs masses in the electroweak scale range: 100GeV≤mN≤500GeV\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$100 ~{\ extrm{GeV}} \\le m_N \\le 500 ~{\ extrm{GeV}}$$\\end{document}. The obtained sensitivity prospects show that the LHeC with 100fb-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$100 ~{\ extrm{fb}}^{-1}$$\\end{document} luminosity could be able to probe the scenario of a heavy N and constrain the effective couplings to a region of the parameter space as tight as the bounds that are currently considered for the O(10)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathcal {O}(10)$$\\end{document} GeV scale masses, with effective couplings of O(10-1)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathcal {O}(10^{-1})$$\\end{document} for NP scale Λ=1TeV\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Lambda =1 \\,{\ extrm{TeV}}$$\\end{document}.

Refractive neutrino masses, ultralight dark matter and cosmology

We consider in detail a possibility that the observed neutrino oscillations are due to refraction on ultralight scalar boson dark matter.We introduce the refractive mass squared, m̃2, and study its properties: dependence on neutrino energy,state of the background, etc. If the background is in a state of cold gas of particles, m̃2 shows a resonance dependence on energy. Above the resonance (E ≫ ER ), we find that m̃2 has the same properties as usual vacuum mass squared.Below the resonance, m̃2 decreases with energy, which (if realised) allows to avoid the cosmological bound on the sum of neutrino masses. Also, m̃2 may depend on time. We consider the validity of the results: effects of multiple interactions with scalars, and modification of the dispersion relation. We show that for values of parameters of the system required toreproduce the observed neutrino masses, perturbativity is broken at low energies, which border above the resonance.If the background is in the state of coherent classical field, the refractive mass does not depend on energy explicitly but may showtime dependence. It coincides with the refractive mass in a cold gas at high energies.Refractive nature of neutrino mass can be tested by searches of its dependence on energy and time.

Toward the discovery of matter creation with neutrinoless ββ decay

Observation of neutrino oscillations implies that neutrinos have mass, but one does not know whether they are described by Dirac or Majorana mass terms. The discovery of a Majorana mass would provide a test of the global symmetries of the standard model, and would have implications for the origin of the number of baryons in the Universe. To achieve this one can search for neutrinoless double-beta decay, a rare nuclear decay where two new electrons are created with no antimatter. The next generation of experiments will explore large Majorana neutrino mass values, also testing alternative theoretical models. In this review, devoted to neutrinoless double-beta decay, the particle and nuclear physics aspects involved in predicting the decay rate and the experimental search methods are discussed.

Neutrino Physics

The observation of neutrino oscillations is firm evidence of non-zero neutrino mass. Neutrino mass and mixing have been studied by neutrino oscillation experiments so far. One of the remaining questions is whether neutrinos violate CP symmetry. Exploring new CP violation is also a subject of kaon physics. There are other common physics topics between neutrino and kaon experiments. In this talk, recent progress and future prospects of neutrino experiments for topics related to kaon physics will be discussed.

Type III seesaw under A_4 modular symmetry with leptogenesis

We make an attempt to study neutrino phenomenology in the framework of type-III seesaw by considering A_4 modular symmetry in the super-symmetric context. In addition, we have included a local U(1)_{B-L} symmetry which eventually helps us to avoid certain unwanted terms in the superpotential. Hitherto, the seesaw being type-III, it involves three fermion triplet superfields Sigma _R, along with which, we have included a singlet weighton field (rho ). In here, modular symmetry plays a crucial role by avoiding the usage of excess flavon (weighton) fields. Also, the Yukawa couplings acquire modular forms which are expressed in terms of Dedekind eta function eta (tau ). However, for numerical analysis we use q expansion expressions of these couplings. Therefore, the model discussed here is triumphant enough to accommodate the observed neutrino oscillation data and also successfully explains observed baryon asymmetry of the universe through leptogenesis.

Renormalizable standard model extension with S4 symmetry for neutrino mass and mixing

We suggest a renormalizable standard model extension based on S4 symmetry that accommodates the recent observed neutrino oscillation pattern. Through the type-I seesaw mechanism, the smallness of the active neutrino mass and its hierarchy are produced. The model generates the updated data on neutrino parameters in which the reactor neutrino mixing angle θ13, the atmospheric neutrino mixing θ23, and the Dirac phase δ for both NH and IH belong to 1σ range, while the solar mixing angle θ12 = 35.70° belongs to 2σ range. The effective masses are found to be 〈 mee〉 = 5.74 meV for NH and 〈 mee〉 = 48.1 meV for IH within their allowed constraints.

Displaced neutrino jets at the LHeC

Extending the Standard Model with right-handed neutrinos (RHNs) is well motivated by the observation of neutrino oscillations. In the type-I seesaw model, the RHNs interact with the SM particles via tiny mixings with the active neutrinos, which makes their discovery in the laboratory, and in particular at collider experiments in general challenging. In this work we instead consider an extension of the seesaw model with RHNs with the addition of a leptoquark (LQ), and employ a non-minimal production mechanism of the RHN via LQ decay, which is unsuppressed by neutrino mixing. We focus on relatively light RHN with mass mathcal{O} (10) GeV and LQ with mass 1.0 TeV, and explore the discovery prospect of the RHN at the proposed Large Hadron electron Collider. In the considered mass range and with the given interaction strength, the RHN is long lived and, due to it stemming from the LQ decay, it is also heavily boosted, resulting in collimated decay products. The unique signature under investigation is thus a displaced fat jet. We use kinematic variables to separate signal from background, and demonstrate that the ratio variables with respect to energy/number of displaced and prompt tracks are useful handles in the identification of displaced decays of the RHN. We also show that employing a positron beam provides order of magnitude enhancement in the detection prospect of this signature.

Dark sector as origin of light lepton mass and its phenomenology

We discuss a model with a dark sector, in which smallness of mass for charged leptons and neutrinos can naturally be explained by one-loop effects mediated by particles in the dark sector. These new particles, including dark matter candidates, also contribute to the anomalous magnetic dipole moment, denoted by (g − 2), for charged leptons. We show that our model can explain the muon (g − 2) anomaly and observed neutrino oscillations under the constraints from lepton flavor violating decays of charged leptons. We illustrate that the scenario with scalar dark matter is highly constrained by direct searches at the LHC, while that with fermionic dark matter allows for considering dark scalars with masses of order 100 GeV. Our scenario can be tested by a precise measurement of the muon Yukawa coupling as well as the direct production of dark scalar bosons at future electron-positron colliders.

Linear seesaw model with T 7 symmetry for neutrino mass and mixing

We propose a low-scale Standard Model extension with symmetry that can successfully explain observed neutrino oscillation results within the range. Small neutrino masses are obtained via the linear seesaw mechanism. Normal and inverted neutrino mass orderings are considered with three lepton mixing angles in their experimentally allowed ranges. The model provides a suitable correlation between the solar and reactor neutrino mixing angles, which is consistent with the pattern. The prediction for the Dirac phase is for both normal and inverted orderings, including its experimentally maximum value, while those for the two Majorana phases are for normal ordering and for inverted ordering. In addition, the predictions for the effective neutrino masses are consistent with the present experimental bounds.

Origin of neutrino masses and disappearance ofprimordial antimatter

<p indent="0mm">The standard model (SM) of particle physics has proved to be a huge success in describing the microscopic structures of matter and the behaviors of strong, weak and electromagnetic forces, but it is incomplete in some aspects. For example, the SM itself provides no answer about the origin of tiny neutrino masses, and it fails in accounting for the observed matter-antimatter asymmetry of the Universe. To go beyond the SM, one may wonder whether there exists an intrinsic connection between the solutions to these two fundamental issues in particle physics and cosmology. It is argued that the seesaw mechanism for neutrino mass generation and the associated leptogenesis mechanism for cosmological baryogenesis may pave a way for our deeper understanding of the origin of neutrino masses and mysterious disappearance of primordial antimatter of the Universe. Behind these two mechanisms is the existence of heavy and sterile Majorana neutrinos, which interact with the known (light and active) neutrinos via the Yukawa interactions. The SM contains no right-handed neutrino fields, and hence there is no way to write out a Dirac neutrino mass term. The simplest way to go beyond the SM is to introduce the right-handed neutrino fields and allow for lepton number violation. In this case the right-handed neutrino fields and their charge-conjugate counterparts may constitute a Majorana mass term which, together with the Yukawa interactions between left- and right-handed neutrino fields via the Higgs field, leads us to the origin of tiny Majorana masses for three active neutrinos. Such a seesaw mechanism attributes the smallness of active neutrino masses to the largeness of sterile neutrino masses as compared with the electroweak scale. The lepton-number-violating and CP-violating decays of those heavy degrees of freedom in the early Universe may produce a net lepton-antilepton asymmetry, and the latter may be partly converted into a net baryon-antibaryon asymmetry via the sphaleron process. This is just the leptogenesis mechanism, and it has attracted a lot of attention thanks to the observations of neutrino oscillations in the past decades. The seesaw and leptogenesis scenarios are correlated with each other, and they provide an elegant way of accounting for the cosmological baryon-antibaryon asymmetry and tiny neutrino masses. A pressing question is how to test such a “killing two birds with one stone” picture at low-energy experiments. It seems that a direct test of this picture is extremely difficult or even impossible, but one may always collect various “fossils” of heavy Majorana neutrinos which might have played a crucial role in the early Universe. In this connection it will be greatly helpful to verify the Majorana nature of massive neutrinos by observing the neutrinoless double-beta decays, to measure CP violation in neutrino oscillations and to test unitarity of the 3×3 flavor mixing matrix of three active neutrinos.

Multiscalar B − L model with Σ(18) symmetry for neutrino mass and mixing

We construct a non-renormalizable [Formula: see text] model based on [Formula: see text] symmetry, whereby, neutrino mass ordering and the tiny neutrino masses are explained at tree level via type I seesaw mechanism. The model can reproduce the recent observed neutrino oscillation data in which neutrino oscillation parameters including three mixing angles [Formula: see text], Dirac CP phase plus neutrino squared-mass splittings [Formula: see text] get the best-fit values for both Normal ordering (NO) and Inverted ordering (IO). The Majorana phases are predicted to be [Formula: see text] for NO, [Formula: see text] for IO and [Formula: see text] for both NH and IO. The sum of neutrino mass and the effective neutrino mass are, respectively, predicted to be [Formula: see text] for NO while [Formula: see text] for IO and [Formula: see text] for NO while [Formula: see text] for IO which are well compatible with the most recent experimental constraints.

Multiscalar B − L extension with A4 symmetry for fermion mass and mixing with co-bimaximal scheme

We construct a multiscalar and nonrenormalizable B−L extension of the standard model with A4 group which successfully explains the recent observed neutrino oscillation pattern. The tiny neutrino masses and their orderings are reproduced via the type-I seesaw mechanism. The model predicts co-bimaximal neutrino mixing, i.e., θ23=π4, δCP=−π2 while θ13=8.57∘ for normal hierarchy and θ13=8.60∘ for inverted hierarchy. The effective neutrino masses are predicted to be 〈mee〉=10.0meV for NH and 〈mee〉=48.40meV for IH being in good agreement with the most recent experimental data. The obtained results are also in agreement with the recent experimental data on the SM quark masses, mixing angles and CP violation in the quark sector.

Multiscalar B-L extension based on S 4 flavor symmetry for neutrino masses and mixing * *This research is funded by Vietnam National Foundation for Science and Technology Development (NAFOSTED) (103.01-2017.341)

A multiscalar and nonrenormalizable extension of the standard model (SM) with symmetry which successfully explains the recently observed neutrino oscillation data is proposed. The tiny neutrino masses and their hierarchies are generated via the type-I seesaw mechanism. The model reproduces the recent experiments of neutrino mixing angles and Dirac CP violating phase in which the atmospheric angle and the reactor angle get the best-fit values while the solar angle and Dirac CP violating phase ( ) are in range of the best-fit value for the normal hierarchy (NH). For the inverted hierarchy (IH), gets the best-fit value and together with are in the range, while is in range of the best-fit value. The effective neutrino masses are predicted to be for the NH and for the IH, in good agreement with the most recent experimental data.

SMART U(1)_X: standard model with axion, right handed neutrinos, two Higgs doublets and U(1)_X gauge symmetry

To address five fundamental shortcomings of the Standard Model (SM) of particle physics and cosmology, we propose a phenomenologically viable framework based on a U(1)_X times U(1)_{PQ} extension of the SM, that we call “SMART U(1)_X”. The U(1)_X gauge symmetry is a well-known generalization of the U(1)_{B-L} symmetry and U(1)_{PQ} is the global Peccei–Quinn (PQ) symmetry. Three right handed neutrinos are added to cancel U(1)_X related anomalies, and they play a crucial role in understanding the observed neutrino oscillations and explaining the observed baryon asymmetry in the universe via leptogenesis. Implementation of PQ symmetry helps resolve the strong CP problem and also provides axion as a compelling dark matter (DM) candidate. The U(1)_X gauge symmetry enables us to implement the inflection-point inflation scenario with H_{inf} lesssim 2 times 10^{7} GeV, where H_{inf} is the value of Hubble parameter during inflation. This is crucial to overcome a potential axion domain wall problem as well as the axion isocurvature problem. The SMART U(1)_X framework can be successfully implemented in the presence of SU(5) grand unification, as we briefly show.

Entropic uncertainty relation in neutrino oscillations

Neutrino oscillation is deemed as an interesting physical phenomenon and shows the nonclassical features made apparently by the Leggett–Garg inequality. The uncertainty principle is one of the fundamental features that distinguishes the quantum world to its classical counterpart. And the principle can be depicted in terms of entropy, which forms the so-called entropic uncertainty relations (EUR). In this work, the entropic uncertainty relations that are relevant to the neutrino-flavor states are investigated by comparing the experimental observation of neutrino oscillations to predictions. From two different neutrino sources, we analyze ensembles of reactor and accelerator neutrinos for different energies, including measurements performed by the Daya Bay collaboration using detectors at 0.5 and 1.6 km from their source, and by the MINOS collaboration using a detector with a 735km distance to the neutrino source. It is found that the entropy-based uncertainty conditions strengths exhibits non-monotonic evolutions as the energy increases. We also quantify the systemic quantumness measured by quantum correlation, and derive the intrinsic relationship between quantum correlation and EUR. Furthermore, we utilize EUR as a criterion to detect entanglement of neutrino-flavor state. Our results could illustrate the potential applications of neutrino oscillations on quantum information processing in the weak-interaction processes.

Discovering leptonic forces using nonconserved currents

Differences in lepton number (i.e., $ L _e - L _\mu $, $ L _e - L _\tau $, $ L_\mu - L _\tau $, or combinations thereof) are not conserved charges in the Standard Model due to the observation of neutrino oscillations. We compute the divergence of the corresponding currents in the case of Majorana or Dirac-type neutrinos and show that, in the high energy limit, the vector interactions map onto those of a light scalar coupled to neutrinos with its coupling fixed by the observed neutrino masses and mixing. This leads to amplitudes with external light vectors that scale inversely with the vector mass. By studying these processes, we set new constraints on $ L _i - L _j $ through a combination of semi-leptonic meson decays, invisible neutrino decays, neutrinoless double beta decays, and observations of Big Bang Nucleosynthesis/supernova, which can be much stronger than previous limits for vector masses below an eV. These bounds have important implications on the experimental prospects of detecting $ L _i - L _j $ long-range forces.

Quantification of quantumness in neutrino oscillations

Neutrino oscillation is an important physical phenomenon in elementary particle physics, and its nonclassical features can be revealed by the Leggett–Garg inequality. It shows that its quantum coherence can be sustained over astrophysical length scales. In this work, we investigate the measure of quantumness in experimentally observed neutrino oscillations via the nonlocal advantage of quantum coherence (NAQC), quantum steering, and Bell nonlocality. From various neutrino sources, ensembles of reactor and accelerator neutrinos are analyzed at distinct energies, such as Daya Bay (0.5 km and 1.6 km) and MINOS (735 km) collaborations. The NAQC of two-flavor neutrino oscillation is characterized experimentally compared to the theoretical prediction. It exhibits non-monotonously evolutive phenomenon with the increase of energy. Furthermore, it is found that the NAQC is a stronger quantum correlation than quantum steering and Bell nonlocality even in the order of km. Hence, for an arbitrary bipartite neutrino-flavor state with achieving a NAQC, it must be also a steerable and Bell nonlocal state. The results might offer an insight into the neutrino oscillation for the further applications on quantum information processing.

Long-lived TeV-scale right-handed neutrino production at the LHC in gauged U(1)X model

A gauged U(1)X extension of the Standard Model is a simple and consistent framework to naturally incorporate three right-handed neutrinos (RHNs) for generating the observed light neutrino masses and mixing by the type-I seesaw mechanism. We examine the collider testability of the U(1)X model, both in its minimal form with the conventional charges, as well as with an alternative charge assignment, via the resonant production of the U(1)X gauge boson (Z′) and its subsequent decay into a pair of RHNs. We first derive an updated upper limit on the new gauge coupling gX as a function of the Z′-boson mass from the latest LHC dilepton searches. Then we identify the maximum possible cross section for the RHN pair-production under these constraints. Finally, we investigate the possibility of having one of the RHNs long-lived, even for a TeV-scale mass. Employing the general parametrization for the light neutrino mass matrix to reproduce the observed neutrino oscillation data, we perform a parameter scan and find a simple formula for the maximum RHN lifetime as a function of the lightest neutrino mass eigenvalue (mlightest). We find that for mlightest≲10−5 eV, one of the RHNs in the minimal U(1)X scenario can be long-lived with a displaced-vertex signature which can be searched for at the LHC and/or with a dedicated long-lived particle detector, such as MATHUSLA. In other words, once a long-lived RHN is observed, we can set an upper bound on the lightest neutrino mass in this model.

ν’s in Particle Physics and Cosmology

We propose a minimal scale-invariant (SI) scotogenic model and study its phenomenological implications. The SI scotogenic predicts a singlet scalar (dilaton) that triggers electroweak symmetry breaking and sources the lepton number violation that allows radiative neutrino mass. A viable parameter space is found for dark matter candidate and the observed neutrino oscillation. The model can be probed in lepton flavor violating processes, future dark matter direct detection experiments, and collider searches.

Quantifying quantum coherence in experimentally observed neutrino oscillations

Neutrino oscillation represents an intriguing physical phenomenon where the quantumness can be maintained and detected over a long distance. Previously, the non-classical character of neutrino oscillation was tested with the Leggett-Garg inequality, where a clear violation of the classical bound was observed [J. A. Formaggio et al., Phys. Rev. Lett. 117, 050402 (2016)]. However, there are several limitations in testing neutrino oscillations with the Leggett-Garg inequality. In particular, the degree of violation of the Leggett-Garg inequality cannot be taken as a "measure of quantumness". Here we focus on quantifying the quantumness of experimentally-observed neutrino oscillation, using the tools of recently-developed quantum resource theory. We analyzed ensembles of reactor and accelerator neutrinos at distinct energies from a variety of neutrino sources, including Daya Bay (0.5 km and 1.6 km), Kamland (180 km), MINOS (735 km), and T2K (295 km). The quantumness of the three-flavoured neutrino oscillation is characterized within a 3{\sigma} range relative to the theoretical prediction. It is found that the maximal coherence was observed in the neutrino source from the Kamland reactor. However, even though the survival probability of the Daya Bay experiment did not vary significantly (dropped about 10 percent), the coherence recorded can reach up to 40 percent of the maximal value. These results represent the longest distance over which quantumness were experimentally determined for quantum particles other than photons.