Flavor-changing Neutrino Research Articles

Comprehensive Analysis of the Neutrino Process in Core-collapsing Supernovae

We investigate the neutrino flavor change effects due to neutrino self-interaction and shock wave propagation, as well as the matter effects on the neutrino process in core-collapsing supernovae (CCSNe). For the hydrodynamics, we use two models: a simple thermal bomb model and a specified hydrodynamics model for SN1987A. For the presupernova model, we take an updated model, adjusted to explain SN1987A, which employs recent developments in the (n, γ) reaction rates for nuclei near the stability line (A ∼ 100). As for the neutrino luminosity, we adopt two different models: equivalent neutrino luminosity and nonequivalent luminosity models. The latter is taken from a synthetic analysis of CCSN simulation data, which quantitatively presented the results obtained by various neutrino transport models. Relevant neutrino-induced reaction rates are calculated using a shell model for light nuclei and a quasiparticle random phase approximation model for heavy nuclei. For each model, we present abundances of the light nuclei (7Li, 7Be, 11B, and 11C) and the heavy nuclei (92Nb, 98Tc, 138La, and 180Ta) produced by the neutrino process. The light nuclei abundances turn out to be sensitive to the Mikheyev–Smirnov–Wolfenstein (MSW) region around O-Ne-Mg layer while the heavy nuclei are mainly produced prior to the MSW region. Through detailed analyses, we find that neutrino self-interaction becomes a key ingredient, in addition to the MSW effect, for understanding the neutrino process and the relevant nuclear abundances. The normal mass hierarchy is shown to be more compatible with the meteorite data. The main nuclear reactions for each nucleus are also investigated in detail.

Flavor-changing Majoron interactions with leptons

When the Standard Model Higgs sector is extended with a complex singlet that breaks global lepton number symmetry spontaneously, a massless Goldstone boson called the Majoron J arises. In addition to increasing Higgs invisible decay through mixing, the Majoron can generally have flavor-changing interactions with fermions. We find that type-III seesaw model poses such interesting properties with both charged leptons and neutrinos. This opens up new channels to search for the Majoron. We use the experimental data such as muonium-anti-muonium oscillation and flavor-changing neutrino and charged lepton decays to put constraints on the couplings. As a novel way to reveal the chiral properties of these interactions, we propose an experimentally measurable polarization asymmetry of flavor-changing l to l' J decays.

Challenge to anomalous phenomena in solar neutrino

We suggest a would-be solution to the solar neutrino tension why solar neutrinos appear to mix differently from reactor antineutrinos, in theoretical respect. To do that, based on an extended theory with light sterile neutrinos added we derive a general transition probability of neutrinos born with one flavor tuning into a different flavor. Three new mass-squared differences are augmented in the extended theory: Delta {m}_{mathrm{ABL}}^2lesssim mathcal{O}left({10}^{-11}right) eV2 optimized at astronomical-scale baseline (ABL) oscillation experiments and one Delta {m}_{mathrm{SBL}}^2lesssim mathcal{O}(1) eV2 optimized at reactor short-baseline (SBL) oscillation experiments. With a so-called composite matter effect that causes a neutrino flavor change via the effects of sinusoidal oscillation including the Mikheyev-Smirnov-Wolfenstein matter effect, we find that the value of ∆m2 measured from reactor antineutrino experiments can be fitted with that from the 8B solar neutrino experiments for roughly Delta {m}_1^2lesssim {10}^{-13} eV2 and Delta {m}_2^2simeq mathcal{O}left({10}^{-11}right) eV2. Nonetheless, we find that the current data (solar neutrino alone) is not precise enough to test the proposed scenario. Future precise measurements of 8B and pep solar neutrinos may confirm and/or improve the value of Delta {m}_2^2 .

Lepton flavor violation and neutrino masses from A5 and CP in the non-universal MSSM

We analyze the phenomenological consequences of embedding a flavor symmetry based on the groups A5 and CP in a supersymmetric framework. We concentrate on the leptonic sector, where two different residual symmetries are assumed to be conserved at leading order for charged and neutral leptons. All possible realizations to generate neutrino masses at tree level are investigated. Sizable flavor violating effects in the charged lepton sector are unavoidable due to the non-universality of soft-breaking terms determined by the symmetry. We derive testable predictions for the neutrino spectrum, lepton mixing and flavor changing processes with non-trivial relations among observables.

Neutrino Oscillation Processes with a Change of Lepton Flavor in Quantum Field-Theoretical Approach

The oscillating probabilities of lepton flavor changing neutrino oscillation processes, where neutrinos are detected by weak charged-current and neutral-current interactions, are calculated in a quantum field-theoretical approach to neutrino oscillations based on a modification of the Feynman propagator in the momentum representation. The approach is most similar to the standard Feynman diagram technique in the momentum representation. It is found that the oscillating distance-dependent probabilities of detecting an electron in experiments with neutrino production in the muonic decay of π+-meson and the detection of the produced neutrino by charged-current and neutral-current interactions exactly coincide with the corresponding probabilities calculated in the standard approach.

Neutrino masses in a two Higgs doublet model with a U(1) gauge symmetry

General Two Higgs Doublet Models (2HDM) are popular Standard Model extensions but feature flavor changing interactions and lack neutrino masses. We discuss a 2HDM where neutrino masses are generated via type I seesaw and propose an extension where neutrino masses are generated via a type II seesaw mechanism with flavor changing interactions being absent via the presence of a U(1) gauge symmetry. After considering a variety of bounds such as those rising from collider and electroweak precision we show that our proposal stands as a UV complete 2HDM with a dark photon where neutrino masses and flavor changing interactions are addressed. A possible dark matter realization is also discussed.

Mass stability in classical Stueckelberg-Horwitz-Piron electrodynamics

It is well-known that the 5D gauge structure of Stueckelberg-Horwitz-Piron (SHP) electrodynamics permits the exchange of mass between particles and the electromagnetic fields induced by their motion, even at the classical level. This phenomenon presents two closely related problems: (1) Under what circumstances can real particles evolve sufficiently off-shell to account for mass changing phenomena such as flavor-changing neutrino interactions and low energy nuclear reactions? (2) What accounts for the stability of the measured masses of the known particles? To approach these questions, we first propose a toy model in which a particle evolving through a complex charged environment can acquire a significant mass shift for a short time. We then consider a classical self-interaction that tends to restore on-shell propagation.

The Sudbury Neutrino Observatory: Observation of Flavor Change for Solar Neutrinos

The Sudbury Neutrino Observatory (SNO) experiment was constructed by an international scientific collaboration primarily to provide a clear determination of whether solar neutrinos change their flavor in transit from the core of the sun to the earth. The detector used 1000 tonnes of heavy water (>99.92% D2O) in an ultra-clean location 2 km underground in INCO's Creighton mine near Sudbury, Canada to observe two separate reactions of neutrinos on deuterium. The first reaction was sensitive only to electron flavor neutrinos and the second reaction was equally sensitive to all neutrino flavors. The measurements by SNO showed clearly that the hypothesis of no neutrino flavor change was ruled out by more than 5.3 standard deviations. The observation of flavor change for neutrinos implies that they have a non-zero mass. The measured total flux of active neutrinos from 8B decay in the sun was found to be in excellent agreement with the predictions of solar model calculations. This paper describes the history and scientific measurements of the SNO experiment.2

The Sudbury Neutrino Observatory: Observation of flavor change for solar neutrinos

The Sudbury Neutrino Observatory (SNO) experiment was constructed by an international scientific collaboration primarily to provide a clear determination of whether solar neutrinos change their flavor in transit from the core of the sun to the earth. The detector used 1000 tonnes of heavy water (>99.92% D2O) in an ultra‐clean location 2 km underground in INCO's Creighton mine near Sudbury, Canada to observe two separate reactions of neutrinos on deuterium. The first reaction was sensitive only to electron flavor neutrinos and the second reaction was equally sensitive to all neutrino flavors. The measurements by SNO showed clearly that the hypothesis of no neutrino flavor change was ruled out by more than 5.3 standard deviations. The observation of flavor change for neutrinos implies that they have a non‐zero mass. The measured total flux of active neutrinos from 8B decay in the sun was found to be in excellent agreement with the predictions of solar model calculations. This paper describes the history and scientific measurements of the SNO experiment.

Non-unitary neutrino propagation from neutrino decay

Neutrino propagation in space–time is not constrained to be unitary if very light states – lighter than the active neutrinos – exist into which neutrinos may decay. If this is the case, neutrino flavor-change is governed by a handful of extra mixing and “oscillation” parameters, including new sources of CP-invariance violation. We compute the transition probabilities in the two- and three-flavor scenarios and discuss the different phenomenological consequences of the new physics. These are qualitatively different from other sources of unitarity violation discussed in the literature.

Analysis of neutrino mass, mixing and flavor change

Established results on neutrino mass, mixing and flavor change (as of 2009) are briefly reviewed. Status and prospects of unknown neutrino properties (smallest mixing angle, Dirac/Majorana nature, absolute masses and their hierarchy) are also discussed.

Physical range of majorana neutrino mixing parameters

If neutrinos are Majorana fermions, the lepton mixing parameter space consists of six mixing parameters: three mixing angles and three CP-odd phases. A related issue concerns the physical range of the mixing parameters. What values should these take so that all physically distinguishable mixing scenarios are realized? We present a detailed discussion of the lepton mixing parameter space in the case of two and three active neutrinos and in the case of three active and N sterile neutrinos. We emphasize that this question, which has been a source of confusion even among neutrino physicists, is connected to an unambiguous definition of the neutrino mass eigenstates. We find that all Majorana phases can always be constrained to lie between 0 and {pi}, and that all mixing angles can be chosen positive and at most less than or equal to {pi}/2 provided the Dirac phases are allowed to vary between -{pi} and {pi}. We illustrate our results with several examples. Finally, we point out that, in the case of new flavor-changing neutrino interactions, the lepton mixing parameter space may need to be enlarged. We properly qualify this statement, and offer concrete examples.

Detection of ultra high-energy tau-neutrinos with fluorescence detectors

We calculate the possible number of Extensive Air Showers originated by tau neutrinos in Fluorescence Detectors like the ones of the Pierre Auger Observatory. We consider models of production of electron and muon neutrinos in extra galactic objects and Topological Defects, as well as the possibility of neutrino flavor change in the propagation of the neutrinos between the source and the Earth. The neutrino cross section was calculated by the extrapolation of the standard model parton distribution functions until energies of the order of 10 21 eV. However, due to uncertainties in the extrapolation for energies higher than 10 12 eV the results are not robust. We conclude that, depending on the relation between flux and cross section, there is a strict range of energy for the tau neutrinos to generate double extensive air showers detectable in Fluorescence Detectors. The tau neutrino energy must be approximately 10 18 eV and the event rate can vary some orders of magnitude around one event per year, depending on the flux-cross section relation and detector characteristics.

Results from Solar and Reactor Neutrino Experiments

The evidence for neutrino flavour change and for the LMA solution for the neutrino mixing parameters is briefly summarized. Recent results and current research from SNO and SK are then described along with the potential for KamLAND, Borexino and planned new experiments to extend our knowledge by studying low energy solar neutrinos. The sensitivity of reactor experiments in determining θ 13 is discussed and the detection technique and principal backgrounds are explained. Finally the status of proposed and funded reactor θ 13 experiments is presented.

Simon Peter Rosen

Simon Peter Rosen

Stellar collapse dynamics with neutrino flavor changing neutral currents

We perform one-zone simulations of the infall epoch of a presupernova stellar core in the presence of neutrino flavor changing scattering interactions. Our calculations give a self-consistent assessment of the relationship between flavor changing rates and the reduction in electron fraction and redistribution of initial electron lepton number among the neutrino flavors. We discuss and include in our calculations subnuclear density medium corrections for flavor changing scattering coherence factors. We find that flavor changing couplings {epsilon}>3x10{sup -4} in either the {nu}{sub e}{r_reversible}{nu}{sub {mu}} or {nu}{sub e}{r_reversible}{nu}{sub {tau}} channels result in a dynamically significant reduction in the core electron fraction relatively soon after neutrino trapping and well before the core reaches nuclear matter density.

Solar neutrinos, SNO and SNOLAB

The Sudbury Neutrino Observatory is a 1000 tonne heavy water Cherenkov detector situated 2 km underground in INCO's Creighton mine near Sudbury, Ontario, Canada. In the first two phases of the project reported to date, the charged current reaction on deuterium has been used to measure the flux and energy spectrum of solar electron neutrinos and the neutral current reaction has been used to measure the total flux of active neutrinos. Clear evidence of neutrino flavour change has been observed and the total active flux is found to be in agreement with solar model calculations. The experimental third phase with an array of neutron detectors is in progress. The expansion of the underground laboratory to create an international facility known as SNOLAB will be completed in 2007. A number of international experiments for the future detection of lower energy solar neutrinos, geo-neutrinos, dark matter and double beta decay are described.

Flavor changing supersymmetry interactions in a supernova

We consider for the first time flavor changing neutral currents (FCNC’s) in the infall stage of stellar collapse. We take as an example R-Parity violating interactions of the minimal standard supersymmetric model involving neutrinos and quarks. However, our considerations extend to other kinds of flavor changing neutrino reactions as well. We examine non-forward neutrino scattering processes on heavy nuclei and free nucleons in the supernova core. This investigation has led to four principal original discoveries/products: (1) first calculation of neutrino flavor changing cross sections for spin 1/2 (e.g., free nucleon) and spin 0 nuclear targets; (2) discovery of nuclear mass number squared ( A 2) coherent amplification of neutrino-quark FCNC’s; (3) analysis of FCNC-induced alteration of electron capture and weak/nuclear equilibrium in the collapsing core; and (4) generalization of the calculated cross sections (mentioned in 1) for the case of hot heavy nuclei to be used in collapse/supernova and neutrino transport simulations. The scattering processes that we consider allow electron neutrinos to change flavor during core collapse, thereby opening holes in the ν e sea, which allows electron capture to proceed and results in a lower core electron fraction Y e. A lower Y e implies a lower homologous core mass, a lower shock energy, and a greater nuclear photo-disintegration burden for the shock. In addition, unlike the standard supernova model, the core now could have net muon and/or tau lepton numbers. These effects could be significant even for supersymmetric couplings below current experimental bounds.

The Sudbury Neutrino Observatory

The Sudbury Neutrino Observatory (SNO) is a one kiloton heavy water Cherenkov detector sensitive to the flavor content of the 8 B neutrinos from the sun. Results from the first two phases of SNO, the pure D 2 O phase and the salt phase, show evidence for neutrino flavor change as the solution to the solar neutrino problem. SNO is now entering its third phase of operation in which 3 He proportional counters have been deployed inside the D 2 O.

Neutrino Properties from Measurements using Astrophysical and Terrestrial Sources

AbstractThe current knowledge of neutrino properties has been derived from measurements performed with both astrophysical and terrestrial sources. Observations of neutrino flavor change have been made with neutrinos generated in the solar core, through cosmic ray interactions in the atmosphere and in nuclear reactors. A summary is presented of the current knowledge of neutrino properties and a description is provided for future measurements that could provide more complete information on neutrino properties.