Neutrino Fields Research Articles

Perturbing fast neutrino flavor conversion

The flavor evolution of neutrinos in dense astrophysical sources, such as core-collapse supernovae or compact binary mergers, is non-linear due to the coherent forward scattering of neutrinos among themselves. Recent work in this context has been addressed to figure out whether flavor equipartition could be a generic flavor outcome of fast flavor conversion. We investigate the flavor conversion physics injecting random perturbations in the neutrino field in two simulation setups: 1. a spherically symmetric simulation shell without periodic boundaries, with angular distributions evolving dynamically thanks to non-forward scatterings of neutrinos with the background medium, and neutrino advection; 2. a periodic simulation shell, with angular distributions of neutrinos defined a priori and neutrino advection. We find that, independent of the exact initial flavor configuration and type of perturbations, flavor equipartition is generally achieved in the system with periodic boundaries; in this case, perturbations aid the diffusion of flavor structures to smaller and smaller scales. However, flavor equipartition is not a general outcome in the simulation shell without periodic boundaries, where the inhomogeneities induced perturbing the neutrino field affect the flavor evolution, but do not facilitate the diffusion of flavor waves. This work highlights the importance of the choice of the simulation boundary conditions in the exploration of fast flavor conversion physics.

Renormalization of a Standard Model extension with a Dark Abelian Sector and predictions for the W-boson mass

The described Dark Abelian Sector Model (DASM) extends the Standard Model (SM) by a “dark” sector containing a spontaneously broken U(1)d gauge group. Keeping this dark sector quite generic we only add one additional Higgs boson, one Dirac fermion, and right-handed SM-like neutrinos to the SM. Using the only two singlet operators of the SM with dimension less than 4 (the U(1)Y field-strength tensor and the SM Higgs mass operator |Φ|2) as well as the right-handed neutrino fields we open up three portals to the dark sector. Dark sectors, such as the one of the DASM, that introduce an additional Higgs boson H as well as an additional Z′ gauge boson can have a large influence on the predictions for electroweak precision observables and even accommodate possible dark matter candidates. We consider one of the two Higgs bosons to be the known 125 GeV Higgs boson and parameterize the extension of the scalar sector by the mass of the second Higgs boson, the Higgs mixing angle, and a Higgs self-coupling. We do not assume any mass hierarchy in the gauge sector and use the mass of the additional Z′ boson and a corresponding gauge-boson mixing angle to parameterize the extension of the gauge sector. The fermion sector is parameterized by the mass of the additional fermion and a fermion mixing angle. We describe an on-shell as well as an MS¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\overline{\ extrm{MS}} $$\\end{document} renormalization scheme for the DASM sectors and give explicit results for the renormalization constants at the 1-loop level, and, thus, prepare the ground for full NLO predictions for collider observables in the DASM. As a first example, we provide the DASM prediction for the W-boson mass derived from muon decay.

Neutrino fast flavor instability in three dimensions for a neutron star merger

The flavor evolution of neutrinos in core collapse supernovae and neutron star mergers is a critically important unsolved problem in astrophysics. Following the electron flavor evolution of the neutrino system is essential for calculating the thermodynamics of compact objects as well as the chemical elements they produce. Accurately accounting for flavor transformation in these environments is challenging for a number of reasons, including the large number of neutrinos involved, the small spatial scale of the oscillation, and the nonlinearity of the system. We take a step in addressing these issues by presenting a method which describes the neutrino fields in terms of angular moments. We apply our moment method to neutron star merger conditions and show it simulates fast flavor neutrino transformation in a region where this phenomenon is expected to occur. By comparing with particle-in-cell calculations we show that the moment method is able to capture the three phases of growth, saturation, and decoherence, and correctly predicts the lengthscale of the fastest growing fluctuations in the neutrino field.

Axion–neutrino couplings, late-time phase transitions and the far infrared physics

The far infrared physics is a fascinating topic for theoretical physics, since the foundation of quantum field theory and neutrinos seem to be strongly related with the far infrared physics of our Universe. In this work we shall explore the possibility of a late-time thermal phase transition caused by the axion–neutrino interactions. The axion is assumed to be the misalignment axion which is coupled primordially to a chiral symmetric neutrino. The chiral symmetry is supposed to be broken either spontaneously or explicitly, and two distinct phenomenological models of axion–neutrinos are constructed. The axion behaves as cold dark matter during all its evolution eras, however if we assume that the axion and the neutrino fields interact coherently in a classical way as fields, or as ensembles, then we consider thermal effects in the axion sector, due to the values of operators ϕ for the axion and ν̄ν due to the neutrinos. The thermal equilibrium between the two has no effect to the axion effective potential for a wide temperature range. As we show, contrary to the existing literature, the axion never becomes destabilized due to the finite temperature effects, however if axion-Higgs higher order non-renormalizable operators are present in the Lagrangian, the axion potential is destabilized in the temperature range T∼0.1MeV down to T∼0.01eV and a first order phase transition takes place. The initial axion vacuum decays to the energetically more favorable axion vacuum, and the latter decays to the Higgs vacuum which is more preferable. This late-time phase transition might take place in the redshift range z∼385−37 and thus it may cause density fluctuations in the post-recombination era. This might be the source of large scale matter structure at high redshifts z≥9. Following the literature, we qualitatively discuss the implications of such a late-time phase transition at the astrophysical and cosmological level.

CP violation in light neutrino oscillations and heavy neutrino decays: A general and explicit seesaw-bridged correlation

With the help of a block parametrization of the canonical seesaw flavor textures in terms of the Euler-like rotation angles and CP-violating phases, we derive a general and explicit expression for the Jarlskog invariant of CP violation in neutrino oscillations and compare it with the CP-violating asymmetries of heavy Majorana neutrino decays within the minimal seesaw framework which contains two right-handed neutrino fields. Two simplified scenarios are discussed to illustrate how direct or indirect the correlation between these two types of CP violation can be.

Neutrino mass and leptogenesis in a hybrid seesaw model with a spontaneously broken CP

We introduce a novel hybrid framework combining type I and type II seesaw models for neutrino mass where a complex vacuum expectation value of a singlet scalar field breaks CP spontaneously. Using pragmatic organizing symmetries we demonstrate that such a model can simultaneously explain the neutrino oscillation data and generate observed baryon asymmetry through leptogenesis. Interestingly, natural choice of parameters leads to a mixed leptogenesis scenario driven by nearly degenerate scalar triplet and right handed singlet neutrino fields for which we present a detailed quantitative analysis.

Do we have enough evidence to invalidate the mean-field approximation adopted to model collective neutrino oscillations?

The recent body of work points out that the mean-field approximation, widely employed to mimic the neutrino field within a neutrino-dense source, might give different results in terms of flavor evolution with respect to the correspondent many-body treatment. In this paper, we investigate whether such conclusions derived within a constrained framework should hold in an astrophysical context. We show that the plane waves, commonly adopted in the many-body literature to model the neutrino field, provide results that are crucially different with respect to the ones obtained using wave packets of finite size streaming with a nonzero velocity. The many-body approach intrinsically includes coherent and incoherent scatterings. The mean-field approximation, on the other hand, only takes into account the coherent scattering in the absence of the collision term. Even if incoherent scatterings are included in the mean-field approach, the nature of the collision term is different from that in the many-body approach. Because of this, if only a finite number of neutrinos is considered, as often assumed, the two approaches naturally lead to different flavor outcomes. These differences are further exacerbated by vacuum mixing. We conclude that existing many-body literature, based on closed neutrino systems with a finite number of particles, is neither able to rule out nor assess the validity of the mean-field approach adopted to simulate the evolution of the neutrino field in dense astrophysical sources, which are open systems.

Dark matter and neutrino masses in a Portalino-like model

We explore a Portalino-like model of dark matter and neutrino masses in which right-handed neutrino fields connect gauge neutral operators from the Standard Model and Hidden Sector. Neutrino masses are generated via a seesaw-like mechanism that can explain the light active neutrino masses. The model includes a “Portalino” state that connects the two sectors via the neutrino portal. Dark Matter in this model consists of a hidden sector Dirac fermion that dominantly freezes-out via resonant annihilations into other hidden sector states, which ultimately results in a population of Portalinos. Due to small mixing in the extended neutrino sector these Portalinos tend to be cosmologically long lived, decaying into Standard Model particles leading to constraints on the model from Big Bang Nucleosynthesis and measurements of the Cosmic Microwave Background radiation. Combining these limits with direct constraints on the size of the Portalino–neutrino mixing and the assumptions of the model the viable mass ranges for the Portalino states are found to be {0.02}~hbox {eV}lesssim m_n lesssim {6.4}~hbox {eV} or {489}~{hbox {MeV}} lesssim m_n lesssim TeV. Indirect dark matter signals in the form of highly boosted, mono-energetic Portalinos produced in Dark Matter annihilations provide a target for neutrino telescopes.

Right-handed Dirac and Majorana neutrinos at Belle II

We assess the ability of the Belle II experiment to probe the Dirac or Majorana nature of a massive right-handed neutrino (RHN) N in the MeV to GeV mass range. We consider the production and decay of RHNs to proceed via new interactions described by the standard model effective field theory (SMEFT) extended with right-handed neutrino fields (SMNEFT), and not via mass mixing with active neutrinos. We find that Belle II has the potential to discover N if kinematically accessible. We perform detailed simulations of the angular distributions of lepton pairs from the decay of N produced in two-body and three-body decays of B mesons. We show that for mN above 100 MeV, Belle II can distinguish between Dirac and Majorana neutrinos at more than the 5σ CL for most operators, and the combination of the production and decay operators can be identified from the subsequent decay of the heavy neutrino. Also, the production operators can be identified using three-body B meson decay for any mN if the B → DℓN and B → D*ℓN events can be well separated.

Effect of minimal length uncertainty on neutrino oscillation

Abstract In this paper, we study the effect of the minimal length on neutrino oscillation in a static magnetic field. In the framework of the generalized uncertainty principle, we reformulate the Hamiltonian for a relativistic neutrino moving in a magnetic field oriented along the z-direction of Cartesian coordinates. Using the modified energy spectrum, we obtain the oscillation probability for different neutrino flavors. In addition, we obtain the energy differences for the neutrino-mass eigenstates. We find that the energy and energy difference depend on the minimal length parameter α, and the energy difference becomes independent of α when the magnetic field is not present. In addition, we find that the modified probability of oscillation differs from the usual probability of oscillation if a magnetic field is present. Using the current experimental result, we estimate the upper bound on the deformation parameter and the minimal length, and find that the upper bound on the minimal length scale is less than the electroweak scale. If the minimal length is at Planck scale, the minimal length formalism leads to the same result as a quantum theory of gravity with an S U 2 L ⊗ U 1 $SU{\left(2\right)}_{L}\otimes U\left(1\right)$ effective invariant dimension-5 Lagrangian including neutrino and Higgs fields.

Hollow vortices of neutrino from Kerr black hole

In the present paper, a novel family of neutrino fields with a hollow distribution outside a rotating black hole is developed. To analyze the hollow neutrino field which excited from the Kerr black hole a theoretical method is proposed. The neutrinos wave function from the Kerr black hole is reported as hypergeometric form. Similar to the hollow in the core of the rotating black hole, the emitted neutrinos with a dark core are reported. The emitted neutrino beams are characterized by a tube of energy and angular momentum with a singularity at the center. The tubes have a symmetric axis that coincided with the symmetric axis of the rotating black hole. The number rate, emitted power, and angular momentum of the neutrinos near the rotation axis of the black hole vanish. Furthermore, the maximum rate is taken place near the equator plane of the black hole. As the black hole is rotating, its angular momentum is transferred to the emitted neutrinos, hence the helicity of the neutrinos wave function is excited.

Visible neutrino decays and the impact of the daughter-neutrino mass

We compute the differential decay width of two- and three-body neutrino decays, assuming neutrinos are Dirac fermions and allowing for the possibility that the decay-daughters have nonzero masses. We examine different hypotheses for the interaction that mediates neutrino decay and concentrate on identifying circumstances where the decay-daughters can significantly impact the neutrino-decay signature at different experiments. We are especially interested in decay daughters produced by right-chiral neutrino fields, when the mass of the daughter plays a decisive role. As a concrete example, we compare the effects of visible and invisible antineutrino decays at the JUNO experimental setup.

Neutrino flavor mixing with moments

The successful transition from core-collapse supernova simulations using classical neutrino transport to simulations using quantum neutrino transport will require the development of methods for calculating neutrino flavor transformations that mitigate the computational expense. One potential approach is the use of angular moments of the neutrino field, which has the added appeal that there already exist simulation codes which make use of moments for classical neutrino transport. Evolution equations for quantum moments based on the quantum kinetic equations can be straightforwardly generalized from the evolution of classical moments based on the Boltzmann equation. We present an efficient implementation of neutrino transformation using quantum angular moments in the free streaming, spherically symmetric bulb model. We compare the results against analytic solutions and the results from more exact multiangle neutrino flavor evolution calculations. We find that our moment-based methods employing scalar closures predict, with good accuracy, the onset of collective flavor transformations seen in the multiangle results. However in some situations they overestimate the coherence of neutrinos traveling along different trajectories. More sophisticated quantum closures may improve the agreement between the inexpensive moment-based methods and the multiangle approach.

Destroying general family of rotating and accelerating charged Plebanski–Demianski black holes

Neglecting the self-energy, self-force and radiative effects, we apply Wald’s Gedanken experiment to destroy the general family of rotating and accelerating charged Plebanski–Demianski (PD) black hole (BH) by capturing a test-charged particle. We investigate that an extremal or a near-extremal PD BH can turn into a naked singularity by capturing the test particle. We also discuss the overspinning of PD BHs with a neutral test scalar field. Furthermore, we discuss the destruction of the near-extremal PD BH with the neutrino fields.

Identifying a minimal flavor symmetry of the seesaw mechanism behind neutrino oscillations

In the canonical seesaw framework flavor mixing and CP violation in weak charged-current interactions of light and heavy Majorana neutrinos are correlated with each other and described respectively by the 3 × 3 matrices U and R. We show that the very possibility of |Uμi| = |Uτi| (for i = 1, 2, 3), which is strongly indicated by current neutrino oscillation data, automatically leads to a novel prediction |Rμi| = |Rτi| (for i = 1, 2, 3). We prove that behind these two sets of equalities and the experimental evidence for leptonic CP violation lies a minimal flavor symmetry — the overall neutrino mass term keeps invariant when the left-handed neutrino fields transform as νeL→ (νeL)c, νμL→ (ντL)c, ντL→ (νμL)c and the right-handed neutrino fields undergo an arbitrary unitary CP transformation. Such a generalized μ-τ reflection symmetry may help constrain the flavor textures of active and sterile neutrinos to some extent in the seesaw mechanism.

Unruh Effect for Mixed Neutrinos and the KMS Condition

The quantization of mixed (neutrino) fields in an accelerated background reveals a non-thermal nature for Unruh radiation, which can be fitted by a Tsallis-like distribution function. However, for relativistic flavor neutrinos, which are represented by the standard Pontecorvo states, such a correction turns out to be negligible and thermality is restored. We show that the usage of Pontecorvo states for the calculation of the decay rate of an accelerated proton in the laboratory and comoving frames leads to consistent results and correctly implements the KMS thermal condition. Thus, the employment of these states in the above framework is not at odds with the principle of general covariance, in contrast to recent claims in the literature.

Visible energy and angular distributions of the charged particle from the τ −decay in bto ctau left(mu {overline{nu}}_{mu }{nu}_{tau },{pi nu}_{tau },{rho nu}_{tau}right){overline{nu}}_{tau } reactions

We study the d2Γd/(dωd cos θd), dΓd/d cos θd and dΓd/dEd distributions, which are defined in terms of the visible energy and polar angle of the charged particle from the τ −decay in bto ctau left(mu {overline{nu}}_{mu }{nu}_{tau },{pi nu}_{tau },{rho nu}_{tau}right){overline{nu}}_{tau } reactions. These differential decay widths could be measured in the near future with certain precision. The first two contain information on the transverse tau-spin, tau-angular and tau-angular-spin asymmetries of the {H}_bto {H}_ctau {overline{nu}}_{tau } parent decay and, from a dynamical point of view, they are richer than the commonly used one, d2Γd/(dωdEd), since the latter only depends on the tau longitudinal polarization. We pay attention to the deviations with respect to the predictions of the standard model (SM) for these new observables, considering new physics (NP) operators constructed using both right- and left-handed neutrino fields, within an effective field-theory approach. We present results for {Lambda}_bto {Lambda}_ctau left(mu {overline{nu}}_{mu }{nu}_{tau },{pi nu}_{tau },{rho nu}_{tau}right){overline{nu}}_{tau } and overline{B}to {D}^{left(ast right)}tau left(mu {overline{nu}}_{mu }{nu}_{tau },{pi nu}_{tau },{rho nu}_{tau}right){overline{nu}}_{tau } sequential decays and discuss their use to disentangle between different NP models. In this respect, we show that dΓd/d cos θd, which should be measured with sufficiently good statistics, becomes quite useful, especially in the τ → πντ mode. The study carried out in this work could be of special relevance due to the recent LHCb measurement of the lepton flavor universality ratio {mathrm{mathcal{R}}}_{Lambda_c} in agreement with the SM. The experiment identified the τ using its hadron decay into π−π+π−ντ, and this result for {mathrm{mathcal{R}}}_{Lambda_c} , which is in conflict with the phenomenology from the b-meson sector, needs confirmation from other tau reconstruction channels.

NuSQuIDS: A toolbox for neutrino propagation

The Neutrino Simple Quantum Integro-Differential Solver (nuSQuIDS) is a C++ code based on SQuIDS that propagates an ensemble of neutrinos through given media. Neutrino oscillation calculations relevant to current and next-generation experiments are implemented. This includes coherent and non-coherent neutrino interactions in settings such as the Sun, Earth, or a vacuum. The code is designed to be accurate and flexible, while at the same time maintaining good performance. It has a modular design that allows the user to incorporate new physics in novel scenarios. Program summaryProgram title: Neutrino Simple Quantum Integro-Differential SolverCPC Library link to program files:https://doi.org/10.17632/fb66sr79dz.1Developer's repository link:https://github.com/arguelles/nuSQuIDSLicensing provisions: LGPLProgramming language: C++ with optional Python interfaceNature of problem: The evolution of neutrino fluxes includes both coherent flavor changes (oscillations) and non-coherent scattering interactions with matter. Calculating both types of phenomena is necessary for some studies in neutrino physics, and even in cases where it is not required it is convenient to have a full physics description available in a single package.Solution method: The Simple Quantum Integro-Differential Solver (SQuIDS) [1,2] is used to decompose neutrino fields with SU(N) algebras and solve for their evolution with standard ODE solvers (via the GNU Scientific Library [3]). The evolution of the flavor/mass eigenstate relationships are kept updated in parallel with the ODE solution, as are interaction effects with matter. Users may add new material profiles and physics effects.Additional comments including restrictions and unusual features: Vacuum oscillations are computed analytically, simplifying the ODE problem to be solved. This package supports additions to the neutrino flux over the full course of its evolution, allowing direct treatment of extended sources, and averaging of fast oscillations which cannot be experimentally resolved. The package does not currently implement the complex neutrino interactions relevant at low (O(10 GeV)) neutrino energies.

Neutrino–(anti)neutrino forward scattering potential for massive neutrinos at low energies

In this work, we calculate the expression for the potential due to neutrino–(anti)neutrino forward scattering at low energies [Formula: see text] for ultra-relativistic massive neutrinos [Formula: see text], a representative regime within astrophysical scenarios. There is a broadly used expression for this potential in the literature, which, however, lacks an explicit derivation from basic principles of quantum field theory. Therefore, this paper has an intention to guide the reader through the steps and concepts to derive this potential, trying to be clear and pedagogical. Moreover, we used a rigorous approach concerning the massive nature of the neutrinos, using massive quantized neutrino fields throughout the entire process, while the usual approach is to consider massless neutrino fields at the interaction. In this context, we explicitly show the validity of the massless neutrino fields approximation at the ultra-relativistic regime, as expected. As the last step, we connect the potential expression to the density matrix formalism, which is a usual framework for works considering neutrino–neutrino interactions. We also discuss some theoretical details through the paper such as the normal ordering of quantum operators and the implications of massive fields in the neutrino state at its production.

Dark Range of ω In Brans-Dicke Gravity

The variational field equations of Brans-Dicke scalar-tensor theory of gravitation that is coupled to a mass-varying sterile neutrino field are presented in Riemannian and non-Riemannian setting in the language of exterior differential forms over four-dimensional spacetime. In a gravitational plane wave geometry in Rosen coordinates, with the scalar field set equal to a constant, the field equations admit ghost neutrino solutions. These correspond to Majorana spinor configurations for which the total neutrino stress-energy-momentum tensor vanishes. We show here that in the absence of a sterile neutrino in the gravitational wave geometry, there are scalar field configurations for which the total scalar field stress-energy-momentum tensor vanishes for negative values of the Brans-Dicke parameter —3/2 < ω < 0.