Electromagnetic properties of the massive dirac neutrino in an external electromagnetic field

An interpretation of the anomalous magnetic moment of the neutrino is given; we derive an effective Hamiltonian which describes the motion of the neutrino in a weak external magnetic field and calculate the radiation intensity due to the anomalous magnetic moment of the neutrino in a constant magnetic field.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 64–70, March, 1988.     

Limits on the neutrino magnetic moment using 1496 days of Super-Kamiokande-I solar neutrino data

A search for a nonzero neutrino magnetic moment has been conducted using 1496 live days of solar neutrino data from Super-Kamiokande-I. Specifically, we searched for distortions to the energy spectrum of recoil electrons arising from magnetic scattering due to a nonzero neutrino magnetic moment. In the absence of a clear signal, we found micro(nu)相似文献   

Reflection,transmission and spin rotation of dirac neutrinos in magnetic fields

Reflection and transmission coefficients of Dirac neutrinos with a magnetic moment through magnetic fields are calculated. The motion is in three dimensions. We find that one spin component can undergo a total reflection, but the other not, this effect being most pronounced at neutrino energies equal to the magnetic energyμB. We also determine the spin rotation angle (equivalently the helicity rotation angle).     

Neutrino magnetic moment in a magnetized plasma

The magnetized-plasma contribution to the neutrino anomalous magnetic moment is calculated. It is shown that, in a magnetized plasma, only part of the neutrino additional energy associated with the neutrino spin and with the magnetic-field strength contributes to the neutrino magnetic moment. It is found that, in contrast to results presented previously in the literature, the presence of a magnetized plasma does not lead to a substantial enhancement of the neutrino magnetic moment.     

Spin and dispersion of a massive Dirac neutrino in a magnetized plasma

The total energy shift of a polarized massive Dirac neutrino in an electron–positron plasma in a constant magnetic field is investigated. The calculation in the Feynman gauge is performed for the first time by using the Matsubara temperature Green functions. The dependence of the dispersion relation and the anomalous magnetic moment of the neutrino on the magnetic field strength, spin, energy, direction of motion, neutrino mass, and the plasma parameters is analyzed. The results of investigations for the massive neutrino in the limiting case are compared with those obtained earlier by other authors for the massless left neutrino.     

Neutrino mass and magnetic moment in supersymmetry without R-parity in the light of recent data

We consider the generation of neutrino Majorana mass and transition magnetic moment by the lepton-number violating λ and/or λ′ couplings in R-parity-violating supersymmetric models. We update (and improve) the existing upper limits on the relevant couplings using the most recent data on neutrino masses and mixings, indicating also the possible improvement by the GENIUS project. We study the implication of this update on the induced neutrino magnetic moment.     

The electromagnetic mechanism of plasmon decay to a neutrino pair in a strongly magnetized electron gas

An expression for the neutrino luminosity of a degenerate electron gas in a strong magnetic field via plasmon decay to a neutrino pair due to electromagnetic neutrino moments is derived. The neutrino luminosity of the medium in an electromagnetic reaction channel is shown to be comparable with the luminosity in a weak channel. The relative upper bounds for the effective magnetic neutrino moment are obtained.     

Observable seesaw and its collider signatures

We discuss the scenario with TeV-scale right-handed neutrinos, which are accessible at future colliders, while holding down tiny seesaw-induced masses and sizable couplings to the standard-model particles. The signal with tri-lepton final states and large missing transverse energy is appropriate for studying collider signatures of the scenario with extra spatial dimensions. We show that the LHC experiment generally has a potential to discover the signs of extra dimensions and the origin of small neutrino masses.     

Neutrino masses and particle physics beyond the standard model

The evidence for non‐vanishing neutrino masses from solar and atmospheric neutrinos provides the first solid hint towards physics beyond the standard model. A full reconstruction of the neutrino spectrum may well provide a key to the theoretical structures underlying the standard model such as supersymmetry, grand unification or extra space dimensions. In this article we discuss the impact of absolute neutrinos masses on physics beyond the standard model. We review the information obtained from neutrino oscillation data and discuss the prospects of the crucial determination of the absolute neutrino mass scale, as well as the intriguing connection with the Z‐burst model for extreme‐energy cosmic rays.     

Neutrino—nucleon cross-section at ultra-high energies in models with large extra dimensions

We examine whether the models with large extra dimensions can provide an explanation for the GZK violating ultra-high energy cosmic rays (UHECR). In these models the neutrino—nucleon cross-section rises rapidly with energy and hence cosmic rays might be identified with neutrinos. We calculate the neutrino-nucleon cross-section at ultra high energies by assuming that it is dominated by the production ofp-branes. We perform the calculation in a generalized Randall-Sundrum model and Lykken-Randall model and find cross-sections of the order of 100 mb at neutrino energies of 10²⁰ eV, which is required for explaining UHECR events.     

Charge and magnetic moment of the neutrino in the background field method and in the linear R_{\xi}^L gauge

We present a computation of the charge and the magnetic moment of the neutrino in the recently developed electro-weak Background Field Method and in the linear gauge. First, we deduce a formal Ward-Takahashi identity which implies the immediate cancellation of the neutrino electric charge. This Ward-Takahashi identity is as simple as that for QED. The computation of the (proper and improper) one loop vertex diagrams contributing to the neutrino electric charge is also presented in an arbitrary gauge, checking in this way the Ward-Takahashi identity previously obtained. Finally, the calculation of the magnetic moment of the neutrino, in the minimal extension of the Standard Model with massive Dirac neutrinos, is presented, showing its gauge parameter and gauge structure independence explicitly. Received: 6 July 1999 / Revised version: 27 October 1999 / Published online: 27 January 2000     

The search for new physics in nonequilibrium reactor-antineutrino energy spectrum

The calculations of the time-dependent reactor-antineutrino energy spectrum are presented. Some problems associated with sensitive searches for the neutrino magnetic moment and neutrino oscillations in a reactor-antineutrino flux are considered.     

Verifiable model of neutrino masses from large extra dimensions

We propose a new scenario of neutrino masses with a Higgs triplet (xi(++),xi(+),xi(0)) in a theory of large extra dimensions. Lepton number violation in a distant brane acts as the source of a very small trilinear coupling of xi to the standard Higgs doublet in our brane. Small realistic Majorana neutrino masses are naturally obtained with the fundamental scale M(*) approximately O(1) TeV, foretelling the possible discovery of xi (m(xi) less, similarM(*)) at future colliders. Decays of xi(++) into same-sign dileptons are fixed by the neutrino mass matrix. Observation of &mgr;-e conversion in nuclei is predicted.     

Weak and electromagnetic mechanisms of neutrino-pair photoproduction in a strongly magnetized electron gas

Expressions for the power of neutrino radiation from a degenerate electron gas in a strong magnetic field are derived for the case of neutrino-pair photoproduction via the weak and electromagnetic interaction mechanisms (it is assumed that the neutrino possesses electromagnetic form factors). It is shown that the neutrino luminosity of a medium in the electromagnetic reaction channel may exceed substantially the luminosity in the weak channel. Relative upper bounds on the effective neutrino magnetic moment are obtained.     

Dirac-neutrino magnetic moment and the dynamics of a supernova explosion

The double conversion of neutrino chirality ν_L → ν_R → ν_L has been analyzed for supernova conditions, where the first stage is due to the interaction of the neutrino magnetic moment with plasma electrons and protons in the supernova core, and the second stage, due to the resonance spin flip of the neutrino in the magnetic field of the supernova envelope. It is shown that, in the presence of the neutrino magnetic moment in the range 10^?13 μ_B < μ_ν < 10^?12 μ_B and a magnetic field of ～10¹³ G between the neutrinosphere and the shock-stagnation region, an additional energy of about 10⁵¹ erg, which is sufficient for a supernova explosion, can be injected into this region during a typical shock-stagnation time.     

Single and multi-photon events with missing energy in eecollisions at = 189 GeV

Single and multi-photon events with missing energy are analysed using data collected with the L3 detector at LEP at a centre-of-mass energy of 189 GeV, for a total of 176 pb of integrated luminosity. The cross section of the process e⁺e⁻ → γ(γ) is measured and the number of light neutrino flavours is determined to be N_ν=3.011±0.077 including lower energy data. Upper limits on cross sections of supersymmetric processes are set and interpretations in supersymmetric models provide improved limits on the masses of the lightest neutralino and the gravitino. Graviton-photon production in low scale gravity models with extra dimensions is searched for and limits on the energy scale of the model are set exceeding 1 TeV for two extra dimensions.     

Magnetic neutrino scattering on atomic electrons revisited

We reexamine the role of electron binding effects in the inelastic neutrino–atom scattering induced by the neutrino magnetic moment. The differential cross section of the process is presented as a sum of the longitudinal and transverse components, according to whether the force that the neutrino magnetic moment exerts on electrons is parallel or perpendicular to momentum transfer. The atomic electrons are treated nonrelativistically. On this basis, the recent theoretical predictions concerning the magnetic neutrino-impact ionization of atoms are critically discussed. Numerical calculations are performed for ionization of a hydrogenlike Ge⁺³¹ ion by neutrino impact.     

Neutrino scattering on atomic electrons in searches for the neutrino magnetic moment

The scattering of a neutrino on atomic electrons is considered in the situation where the energy transferred to the electrons is comparable to the characteristic atomic energies, as relevant to the current experimental search for the neutrino magnetic moment. The process is induced by the standard electroweak interaction as well as by the possible neutrino magnetic moment. Quantum-mechanical sum rules are derived for the inclusive cross section at a fixed energy deposited in the atomic system, and it is shown that the differential over the energy transfer cross section is given, modulo very small corrections, by the same expression as for free electrons, once all possible final states of the electronic system are taken into account. Thus, the atomic effects effectively cancel in the inclusive process.     

Search for new phenomena using single photon events at LEP1

Data are presented on the reaction e⁺e^? → γ + no other detected particle at centre-of-mass energies of 89.48, 91.26 and 93.08 GeV. The cross-section for this reaction is related directly to the number of light neutrino generations which couple to the Z° boson, and to several other possible phenomena such as the production of excited neutrinos, the production of any invisible ‘X’ particle, and the magnetic moment of the tau neutrino. Based on the observed number of single photon events, the number of light neutrinos that couple to the Z° is measured to be N_v = 2.89 ± 0.38. No evidence is found for anomalous production of energetic single photons, and upper limits at 95% confidence level are determined for excited neutrino production (BR < 4 ? 8 × 10^?6 depending on its mass), production of an invisible ‘X’ particle (σ, < 0.1 pb for masses below 60 GeV), and the magnetic moment of the tau neutrino (< 5.1 × 10^-6 μB).     

Emission and absorption of neutrinos by nonrelativistic neutrons in a magnetic field

The neutrino luminosity of a nonrelativistic nondegenerate neutron gas in a magnetic field owing to the flip of an anomalous magnetic moment, as well as the mean free path of the neutrino due to the absorption in a magnetized neutron gas, has been calculated using the neutron density matrix in the magnetic field obtained in this work. The Fermi energy and partial concentrations of the degenerate neutron gas in the magnetic field have been determined. The astrophysical applications are discussed.