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1.
The vertex function for a virtual massive neutrino is calculated in the limit of soft real photons. A method based on employing the neutrino self-energy operator in a weak external electromagnetic field in the approximation linear in the field is developed in order to render this calculation of the vertex function convenient. It is shown that the electric charge and the electric dipole moment of the real neutrino are zero; only the magnetic moment is nonzero for massive neutrinos. A fourth-generation heavy neutrino of mass not less than half of the Z-boson mass is considered as a massive neutrino. 相似文献
2.
Stanislaw Ciechanowicz Nicolai Popov 《Zeitschrift fur Physik C Particles and Fields》1993,57(4):623-629
Multipole expansion of the partial transition amplitude in the nuclear muon capture with massive lefthanded Dirac neutrino has been derived. The multipole amplitudes for the partial nuclear transitions are given as the explicit functions of the neutrino mass parameter. As an example, the capture rate, the recoil asymmetry and the neutrino polarization are investigated in terms of these multipole amplitudes. The transversal neutrino polarization provides a connection between theT-violation and the neutrino mass: ifT-odd component in the neutrino polarization is observed, then neutrino must be a massive particle. It turns out that in the capture rate and recoil polarization, the effects due to very small neutrino mass can be proportional to the square ratio of the neutrino mass to its momentum, while the neutrino transversal polarization is proportional to this ratio only. Under the recent limits on the muon neutrino mass, the observable effects inthe partial transition may be below the order of ?10?3. 相似文献
3.
C. N. Leung 《Zeitschrift fur Physik C Particles and Fields》1987,35(4):533-536
In a theory of neutrino mixing via a Majorana mass term involving only the left-handed neutrinos there exist selection rules for neutrino oscillations if true Dirac and/or exactly zero mass eigenstates are present. In the case of three neutrino flavours no oscillation is allowed if the mass spectrum contains one Dirac and one nondegenerate Majorana massive neutrino. The origin of these selection rules and their implications are discussed and the number of possible CP-violating phases in the lepton mixing matrix when Dirac and Majorana mass eigenstates coexist is given. 相似文献
4.
By combining data from cosmic microwave background experiments (including the recent WMAP third year results), large scale structure, and Lyman-alpha forest observations, we constrain the hypothesis of a fourth, sterile, massive neutrino. For the 3 massless+1 massive neutrino case, we bound the mass of the sterile neutrino to ms<0.26 eV (0.44 eV) at 95% (99.9%) C.L., which excludes at high significance the sterile neutrino hypothesis as an explanation of the LSND anomaly. We generalize the analysis to account for active neutrino masses and the possibility that the sterile abundance is not thermal. In the latter case, the contraints in the plane are nontrivial. For a mass of >1 or <0.05 eV, the cosmological energy density in sterile neutrinos is always constrained to be omeganu<0.003 at 95% C.L., but for a mass of approximately 0.25 eV, omeganu can be as large as 0.01. 相似文献
5.
Correlation of normal neutrino mass ordering with upper octant of θ_(23) and third quadrant of δ via RGE-induced μ-τ symmetry breaking
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The recent global analysis of three-flavor neutrino oscillation data indicates that the normal neutrino mass ordering is favored over the inverted one at the 3σ level, and the best-fit values of the largest neutrino mixing angle θ_(23) and the Dirac CP-violating phase δ are located in the higher octant and third quadrant, respectively. We show that all these important issues can be naturally explained by the μ-τ reflection symmetry breaking of massive neutrinos from a superhigh energy scale down to the electroweak scale owing to the one-loop renormalization-group equations(RGEs) in the minimal supersymmetric standard model(MSSM). The complete parameter space is explored for the first time in both the Majorana and Dirac cases, by allowing the smallest neutrino mass m1 and the MSSM parameter tanβ to vary within their reasonable regions. 相似文献
6.
Indranath Bhattacharyya 《理论物理通讯》2010,54(2):305-307
Generation of neutrino mass in SO(4) model is proposed here. Thealgebraic structure of SO(4) is same as to that of SU(2)L ×SU(2)R. It is shown that the spontaneous symmetry breaking results three massive as well as three massless gauge bosons. The standard model theory according to which there exist three massive gauge bosons and a massless one is emergedfrom this model. In the framework of SU(2)L × SU(2)R a small Dirac neutrino mass is derived. It is also shown that such mass term may vanish with a special choice. The Majorana mass term is not considered here and thus in this model the neutrino mass does not follow seesaw structure. 相似文献
7.
P. Caban J. Rembieliński K. A. Smoliński Z. Walczak 《Foundations of Physics Letters》2006,19(6):619-623
It is shown that the hypothesis of tachyonic neutrinos leads to the same oscillations effect as if they were usual massive
particles. Therefore, the experimental evidence of neutrino oscillations does not distinguish between massive and tachyonic
neutrinos. Thus, in view of the fact that the results of the direct neutrino mass measurements are not decisive, the question
about the nature of neutrinos remains still open. 相似文献
8.
We consider some cosmological consequences of a relic neutrino asymmetry. A relic neutrino degeneracy enhances the contribution of massive neutrinos to the present energy density of the Universe, and modifies the power spectrum of radiation and matter. We also show that even the smallest neutrino mass consistent with the Super—Kamiokande data is relevant for cosmological models, provided that a relic neutrino asymmetry exists. 相似文献
9.
From the week interaction and the relativistic generalization of the quantum transport equation the volume viscosity of a degenerate massive neutrino gas is derived as a function of the density and the neutrino mass. 相似文献
10.
All the possible schemes of neutrino mixing with four massive neutrinos inspired by the existing experimental indications
in favour of neutrino mixing are considered. It is shown that the scheme with a neutrino mass hierarchy is not compatible
with the experimental results, likewise all other schemes with the masses of three neutrinos close together and the fourth
mass separated by a gap needed to incorporate the LSND neutrino oscillations. Only two schemes with two pairs of neutrinos
with close masses separated by this gap of the order of 1 eV are in agreement with the results of all experiments. We carefully
examine the arguments leading to this conclusion and also discuss experimental consequences of the two favoured neutrino schemes. 相似文献
11.
Summary The problem of the missing matter in the Universe is reviewed and discussed in terms of massive neutrinos. The primordial
abundances of light elements produced during the big bang nucleosynthesis can be used to determine firm bounds on the number
of neutrino flavours and on the ratio of baryon to photon densities in the Universe. These limits imply that nonbaryonic matter
is the dominant constituent of large-scale cosmic structures, being massive neutrinos the best guess for such a matter. In
order that the Universe be closed, a value of the neutrino rest mass is derived, which agrees with the bounds obtained from
the dynamics of galaxies and clusters of galaxies. It is also shown that density perturbations can hardly grow in a nucleon-dominated
Universe, and massive neutrinos may be the seed for nucleon condensations. All these astrophysical and cosmological considerations
suggest a lower and an upper bound of the neutrino rest mass.
Paper presented at the Congress ?Galactic and Extragalactic Dark Matter?, Roma, 28 to 30 June 1983. 相似文献
12.
描述粒子相互作用基本理论是标准模型,按照标准模型,中微子没有静止质量.如果中微子有静止质量,将表现为中微子振荡.戴维斯和小柴昌俊由于确定地发现中微子振荡而获2002年诺贝尔物理奖。 相似文献
13.
We discuss in this paper a stellar model of degenerate massive neutrinos with a core made of heavy matter. Dimension of the core is much smaller than the scale of neutrino star. The Oppenheimer-Volkoff equation is solved for such a system. Our calculation shows that under certain conditions, this neutrino halo will resemble a pure neutrino star. We have further obtained insides the neutrino star (or halo) the rdtation curve and the gravitational red shifts. It is interesting to note that the relative rotation velocity v(r)EV(r)/V(R) (R is the radius of the neutrino star) depends only on the relative coordinate ξ=r/R in the nonrelativistic cases. Therefore, all nonrelativistically degenerate neutrino systems will have a universa1 relative rotation curve(v versus ξ). Within the accuracy of numeri calcalculation, we have also obtained a useful relation connecting the maximum velocity Vm and the corresponding coordinate Rm as VmRm2=0.231. By comparing this relation with the observed rotation data at large distances for some galaxies, we have obtained an upper bound for neutrino mass of about 6-9eV. 相似文献
14.
P. A. Eminov 《Journal of Experimental and Theoretical Physics》2016,122(1):63-77
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. 相似文献
15.
《Physics letters. [Part B]》1988,202(1):47-52
Weakly interacting massive particles (WIMPs) can solve both the solar neutrino and dark matter problems. In this paper we show that a fourth generation Dirac neutrino with mass between 4–10 GeV, in conjunction with the standard, albeit light, Higgs with mass of order 400 MeV, is a candidate WIMP. We describe both the astrophysical and particle physics consequences of this new WIMP. 相似文献
16.
Antonio Díaz Miranda 《International Journal of Theoretical Physics》1996,35(10):2139-2168
A geometrical way is described to associate quantum states in the sense of geometric quantization to wave functions in the
quantum mechanical sense for each relativistic elementary particle. Explicit computations are made in a number of cases: Klein-Gordon
and Dirac equations, neutrino and antineutrino Weyl equations, and very general cases of massive and massless particles of
arbitrary spin. In this later case one is led in a canonical way to Penrose wave equations. 相似文献
17.
S. M. Bilenky C. Giunti W. Grimus 《The European Physical Journal C - Particles and Fields》1998,1(1-2):247-253
All the possible schemes of neutrino mixing with four massive neutrinos inspired by the existing experimental indications in favor of neutrino mixing are considered in a model independent way. Assuming that in short-baseline experiments only one mass-squared difference is relevant, it is shown that the scheme with a neutrino mass hierarchy is not compatible with the experimental results. Only two schemes with two pairs of neutrinos with close masses separated by a mass difference of the order of 1 eV are in agreement with the results of all experiments. One of these schemes leads to possibly observable effects in3H and (β,β)oν experiments. 相似文献
18.
Pablo Alejandro Sánchez 《Physics letters. [Part B]》2011,705(5):535-538
Starting from a Dirac equation for massless neutrino in a 5D Ricci-flat background metric, we obtain the effective 4D equation for massive neutrino in a Schwarzschild-de Sitter (SdS) background metric from an extended SdS 5D Ricci-flat metric. We use the fact that the spin connection is defined to an accuracy of a vector, so that the covariant derivative of the spinor field is strongly dependent of the background geometry. We show that the mass of the neutrino can be induced from the extra space-like dimension. 相似文献
19.
Neutrino mixing is studied in an absolute spacetime conception based on a dispersive aether. The effect of the frequency-dependent permeability of the aether on the interference phase of neutrino mass eigenstates is analyzed. Neutrinos are treated as massless Dirac spinors, and mass eigenstates are due to the neutrino permeability of spacetime. The aether can also generate effective gauge masses, resulting in massive dispersion relations preserving the gauge symmetry. The propagators of gauge and spinor fields are derived, illustrating mass generation by isotropic permeability tensors in the aether frame, the rest frame of the cosmic background radiation. 相似文献
20.
In the supersymmetric left-right model, the light neutrino masses are given by the Type-Ⅱ seesaw mechanism. A duality property of this mechanism indicates that there exist eight possible Higgs triplet Yukawa couplings which result in the same neutrino mass matrix. In this paper, we work out the one-loop renormalization group equations for the effective neutrino mass matrix in the supersymmetric left-right model. The stability of the Type-Ⅱ seesaw scenario is briefly discussed. We also study the lepton-flavor-violating processes (τ→ μγ and τ→eγ) by using the reconstructed Higgs triplet Yukawa couplings. 相似文献