共查询到20条相似文献,搜索用时 31 毫秒
1.
Neutrino oscillation experiments provide the first evidence on non-zero neutrino masses and indicate new physics beyond the standard model. With Majorana neutrinos introduced to acquire tiny neutrino masses, it leads to the existence of more than three neutrino species, implying that the ordinary neutrino mixing matrix is only a part of the whole extended unitary mixing matrix and thus no longer unitary. We give a parameterization for a non-unitary neutrino mixing matrix under seesaw framework and further present a method to test the unitarity of the ordinary neutrino mixing matrix. 相似文献
2.
A status report about experimental searches for neutrino masses is given. Direct mass experiments for the three different neutrino flavours are discussed. Under the assumption of neutrino mixing results of experiments looking for neutrino decay and distortions in spectra of weak decays are reported. 相似文献
3.
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
4.
Yuval Grossman 《Pramana》2004,62(2):269-281
Recent neutrino oscillation data teach us that the neutrinos have masses and that they mix. We discuss two ways that can be
used to probe other non-standard leptonic physics. We show that non-standard neutrino interaction can be probed in neutrino
oscillation experiments and discuss sneutrino-antisneutrino mixing. 相似文献
5.
Srubabati Goswami 《Pramana》2003,60(2):261-278
Neutrino oscillation, in which a given flavor of neutrino transforms into another is a powerful tool for probing small neutrino
masses. The intrinsic neutrino properties involved are neutrino mass squared difference Δm
2 and the mixing angle in vacuum θ. In this paper I will summarize the progress that we have achieved in our search for neutrino
oscillation with special emphasis on the recent results from the Sudbury Neutrino Observatory (SNO) on the measurement of
solar neutrino fluxes. I will outline the current bounds on the neutrino masses and mixing parameters and discuss the major
physics goals of future neutrino experiments in the context of the present picture. 相似文献
6.
Recent neutrino experiments suggest strong evidence of tiny neutrino masses and the lepton-flavor mixing. Neutrino-oscillation
solutions for the atmospheric neutrino anomaly and the solar neutrino deficit can determine the texture of the neutrino mass
matrix according to the neutrino mass hierarchies as Type A: , Type B: , and Type C: , where is the i-th generation neutrino mass. In this paper we study the stability of the lepton-flavor mixing matrix against quantum corrections
for all three types of mass hierarchy in the minimal supersymmetric Standard Model with an effective dimension-five operator
which gives the Majorana masses of neutrinos. The relative sign assignments of neutrino masses in each type play crucial role
for the stability against quantum corrections. We find that the lepton-flavor mixing matrix of Type A is stable against quantum
corrections, and that of Type B with the same (opposite) signs of and are unstable (stable). For Type C, the lepton-flavor-mixing matrix approaches the definite unitary matrix according to the
relative sign assignments of the neutrino mass eigenvalues as the effects of quantum corrections become large enough to neglect
the squared mass differences of neutrinos.
Received: 24 June 1999 / Revised version: 23 December 1999 / Published online: 17 March 2000 相似文献
7.
In this paper, we discuss a possibility of studying properties of dark energy in long baseline neutrino oscillation experiments. We consider two types of models of neutrino dark energy. For one type of models the scalar field is taken to be quintessence-like and for the other phantom-like. In these models the scalar fields couple to the neutrinos to give rise to spatially varying neutrino masses. We will show that the two types of models predict different behaviors of the spatial variation of the neutrino masses inside the Earth and consequently result in different signals in long baseline neutrino oscillation experiments. 相似文献
8.
Sudhir K Vempati 《Pramana》2000,55(1-2):277-282
It has been known for sometime that supersymmetric theories with R-parity violation provide a natural framework where small neutrino masses can be generated. We discuss neutrino masses and
mixing in these theories in the presence of trilinear lepton number violating couplings. It will be shown that simultaneous
solutions to solar and atmospheric neutrino problems can be realized in these models. 相似文献
9.
Abstract In recent years, a nonzero value for the neutrino mixing angle θ13 has been successively measured by the international famous reactor oscillation experiments, which is greater than 5 standard deviations. Our study is in the framework of the MSSM, where baryon and lepton numbers are local gauged symmetries (BLMSSM). This model can generate three tiny neutrino masses at the tree level through TeV scale seesaw mechanism. In our paper, we analyze the neutrino masses and their corresponding mixing angles with a "top-down" method, assuming neutrino mass spectrum with normal ordering (NO) and inverted ordering (IO). 相似文献
10.
《Physics letters. [Part B]》1987,194(4):477-481
Observation of the prompt neutronization burst by Kamiokande II is shown to constrain the mixing parameter sin2ϑ of a 10–100 eV mass range neutrino less than 10−7, implying that the neutrino is unlikely to provide the critical mass of the universe except in a special case of a neutrino decoupled from other lighter neutrinos. Model dependent bounds on neutrino masses are also given for a class of neutrino mixing models. 相似文献
11.
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
12.
We show that, in the framework of three light neutrino species with hierarchical masses and assuming no fine tuning between the entries of the neutrino mass matrix, one can use the solar neutrino data to obtain information on the element U(e3) of the lepton mixing matrix. Conversely, a measurement of U(e3) in atmospheric or long baseline accelerator or reactor neutrino experiments would help discriminate between possible oscillation solutions of the solar neutrino problem. 相似文献
13.
Takaaki Kajita 《Pramana》2006,67(4):639-653
Recent results from solar, reactor, atmospheric and long baseline (K2K) experiments are discussed. With the improved data
statistics and analyses, our knowledge on the neutrino masses and mixing angles are steadily improving. T2K is the next generation
neutrino oscillation experiment between J-PARC in Tokai and Super-Kamiokande. This experiment will start in 2009. This experiment
is expected to improve the current knowledge on the neutrino masses and mixings substantially. 相似文献
14.
M. Lindner 《Nuclear Physics B - Proceedings Supplements》2001,100(1-3)
Neutrino factories allow precise measurements of neutrino masses, leptonic mixing angles, leptonic CP-violation and matter effects. Some aspects of matter effects and their role in the disentanglement of parameters in very long baseline neutrino oscillation experiments are discussed. 相似文献
15.
Y. Liao 《The European Physical Journal C - Particles and Fields》2007,49(3):783-789
We consider the simplest extension of the standard electroweak model by one sterile neutrino that allows for neutrino masses
and mixing. We find that its leptonic sector contains much less free physical parameters than previously realized. In addition
to the two neutrino masses, the lepton mixing matrix in charged current interactions involves (n-1) free physical mixing angles
for n generations. The mixing matrix in neutral current interactions of neutrinos is completely fixed by the two masses. Both
interactions conserve CP. We illustrate the phenomenological implications of the model by vacuum neutrino oscillations, tritium
β decay and neutrinoless double β decay. It turns out that, due to the revealed specific structure in its mixing matrix, the
model with any n generations cannot accommodate simultaneously the data by KamLAND, K2K and CHOOZ.
PACS 14.60.Pq; 14.60.St; 23.40.-s 相似文献
16.
In this paper, we discuss a possibility of studying properties of dark energy in long baseline neutrino oscillation experiments. We consider two types of models of neutrino dark energy. For one type of models the scalar field is taken to be quintessence-like and for the other phantom-like. In these models the scalar fields couple to the neutrinos to give rise to spatially varying neutrino masses. We will show that the two types of models predict different behaviors of the spatial variation of the neutrino masses inside the Earth and consequently result in different signals in long baseline neutrino oscillation experiments. 相似文献
17.
The signals observed at the direct detection experiments DAMA, CoGeNT and CRESST could be explained by light WIMPs with sizeable spin-independent cross sections with nucleons. The capture and subsequent annihilation of such particles in the Sun would induce neutrino signals in the GeV range which may be observed at Super-Kamiokande. We determine the rate of upward stopping muons and fully contained events at Super-Kamiokande for various possible WIMP annihilation channels. This allows us to provide strong constraints on the cross section of WIMPs with nucleons. We find that the DAMA and CoGeNT signals are inconsistent with standard thermal WIMPs annihilating dominantly into neutrino or tau pairs. We also provide limits for spin-dependent WIMP nucleus scattering for masses up to 80 GeV. These exclude the DAMA favored region if WIMPs annihilate even subdominantly into neutrinos, taus, bottoms or charms. 相似文献
18.
The present experimental results on neutrino flavour oscillations provide evidence for non-zero neutrino masses, but give no hint on their absolute mass scale, which is the target of beta decay and neutrinoless double-beta decay experiments. Crucial complementary information on neutrino masses can be obtained from the analysis of data on cosmological observables, such as the anisotropies of the cosmic microwave background or the distribution of large-scale structure. In this review we describe in detail how free-streaming massive neutrinos affect the evolution of cosmological perturbations. We summarize the current bounds on the sum of neutrino masses that can be derived from various combinations of cosmological data, including the most recent analysis by the WMAP team. We also discuss how future cosmological experiments are expected to be sensitive to neutrino masses well into the sub-eV range. 相似文献
19.
We briefly review previous and future reactor experiments aimed at searches for neutrino masses and mixing. We also consider the new idea to seek small mixing-angle oscillations in the atmospheric-neutrinomass-parameter region at Krasnoyarsk. 相似文献
20.
The most recent experimental data on quark and neutrino mixing angles are discussed. It is indicated that the results of the latest kaon-decay experiments are consistent with the unitarity condition for the first row of the Cabibbo-Kobayashi-Maskawa matrix if the currently available world-average value of the neutron lifetime is used to determine the element V ud of this matrix. The quark mixing angles are calculated within the Fritzsch-Scadron-Delbourgo-Rupp phenomenological approach on the basis of values of the masses of light and heavy constituent quarks. The neutrino mixing angles are calculated to a high precision with the aid of the hypothesis that the quark and neutrino mixing angles are complementary. The results are compatible with experimental data. 相似文献