共查询到20条相似文献,搜索用时 46 毫秒
1.
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
2.
Superfluid condensation of neutrinos of cosmological origin at a low enough temperature can provide simple and elegant solution to the problems of neutrino oscillations and the accelerated expansion of the universe. It would give rise to a late time cosmological constant of small magnitude and also generate tiny masses for the neutrinos as observed from their flavor oscillations. We show that carefully prepared beta decay experiments in the laboratory would carry signatures of such a condensation, and thus, it would be possible to either establish or rule out neutrino condensation of cosmological scale in laboratory experiments. 相似文献
3.
Daniela P. Kirilova 《Central European Journal of Physics》2004,2(3):467-491
The observational and theoretical status of neutrino oscillations in connection with solar and atmospheric neutrino anomalies
is presented briefly. The effect of neutrino oscillations on the evolution of the early Universe is discussed in detail. A
short review is given of the standard Big Bang Nucleosynthesis (BBN) and the influence of resonant and non-resonant neutrino
oscillations on active neutrinos and on primordial synthesis of He-4. BBN cosmological constraints on neutrino oscillation
parameters are discussed. 相似文献
4.
We present here a scenario, based on a low reheating temperature T(R)<100 MeV at the end of (the last episode of) inflation, in which the coupling of sterile neutrinos to active neutrinos can be as large as experimental bounds permit (thus making this neutrino "visible" in future experiments). In previous models this coupling was forced to be very small to prevent a cosmological overabundance of sterile neutrinos. Here the abundance depends on how low the reheating temperature is. For example, the sterile neutrino required by the Liquid Scintillator Neutrino Detector result may not have any cosmological problem within our scenario. 相似文献
5.
J.W.F. Valle 《Physics letters. [Part B]》1985,159(1):49-56
I show how to accomodate the 17 keV state recently reported by Simpson as one of the neutrinos of the standard model. Experimental constraints can only be satisfied if the μ and τ neutrino combine to a very good approximation to form a Dirac neutrino of 17 keV leaving a light νe. Neutrino oscillations will provide the most stringent test of the model. The cosmological bounds are also satisfied in a natural way in models with Goldstone bosons. Explicit examples are given in the framework of majoron-type models. Constraints on the lepton symmetry breaking scale which follow from astrophysics, cosmology and laboratory experiments are discussed. 相似文献
6.
We consider a class of theories in which neutrino masses depend significantly on environment, as a result of interactions with the dark sector. Such theories of mass varying neutrinos were recently introduced to explain the origin of the cosmological dark energy density and why its magnitude is apparently coincidental with that of neutrino mass splittings. In this Letter we argue that in such theories neutrinos can exhibit different masses in matter and in vacuum, dramatically affecting neutrino oscillations. As an example of modifications to the standard picture, we consider simple models that may simultaneously account for the LSND anomaly, KamLAND, K2K, and studies of solar and atmospheric neutrinos, while providing motivation to continue to search for neutrino oscillations in short baseline experiments such as BooNE. 相似文献
7.
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
8.
We study magnetic dipole moments of right-handed neutrinos in a keV neutrino dark matter model. This model is a simple extension of the standard model with only right-handed neutrinos and a pair of charged particles added. One of the right-handed neutrinos is the candidate of dark matter with a keV mass. Some bounds on the dark matter magnetic dipole moment and model parameters are obtained from cosmological observations. 相似文献
9.
We show how to enlarge the νMSM (the minimal extension of the Standard Model by three right-handed neutrinos) to incorporate inflation and provide a common source for electroweak symmetry breaking and for right-handed neutrino masses. In addition to inflation, the resulting theory can explain simultaneously dark matter and the baryon asymmetry of the Universe; it is consistent with experiments on neutrino oscillations and with all astrophysical and cosmological constraints on sterile neutrino as a dark matter candidate. The mass of inflaton can be much smaller than the electroweak scale. 相似文献
10.
H. V. Klapdor-Kleingrothaus H. Päs U. Sarkar 《The European Physical Journal A - Hadrons and Nuclei》2000,8(4):577-580
We discuss violations of CPT and quantum mechanics due to interactions of neutrinos with space-time quantum foam. Neutrinoless
double beta decay and oscillations of neutrinos from astrophysical sources (supernovae, active galactic nuclei) are analysed.
It is found that the propagation distance is the crucial quantity entering any bounds on EHNS parameters. Thus, while the
bounds from neutrinoless double beta decay are not significant, the data of the supernova 1987a imply a bound being several
orders of magnitude more stringent than the ones known from the literature. Even more stringent limits may be obtained from
the investigation of neutrino oscillations from active galactic nuclei sources, which have an impressive potential for the
search of quantum foam interactions in the neutrino sector.
Received: 5 June 2000 / Accepted: 12 July 2000 相似文献
11.
Christian J 《Physical review letters》2005,95(16):160403
It is pointed out that the Diósi-Penrose ansatz for gravity-induced quantum state reduction can be tested by observing oscillations in the flavor ratios of neutrinos originating at cosmological distances. Since such a test would be almost free of environmental decoherence, testing the ansatz by means of a next generation neutrino detector such as IceCube would be much cleaner than by experiments proposed so far involving superpositions of macroscopic systems. The proposed microscopic test would also examine the universality of the superposition principle at unprecedented cosmological scales. 相似文献
12.
Peter Arnold 《Physics letters. [Part B]》1984,149(6):473-476
We present a symmetry-breaking pattern for SO16 × (U1)PQ which predicts only four super-light neutrinos. Thus, unlike other models of orthogonal family unification, our model satisfies cosmological bounds on neutrino species. 相似文献
13.
A. I. Studenikin 《Physics of Atomic Nuclei》2007,70(7):1275-1287
A brief survey of effects generated by the influence of the environment on neutrinos is presented. The issues considered here include flavor and spin oscillations of neutrinos in matter, in electromagnetic fields of various configurations, and in gravitational fields; the electromagnetic properties of the neutrinos and the environment-induced change in these properties; photoneutrino processes generated by the environment; urca processes in magnetic fields; various mechanisms that may be responsible for the asymmetry of neutrino radiation from neutron stars; quantum states of neutrinos in matter and the spin light of neutrinos in matter and external fields; and astrophysical and cosmological applications of the above processes and phenomena. The method that is employed to describe the effect of the environment on neutrinos (as well as on electrons) and which is based on the application of exact solutions to the corresponding modified Dirac equations for particles in matter is briefly discussed. 相似文献
14.
J G Learned 《Pramana》2000,55(1-2):3-18
With the announcement of new evidence for muon neutrino disappearance observed by the super-Kamiokande experiment, the more
than a decade old atmospheric neutrino anomaly moved from a possible indication for neutrino oscillations to an apparently
inescapable fact. The evidence is reviewed, and new indications are presented that the oscillations are probably between muon
and tau neutrinos. Implications and future directions are discussed. 相似文献
15.
Srubabati Goswami 《Pramana》2000,54(1):173-184
In this article I review the constraints on neutrino mass and mixing coming from type-II supernovae. The bounds obtained on
these parameters from shock reheating, r-process nucleosynthesis and from SN1987A are discussed. Given the current constraints on neutrino mass and mixing the effect
of oscillations of neutrinos from a nearby supernova explosion in future detectors will also be discussed. 相似文献
16.
S. Dutta R. Gandhi B. Mukhopadhyaya 《The European Physical Journal C - Particles and Fields》2000,18(2):405-416
We study the possibilities offered by muon storage rings for appearance experiments in order to determine masses and mixing angles for the and oscillations. The dependence of tau event rates on baseline, forward peaking of decay neutrinos with increasing energies,
and average fluxes intercepted by detectors of various sizes is discussed. It is found that the baseline length does not significantly affect the rates for oscillations of such magnitudes as are suggested by the current atmospheric neutrino data.
Subsequently, the effects of cuts on hadronic and wrong sign leptonic modes are computed and used to plot 90% CL contours
for the parameter regions that can be explored in such experiments. The results show that even for modest muon beam energies,
convincing coverage and verification of the Super Kamiokande parameters is possible. In addition, a very significant enlargement
of present day bounds on the mixing parameters for neutrino oscillations of all types is guaranteed by these types of searches.
Received: 4 April 2000 / Revised version: 22 July 2000 / Published online: 8 December 2000 相似文献
17.
Pontecorvo neutrino oscillations are discussed in the case of Dirac as well as Majorana neutrino mass terms. We prove that none of the possible experiments on neutrino oscillations including those on CP nonconservation, can distinguish between these two possibilities. Oscillations of neutrinos having both Dirac and Majorana mass terms also considered. 相似文献
18.
Anjan S Joshipura 《Pramana》2000,54(1):119-132
The observed deficits in the solar and atmospheric neutrino fluxes along with the accelerator results on neutrino oscillations
significantly constrain possible mass and mixing patterns among neutrinos. We discuss possible patterns emerging from the
experimental results and review theoretical attempts to understand them. 相似文献
19.
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
20.
Steen Hannestad 《Progress in Particle and Nuclear Physics》2010,65(2):185-208
Cosmology provides an excellent laboratory for testing various aspects of neutrino physics. Here, I review the current status of cosmological searches for neutrino mass, as well as other properties of neutrinos. Future cosmological probes of neutrino properties are also discussed in detail. 相似文献