LaTeX file, 20 pages, 11 figures. Invited talk at the XXVIII International Symposium on Multiparticle Dynamics, Delphi, Greece, 6-11 September 1998. To be published in the Proceedings, World Scientific, Singapore
Recent results on neutrino oscillations and neutrino masses are presented. The most exciting news are the Super-Kamiokande measurements of atmospheric neutrinos, which show evidence for the neutrinos being massive. Various possible schemes for the neutrino masses are discussed.
Double Chooz experiment will search for a disappearance of the reactor neutrinos from Chooz reactor cores in Ardenne, France, in order to detect the yet unknown neutrino oscillation angle θ13. The far detector was completed in 2010 and data-taking has started in spring 2011. Status of data-taking is presented and some performance plots from physics data are shown in this paper for the first time. Also the prospect of experimental sensitivity is presented, in light of recent indication from T2K for a non-zero θ13 value.
The absolute scale of neutrino masses is very important for understanding the evolution and the structure formation of the universe as well as for nuclear and particle physics beyond the present Standard Model. Complementary to deducing statements on the neutrino mass from cosmological observations two different methods to determine the neutrino mass scale in the laboratory are pursued: the search for neutrinoless double beta decay and the direct neutrino mass search. For both methods currently experiments with a sensitivity of order 100 meV are being set up or commissioned.
CP-symmetry violates in oscillations of neutrinos in vacuum in presence of three generations. In this case there is an inherent complex phase in PMNS-matrix. When any two neutrino masses degenerate the CP-violation vanishes. In the present article different mechanisms of CP-symmetry recovery are demonstrated in case of two degenerate neutrino mass-states.
We show that the combined data from solar, long-baseline and reactor neutrino experiments can exclude the generalized bicycle model of Lorentz noninvariant direction-dependent and/or direction-independent oscillations of massless neutrinos. This model has five parameters, which is more than is needed in standard oscillation phenomenology with neutrino masses. Solar data alone are sufficient to exclude the pure direction-dependent case. The combination of solar and long-baseline data rules out the pure direction-independent case. With the addition of KamLAND data, a mixture of direction-depende…
This essay is intended to provide a brief description of the peculiar properties of neutrinos within and beyond the standard theory of weak interactions. The focus is on the flavor oscillations of massive neutrinos, from which one has achieved some striking knowledge about their mass spectrum and flavor mixing pattern. The experimental prospects towards probing the absolute neutrino mass scale, possible Majorana nature and CP-violating effects will also be addressed.
In this paper, we present the final results of our experiment on photon-axion oscillations in the presence of a magnetic field, which took place at LULI (Laboratoire pour l'Utilisation des Lasers Intenses, Palaiseau, France). Our null measurement allowed us to exclude the existence of axions with inverse coupling constant $M>9.\times 10^5$ GeV for low axion masses and to improve the preceding BFRT limits by a factor 3 or more for axion masses $1.1 {meV} <m_a<2.6 {meV}$. We also show that our experimental results improve the existing limits on the parameters of a low mass hidden-sector boson us…
The recent progress in establishing the existence of finite neutrino masses and mixing between generations of neutrinos has been remarkable, if not astounding. The combined results from studies of atmospheric neutrinos, solar neutrinos, and reactor antineutrinos paint an intriguing picture for theorists and provide clear motivation for future experimental studies. In this review, we summarize the status of experimental and theoretical work in this field and explore the future opportunities that emerge in light of recent discoveries.
Oscillation experiments show that neutrinos have masses. They however only determine the neutrinop mass differences. Information on the absolute masses can be obtained by studying the kinematics in weak decays, or by searching for neutrinoless double beta decay. Recent results are reviewed, as well as future projects.
The question of neutrino mass is one of the major riddles in particle physics. Recently, strong evidence that neutrinos have nonzero masses has been found. While tiny, these masses could be large enough to contribute significantly to the mass density of the universe. The evidence for nonvanishing neutrino masses is based on the apparent observation of neutrino oscillation -- the transformation of a neutrino of one type or "flavor" into one of another. We explain the physics of neutrino oscillation, and review and weigh the evidence that it actually occurs in nature. We also discuss the constra…
We identify a plausible scenario based on quark-lepton symmetry which correlates long baseline oscillations with maximal mixing to sterile neutrinos. The implication for the Sudbury Neutrino Observatory (SNO) is that the neutral current signal will be found to suffer the same suppression from the Standard Solar Model prediction as obtains for the charged current signal. Flavor mixing among active neutrinos is expected to occur on shorter baselines with smaller mixing amplitudes.
The Nobel prize in physics 2015 has been awarded "... for the discovery of neutrino oscillations which show that neutrinos have mass". While SuperKamiokande (SK), indeed, has discovered oscillations, SNO observed effect of the adiabatic (almost non-oscillatory) flavor conversion of neutrinos in the matter of the Sun. Oscillations are irrelevant for solar neutrinos apart from small $ν_e$ regeneration inside the Earth. Both oscillations and adiabatic conversion do not imply masses uniquely and further studies were required to show that non-zero neutrino masses are behind the SNO results. Phenome…
I review explanations for the three neutrino anomalies (solar, atmospheric and LSND) which go beyond the ``conventional'' neutrino oscillations induced by mass-mixing. Several of these require non-zero neutrino masses as well.
Neutrinos exhibit an interesting phenomenon called 'neutrino oscillation', in which a neutrino changes its flavor after traveling some flight length. Many experiments measured the mixing angles and mass differences, but the angle $θ_{13}$ had been unmeasured due to its smallness compared to others. During 2011 and 2012, series of new-generation neutrino experiments reported positive results in $θ_{13}$ search, and its value has been determined to be just below the previous upper limit. The non-zero result of $θ_{13}$ is a very good news for future of neutrino physics, since it opens a possibil…
Within the standard three-neutrino framework, the absolute neutrino masses and their ordering (either normal, NO, or inverted, IO) are currently unknown. However, the combination of current data coming from oscillation experiments, neutrinoless double beta decay searches, and cosmological surveys, can provide interesting constraints for such unknowns in the sub-eV mass range, down to O(0.1) eV in some cases. We discuss current limits on absolute neutrino mass observables by performing a global data analysis, that includes the latest results from oscillation experiments, neutrinoless double bet…
In the present lectures the following topics are considered: general properties of neutrinos, neutrino mass phenomenology (Dirac and Majorana masses), neutrino masses in the simplest extensions of the standard model (including the seesaw mechanism), neutrino oscillations in vacuum, neutrino oscillations in matter (the MSW effect) in 2- and 3-flavour schemes, implications of CP, T and CPT symmetries for neutrino oscillations, double beta decay, solar neutrino oscillations and the solar neutrino problem, and atmospheric neutrinos. We also give a short overview of the results of the accelerator a…
We review the main experimental and theoretical results related to neutrino physics and outline possible lines of developement. The main topics covered are: neutrino masses, oscillations, solar and atmospheric evidences, the LSND/MiniBoone, HM, NuTeV anomalies, future oscillation experiments, beta and 0nu2beta decays, leptogenesis, supernovae, astrophysics, cosmology, flavour models, RGE corrections, violations of lepton flavor in charged leptons, statistics.
By combining experimental constraints from atmospheric and solar neutrino oscillations and the tritium beta decay endpoint, we infer upper limits of 4.4 eV on the $ν_μ$ and $ν_τ$ masses, if the universe consists of three neutrinos. For hierarchical mass spectra $m_3 \gg m_1, m_2$ or $m_3 \simeq m_2 \gg m_1$ we infer that $m_{ν_α} \lsim 0.08$ eV for $α= e, μ, τ$. In a four neutrino universe, and assuming neutrino oscillations also account for the LSND experimental results, $m_{ν_α} \lsim 5.4$ eV. We also obtain lower limits on the masses.
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 (MaVaNs) 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. Both long and short baseline experiments are essential to test for these int…
We present a comprehensive phenomenological analysis of a vast amount of data from neutrino flavor oscillation and non-oscillation searches, performed within the standard scenario with three massive and mixed neutrinos, and with particular attention to subleading effects. The detailed results discussed in this review represent a state-of-the-art, accurate and up-to-date (as of August 2005) estimate of the three-neutrino mass-mixing parameters.