Searcharxiv⌕ Search

arXiv subjects

W. Grimus

Publications and source records attributed to W. Grimus.

At least 109 records · Page 6Linked to original sources
arXiv1998

Neutrino masses and mixing

We present a short review of the present status of the problem of neutrino masses and mixing. The existing experimental results indicate that there are at least four massive neutrinos. We show that only two schemes with mixing of four neutrinos and mass spectra in which two groups of close masses are separated by the ``LSND gap'' (~ 1 eV) are compatible with the results of all neutrino oscillation experiments. We discuss different consequences of these schemes for future neutrino oscillation experiments.

hep-ph↗
arXiv1998

Four-neutrino mixing and long-baseline neutrino oscillation experiments

We consider the two schemes with four massive neutrinos which are compatible with the results of all neutrino oscillation experiments. We show that in these two schemes the probabilities of nu_e disappearance and nu_mu->nu_e appearance in long-baseline experiments are strongly suppressed.

hep-ph↗
arXiv1998

Neutrino Masses and Mixings in the Light of Experimental Data

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.

hep-ph↗
arXiv1998

Four-Neutrino Mixing and Big-Bang Nucleosynthesis

We investigate the Big-Bang Nucleosynthesis constraints on neutrino mixing in the framework of the two four-neutrino schemes that are favored by the results of neutrino oscillation experiments. We discuss the implications of these constraints for terrestrial short and long-baseline neutrino oscillation experiments and we present some possibilities of testing them in these experiments. In particular, we show that from the Big-Bang Nucleosynthesis constraints it follows that the nu(mu)->nu(tau) transition is severely suppressed in short-baseline experiments, whereas its oscillation amplitude in long-baseline experiments is of order 1. We also propose a new parameterization of the four-neutrino mixing matrix U which is appropriate for the schemes under consideration.

hep-ph↗
arXiv1997

Long-baseline neutrino oscillation experiments and CP violation in the lepton sector

We discuss possibilities to investigate the effects of CP (and T) violation in the lepton sector in neutrino oscillation experiments. We consider the effects of CP violation in the framework of two schemes of mixing of four massive neutrinos that can accommodate the results of all neutrino oscillation experiments. Using the constraints on the mixing parameters that follow from the results of short-baseline neutrino oscillation experiments, we derive rather strong upper bounds on the effects of CP violation in nu_mu<->nu_e transitions in long-baseline neutrino oscillation experiments. We show that the effects of CP violation in nu_mu<->nu_tau transitions in long-baseline oscillation experiments can be as large as is allowed by the unitarity of the mixing matrix. The matter effects, which complicate the problem of searching for CP violation in long-baseline experiments, are discussed in detail. We consider the T-odd asymmetries whose measurement could allow to reveal T and CP violation in the lepton sector independently from matter effects.

hep-ph↗
arXiv1997

Neutrino masses and mixing from neutrino oscillation experiments

We discuss which information on neutrino masses and mixing can be obtained from the results of all neutrino oscillation experiments in the cases of three and four massive neutrinos. We show that in the three-neutrino case the neutrino oscillation data are not compatible with a hierarchy of couplings. In the case of four neutrinos, a hierarchy of masses is disfavored by the data and only two schemes with two pairs of neutrinos with close masses separated by a gap of the order of 1 eV can accommodate the results of all experiments.

hep-ph↗
arXiv1997

Neutrino mixing from neutrino oscillation data

We show that the existing neutrino oscillation data are in favour of the schemes with mixing of four massive neutrinos and that only two of these schemes, with two pairs of neutrinos with close masses separated by a gap of about 1 eV, are compatible with all data. Possible implications of these schemes for future experiments are discussed.

hep-ph↗
arXiv1997

How Devious are Deviations From Quantum Mechanics: The Case of the B^0 \bar B^0 System

Considering semileptonic decays of the entangled B^0 \bar B^0 state which is generated in the decay of Upsilon(4S), we simply multiply the quantum-mechanical interference term by a factor (1-ζ) and use the ``decoherence parameter'' ζas a measure for deviations from quantum mechanics. We investigate several consequences of this modification of semileptonic B^0 \bar B^0 decays. In particular, we show that when confronted with the experimental values of the ratio R=(# like-sign dilepton events)/(# opposite-sign dilepton events) and of the B_H--B_L mass difference, the ensuing one standard deviation range of the decoherence parameter depends strongly on the basis in the B^0--\bar B^0 space used to build the entangled B^0 \bar B^0 state. On the other hand, in quantum mechanics physical quantities are, of course, independent of such arbitrary basis choices.

hep-ph↗
arXiv1997

Effects of neutrino oscillations and neutrino magnetic moments on elastic neutrino-electron scattering

We consider elastic antineutrino-electron scattering taking into account possible effects of neutrino masses and mixing and of neutrino magnetic moments and electric dipole moments. Having in mind antineutrinos produced in a nuclear reactor we compute, in particular, the weak-electromagnetic interference terms which are linear in the magnetic (electric dipole) moments and also in the neutrino masses. We show that these terms are, however, suppressed compared to the pure weak and electromagnetic cross section. We also comment upon the possibility of using the electromagnetic cross section to investigate neutrino oscillations.

hep-ph↗
arXiv1997

Schemes of neutrino mixing from the results of neutrino oscillation experiments

The mixing of three and four massive neutrinos is considered. It is shown that the neutrino oscillation data are not compatible with a hierarchy of couplings in the three-neutrino case. In the case of four neutrinos, a hierarchy of masses is not favored by the data. Only two schemes with two pairs of close masses separated by a gap of the order of 1 eV can accommodate the results of all experiments. If the existing indications in favor of neutrino oscillations will be confirmed, it will mean that the general features of neutrino mixing are quite different from those of quark mixing.

hep-ph↗
arXiv1997

Neutrino masses and mixing from neutrino oscillation data

We discuss what information about the neutrino mass spectrum and the elements of the neutrino mixing matrix can be inferred from the results of neutrino oscillation experiments. The cases of three and four massive neutrinos are considered. It is shown that the general characteristics of the neutrino mixing matrix are quite different from those of the quark mixing matrix.

hep-ph↗
arXiv1997

Constraints on long-baseline neutrino oscillation probabilities and CP asymmetries from neutrino oscillation data

We consider long-baseline neutrino oscillations in the framework of two schemes with mixing of four massive neutrinos which can accommodate all the existing indications in favour of neutrino mixing. Within these schemes, we derive bounds on the oscillation probabilities and the CP-odd neutrino-antineutrino asymmetries in long-baseline experiments. Using the results of short-baseline neutrino oscillation experiments, we obtain rather strong upper bounds on the long-baseline probabilities 1-P(nu_e->nu_e) and P(nu_mu->nu_e). Nevertheless, the projected sensitivities of the MINOS and ICARUS experiments are better than our bounds. We also show that there are no corresponding constraints for nu_mu->nu_mu and nu_mu->nu_tau long-baseline oscillations and that the CP-odd asymmetry in the latter channel can reach the maximal value allowed by the unitarity of the mixing matrix. Some schemes with mixing of three neutrinos are also considered.

hep-ph↗
arXiv1997

Neutrino masses and mixing from neutrino oscillation experiments

What information about the neutrino mass spectrum and mixing matrix can be inferred from the existing neutrino oscillation data? We discuss here the answer to this question in the case of mixing of three and four neutrinos. We present the constraints on the effective Majorana mass that can be obtained from the results of reactor neutrino oscillation experiments and from atmospheric neutrino data. We discuss the bounds on the oscillation probabilities in long-baseline neutrino oscillation experiments that follow from the results of short-baseline experiments. Some remarks on a model-independent approach to the solar neutrino problem are also made.

hep-ph↗
arXiv1996

Quantum-Mechanical Interference over Macroscopic Distances in the B^0 B^0 bar System

We argue that the B^0 B^0 bar state generated in the decay of Upsilon(4S) is well suited for performing tests of Einstein-Podolsky-Rosen correlations, i.e., quantum-mechanical interference effects over macroscopic distances. Using measurements of the ratio R = (#like-sign dilepton events)/(#opposite-sign dilepton events) and of the B_H - B_L mass difference we show that already presently existing data strongly favour the contribution of the interference term to R, as it is required by the rules of quantum mechanics.

hep-ph↗
arXiv1996

Neutrino mass spectrum from the results of neutrino oscillation experiments

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 in Tritium and neutrinoless double-beta decay experiments.

hep-ph↗
arXiv1996

On the Determination of $Δm$ and $ΔΓ$ in Tagged $D^0$--$\bar D^0$ Decays

We consider the time dependence of the decays of tagged $D^0$ and $\bar{D}^0$ into CP-conjugate final states $f$ and $\bar{f}$, or into a CP eigenstate $F$. We expand each decay width as $\exp (- Γt)$ times a series in $Γt$, where $Γ$ is the average decay width of the mass eigenstates $D_H$ and $D_L$, and examine the first three terms of the series. We show that experimental information on the coefficients of these terms allows in principle to compute all the relevant mixing parameters. In particular, depending on CP violation or conservation, we discuss the different possibilities to extract $Δm$ and $ΔΓ$, i.e., the mass and decay-width differences of the mass eigenstates. We also comment on consistency conditions among the coefficients of the various decay-width expansions.

hep-ph↗