Search

Current constraints on neutrino mass and mixing parameters are briefly reviewed, and the prospects for future measurements in long-baseline neutrino experiments are discussed. Parameter degeneracies are a generic problem in the three-neutrino analysis of long-baseline neutrino appearance measurements, and can lead to different inferred values for the neutrino mixing angle θ[sub 13] and often mix CP violating and CP conserving solutions. Possible experimental strategies for reducing or eliminating such degeneracies and/or the CP confusion are discussed. [ABSTRACT FROM AUTHOR]

The ability of neutrino factories and super conventional beams to probe the neutrino mass and mixing parameters is discussed. [Copyright &y& Elsevier]

The physics capabilities of neutrino beams from neutrino factories are briefly presented for both three- and four-neutrino models. [ABSTRACT FROM AUTHOR]

In the context of the Type I seesaw mechanism, we carry out a systematic study of the constraints that result from zeros in both the Dirac and right-handed Majorana neutrino mass matrices. We find that most constraints can be expressed in the standard form with one or two element/cofactor zeros alone, while there are 9 classes of nonstandard constraints. We show that all the constraints are stable under one-loop renormalization group running from the lightest right-handed neutrino mass scale to the electroweak scale. We study the predictions of the nonstandard constraints for the lightest neutrino mass, Dirac CP phase and neutrinoless double beta decay. [ABSTRACT FROM AUTHOR]

We study a model with partial quark-lepton universality that can naturally arise in grand unified theories. We find that constraints on the model can be reduced to a single condition on the Dirac CP phase δ in the neutrino sector. Using our current knowledge of the CKM and PMNS mixing matrices, we predict -32.4°≤δ≤32.0° at 2σ. [ABSTRACT FROM AUTHOR]

Abstract: 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-dependent and direction-independent terms in the effective Hamiltonian is also excluded. [Copyright &y& Elsevier]

Abstract: We perform a comparative study of two methods of determining the survival probabilities of low, intermediate, and high energy solar neutrinos that emphasizes the general agreement between the large mixing angle (LMA) solution and extant solar neutrino data. The first analysis is oscillation parameter-independent and the second analysis involves an approximate calculation of the survival probabilities in the three energy ranges that depends only on oscillation parameters. We show that future experiments like BOREXino, CLEAN, HERON, LENS and MOON, that measure pp and 7Be neutrinos, will facilitate a stringent test of the LMA solution independently of the standard solar model (SSM), without recourse to earth-matter effects. Throughout, we describe the role of SSM assumptions on our results. If the LMA solution passes the test without needing to be modified, it may be possible to establish that is non-zero at more than 2σ assuming the SSM prediction for the pp flux is correct. [Copyright &y& Elsevier]

The LSND signal for ν¯μ→ν¯e oscillations has prompted supposition that there may be a fourth light neutrino or that CPT is violated. Neither explanation provides a good fit to all existing neutrino data. We examine the even more speculative possibility that a four-neutrino model with CPT violation can explain the LSND effect and remain consistent with all other data. We find that models with a 3+1 mass structure in the neutrino sector are viable; a 2+2 structure is permitted only in the antineutrino sector. [Copyright &y& Elsevier]

The current status of the physics of massive neutrinos is reviewed with a forward-looking emphasis. The article begins with the general phenomenology of neutrino oscillations in vacuum and matter and documents the experimental evidence for oscillations of solar, reactor, atmospheric and accelerator neutrinos. Both active and sterile oscillation possibilities are considered. The impact of cosmology (BBN, CMB, leptogenesis) and astrophysics (supernovae, highest energy cosmic rays) on neutrino observables and vice versa, is evaluated. The predictions of grand unified, radiative and other models of neutrino mass are discussed. Ways of determining the unknown parameters of three-neutrino oscillations are assessed, taking into account eight-fold degeneracies in parameters that yield the same oscillation probabilities, as well as ways to determine the absolute neutrino mass scale (from beta-decay, neutrinoless double-beta decay, large scale structure and Z-bursts). Critical unknowns at present are the amplitude of ν[sub μ]→ν[sub e] oscillations and the hierarchy of the neutrino mass spectrum; the detection of CP violation in the neutrino sector depends on these and on an unknown phase. The estimated neutrino parameter sensitivities at future facilities (reactors, superbeams, neutrino factories) are given. The overall agenda of a future neutrino physics program to construct a bottom-up understanding of the lepton sector is presented. [ABSTRACT FROM AUTHOR]

We examine the use of two superbeam neutrino oscillation experiments with baselines ≲1000 km to resolve parameter degeneracies inherent in the three-neutrino analysis of such experiments. We find that with appropriate choices of neutrino energies and baselines two experiments with different baselines can provide a much better determination of the neutrino mass ordering than a single experiment alone. Two baselines are especially beneficial when the mass scale for solar neutrino oscillations δm2sol is ≳5×10-5 eV2. We also examine CP violation sensitivity and the resolution of other parameter degeneracies. We find that the combined data of superbeam experiments with baselines of 295 and 900 km can provide sensitivity to both the neutrino mass ordering and CP violation for sin22θ13 down to 0.03 for &z.sfnc;δm2atm&z.sfnc;=3×10-3 eV2. It would be advantageous to have a 10% determination of &z.sfnc;δm2atm&z.sfnc; before the beam energies and baselines are finalized, although if &z.sfnc;δm2atm&z.sfnc; is not that well known, the neutrino energies and baselines can be chosen to give fairly good sensitivity for a range of &z.sfnc;δm2atm&z.sfnc;. [Copyright &y& Elsevier]

We perform a global analysis in the framework of two active neutrino oscillations of all solar neutrino data, including the recent SNO day and night spectra (comprised of the charged current (CC), elastic scattering (ES) and neutral current (NC) events), the Super-Kamiokande (SK) day and night spectra (from 1496 days) and the updated SAGE results. We find that the Large Mixing Angle (LMA) solution is selected at the 99% C.L.; the best-fit parameters are Δm2=5.6×10−5 eV2 and θ=32°. No solutions with θ⩾π/4 are allowed at the 5σ C.L. Oscillations to a pure sterile state are excluded at 5.3σ, but a sizeable sterile neutrino component could still be present in the solar flux. [Copyright &y& Elsevier]

We examine how constraints can be placed on the neutrino component of dark matter by an accurate measurement of neutrinoless double beta (0νββ) decay and the solar oscillation amplitude. We comment on the alleged evidence for 0νββ decay. [Copyright &y& Elsevier]