A general formalism is presented for violations of Lorentz and CPT symmetry in the neutrino sector. The effective Hamiltonian for neutrino propagation in the presence of Lorentz and CPT violation is derived, and its properties are studied. Possible definitive signals in existing and future neutrino-oscillation experiments are discussed. Among the predictions are direction-dependent effects, including neutrino-antineutrino mixing, sidereal and annual variations, and compass asymmetries. Other consequences of Lorentz and CPT violation involve unconventional energy dependences in oscillation lengths and mixing angles. A variety of simple models both with and without neutrino masses are developed to illustrate key physical effects. The attainable sensitivities to coefficients for Lorentz violation in the Standard-Model Extension are estimated for various types of experiments. Many experiments have potential sensitivity to Planck-suppressed effects, comparable to the best tests in other sectors. The lack of existing experimental constraints, the wide range of available coefficient space, and the variety of novel effects imply that some or perhaps even all of the existing data on neutrino oscillations might be due to Lorentz and CPT violation.

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Lorentz and CPT violation in neutrinos

Superscaling analyses of few-GeV inclusive electron scattering from nuclei are extended to include not only quasielastic processes, but also the region where $\ensuremath{\Delta}$ excitation dominates. With reasonable assumptions about the basic nuclear scaling function extracted from data and information from other studies of the relative roles played by correlation and meson-exchange-current effects, it is shown that the residual strength in the resonance region can be accounted for through an extended scaling analysis. One observes scaling upon assuming that the elementary cross section by which one divides the residual to obtain a new scaling function is dominated by the $N\ensuremath{\rightarrow}\ensuremath{\Delta}$ transition and employing a new scaling variable suited to the resonance region. This yields a good representation of the electromagnetic response in both the quasielastic and $\ensuremath{\Delta}$ regions. The scaling approach is then inverted and predictions are made for charge-changing neutrino reactions at energies of a few GeV, with focus placed on nuclei that are relevant to neutrino oscillation measurements. For this, a relativistic treatment of the required weak interaction vector and axial-vector currents for both quasielastic and $\ensuremath{\Delta}$-excitation processes is presented.

/pdf/using-electron-scattering-superscaling-to-predict-charge-42pu81lyzx.pdf

Using electron scattering superscaling to predict charge-changing neutrino cross sections in nuclei

We revise the bounds on heavy sterile neutrinos, especially in the case of their mixing with muon neutrinos in the charged current. We summarize the present experimental limits and we reanalyze the existing data from accelerator neutrino experiments and from Super-Kamiokande to set new bounds on a heavy sterile neutrino in the range of masses from 8 MeV to 390 MeV. We also discuss how the future accelerator neutrino experiments can improve the present limits.

http://cds.cern.ch/record/914449/files/jhep112005028.pdf

Bounds on heavy sterile neutrinos revisited

Within the framework of three-flavor neutrino oscillations, we consider the physics potential of {nu}{sub e}{yields}{nu}{sub {mu}} appearance and {nu}{sub {mu}}{yields}{nu}{sub {mu}} survival measurements at a neutrino factory for a leading oscillation scale {delta}m{sup 2}{approx}3.5x10{sup -3} eV{sup 2}. Event rates are evaluated versus baseline and stored muon energy, and optimal values discussed. Over a sizable region of oscillation parameter space, matter effects would enable the sign of {delta}m{sup 2} to be determined from a comparison of {nu}{sub e}{yields}{nu}{sub {mu}} with {nu}(bar sign){sub e}{yields}{nu}(bar sign){sub {mu}} event rates and energy distributions. It is important, therefore, that both positive and negative muons can be stored in the ring. Measurements of the {nu}{sub {mu}}{yields}{nu}{sub {mu}} survival spectrum could determine the magnitude of {delta}m{sup 2} and the leading oscillation amplitude with a precision of O (1%-2%). (c) 2000 The American Physical Society.

Long baseline study of the leading neutrino oscillation at a neutrino factory

The double-differential production cross-section of positive pions, d^2σ^{π+}/d pdΩ, measured in the HARP experiment is presented. The incident particles are 8.9 GeV/c protons directed onto a beryllium target with a thickness of 5% of a nuclear interaction length. The measured cross-section has a direct impact on the prediction of neutrino fluxes for the MiniBooNE and SciBooNE experiments at Fermilab. After cuts, 13 million protons on target produced about 96000 reconstructed secondary tracks which were used in this analysis. Cross-section results are presented in the kinematic range 0.75 GeV/c≤pπ≤ 6.5 GeV/c and 30 mrad≤θπ≤ 210 mrad in the laboratory frame.

/pdf/measurement-of-the-production-cross-section-of-positive-11282tykyg.pdf

Measurement of the production cross-section of positive pions in the collision of 8.9-GeV/c protons on beryllium

A Letter of intent for an experiment to measure muon-neutrino ---> electron-neutrino oscillations and muon-neutrino disappearance at the Fermilab booster (Boone)

This Letter of Intent to the Fermilab Program Advisory Committee describes a search for neutrino oscillations at the Fermilab booster. It is motivated by the LSND observation of nu_mu -> nu_e appearance. The booster neutrino experiment (BooNE) will be capable of observing both nu_mu -> nu_e appearance and nu_mu disappearance. In addition, the experiment will be able to measure Delta m^2 and sin^2(2theta) and search for CP violation in the lepton sector.

T. Ochs

Papers

A Letter of intent for an experiment to measure muon-neutrino ---> electron-neutrino oscillations and muon-neutrino disappearance at the Fermilab booster (Boone)

A letter of intent for an experiment to measure $\nu_\mu$ to $\nu_e$ oscillations and $\nu_\mu$ disappearance at the Fermilab Booster (BooNE)