Searches for new physics at MiniBooNE : sterile neutrinos and mixing freedom

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 294-306).The MiniBooNE experiment was designed to perform a search for Vu --> Ve oscillations in a region of A[delta]sin 2 20very different from that allowed by standard, three neutrino oscillations, as determined by solar and atmospheric neutrino experiments. This search was motivated by the LSND experimental observation of an excess of F/e events in a 1,1 beam which was found compatible with two-neutrino oscillations at [delta]m 2 ~ 1 eV2 and sin2 20 Ve oscillations, MiniBooNE has also performed a search for Vu -->Ve oscillations, which provides a test of the LSND two-neutrino oscillation interpretation that is independent of CP or CPT violation assumptions. This dissertation presents the MiniBooNE Vu -->Ve and Vu --> Ve analyses and results, with emphasis on the latter. While the neutrino search excludes the two-neutrino oscillation interpretation of LSND at 98% C.L., the antineutrino search shows an excess of events which is in agreement with the two neutrino Vu -->Ve oscillation interpretation of LSND, and excludes the no oscillations hypothesis at 96% C.L. Even though the neutrino and antineutrino oscillation results from MiniBooNE disagree under the single sterile neutrino oscillation hypothesis, a simple extension to the model to include additional sterile neutrino states and the possibility of CP violation allows for differences between neutrino and antineutrino oscillation signatures. In view of that, the viability of oscillation models with one or two sterile neutrinos is investigated in global fits to MiniBooNE and LSND data, with and without constraints from other oscillation experiments with similar sensitivities to those models. A general search for new physics scenarios which would lead to effective non-unitarity of the standard 3 x 3 neutrino mixing matrix, or mixing freedom, is also performed using neutrino and antineutrino data available from MiniBooNE.by Georgia S. Karagiorgi.Ph.D

Search for Muon Neutrino and Antineutrino Disappearance in MiniBooNE

The MiniBooNE Collaboration reports a search for ν[subscript μ] and ν̅ [subscript μ] disappearance in the Δm[superscript 2] region of 0.5–40   eV[superscript 2]. These measurements are important for constraining models with extra types of neutrinos, extra dimensions, and CPT violation. Fits to the shape of the ν[subscript μ] and ν̅ [subscript μ] energy spectra reveal no evidence for disappearance at the 90% confidence level (C.L.) in either mode. The test of ν̅ [subscript μ] disappearance probes a region below Δm[superscript 2]=40   eV[superscript 2] never explored before.United States Department of EnergyLos Alamos National LaboratoryNational Science FoundationFermi National Accelerator Laborator

First Measurement of the Muon Neutrino Charged Current Quasielastic Double Differential Cross Section

A high-statistics sample of charged-current muon neutrino scattering events collected with the MiniBooNE experiment is analyzed to extract the first measurement of the double differential cross section (d2σ/dTμdcos⁡θμ) for charged-current quasielastic (CCQE) scattering on carbon. This result features minimal model dependence and provides the most complete information on this process to date. With the assumption of CCQE scattering, the absolute cross section as a function of neutrino energy (σ[Eν]) and the single differential cross section (dσ/dQ2) are extracted to facilitate comparison with previous measurements. These quantities may be used to characterize an effective axial-vector form factor of the nucleon and to improve the modeling of low-energy neutrino interactions on nuclear targets. The results are relevant for experiments searching for neutrino oscillations

Improved measurement of neutral current coherent

The SciBooNE Collaboration reports a measurement of neutral current coherent π[superscript 0] production on carbon by a muon neutrino beam with average energy 0.8 GeV. The separation of coherent from inclusive π[superscript 0] production has been improved by detecting recoil protons from resonant π[superscript 0] production. We measure the ratio of the neutral current coherent π0 production to total charged current cross sections to be (1.16 ± 0.24)×10[superscript - 2]. The ratio of charged current coherent π [superscript +] to neutral current coherent π0 production is calculated to be 0.14[subscrit -0.28][superscript +0.30], using our published charged current coherent pion measurement. © 2010 The American Physical Society.United States. Department of EnergyNational Science Foundation (U.S.

Measurement of −inducedcharged−currentneutralpionproductioncrosssectionsonmineraloilat-induced charged-current neutral pion production cross sections on mineral oil at E_nu.5-2.0$ GeV

Using a custom 3-Čerenkov ring fitter, we report cross sections for νμ-induced [nu subscript mu -induced] charged-current single π0 production on mineral oil (CH2) [CH subscript 2] from a sample of 5810 candidate events with 57% signal purity over an energy range of 0.5–2.0 GeV. This includes measurements of the absolute total cross section as a function of neutrino energy, and flux-averaged differential cross sections measured in terms of Q2 Q superscript 2], μ- [mu superscript -] kinematics, and π0 [pi superscript 0] kinematics. The sample yields a flux-averaged total cross section of (9.2±0.3stat±1.5syst)×10-39  [9.2 ± 0.3 subscript stat ± 1.5 subscript syst) times 10 superscript -39] cm2/CH2 [cm superscript 2 / CH supbscript 2] at mean neutrino energy of 0.965 GeV.United States. Dept. of EnergyNational Science Foundation (U.S.)Fermi National Accelerator Laborator