The first measurements of antineutrino charged-current quasielastic ($ umub$ CCQE, $ umu + N to mup + N$) and neutral-current elastic ($ umub$ NCE, $ umu + N to umu + N$) cross sections with $< E_{bar{ u}} >$ $<$ 1 GeV are presented. To maximize the
precision of these measurements, many data-driven background measurements were executed, including a first demonstration of charge separation using a non-magnetized detector. Apart from extending our knowledge of antineutrino interactions by probing a new energy range, these measurements constrain signal and background processes for current and future neutrino oscillation experiments and also carry implications for intra-nuclear interactions.
The MiniBooNE experiment at Fermilab reports results from an analysis of $bar u_e$ appearance data from $11.27 times 10^{20}$ protons on target in antineutrino mode, an increase of approximately a factor of two over the previously reported results.
An event excess of $78.4 pm 28.5$ events ($2.8 sigma$) is observed in the energy range $200<E_ u^{QE}<1250$ MeV. If interpreted in a two-neutrino oscillation model, $bar{ u}_{mu}rightarrowbar{ u}_e$, the best oscillation fit to the excess has a probability of 66% while the background-only fit has a $chi^2$-probability of 0.5% relative to the best fit. The data are consistent with antineutrino oscillations in the $0.01 < Delta m^2 < 1.0$ eV$^2$ range and have some overlap with the evidence for antineutrino oscillations from the Liquid Scintillator Neutrino Detector (LSND). All of the major backgrounds are constrained by in-situ event measurements so non-oscillation explanations would need to invoke new anomalous background processes. The neutrino mode running also shows an excess at low energy of $162.0 pm 47.8$ events ($3.4 sigma$) but the energy distribution of the excess is marginally compatible with a simple two neutrino oscillation formalism. Expanded models with several sterile neutrinos can reduce the incompatibility by allowing for CP violating effects between neutrino and antineutrino oscillations.
The MiniBooNE and SciBooNE collaborations report the results of a joint search for short baseline disappearance of bar{{ u}_{mu}} at Fermilabs Booster Neutrino Beamline. The MiniBooNE Cherenkov detector and the SciBooNE tracking detector observe anti
neutrinos from the same beam, therefore the combined analysis of their datasets serves to partially constrain some of the flux and cross section uncertainties. Uncertainties in the { u}_{mu} background were constrained by neutrino flux and cross section measurements performed in both detectors. A likelihood ratio method was used to set a 90% confidence level upper limit on bar{{ u}_{mu}} disappearance that dramatically improves upon prior limits in the {Delta}m^2=0.1-100 eV^2 region.
The MiniBooNE experiment at Fermilab reports results from an analysis of the combined $ u_e$ and $bar u_e$ appearance data from $6.46 times 10^{20}$ protons on target in neutrino mode and $11.27 times 10^{20}$ protons on target in antineutrino mode.
A total excess of $240.3 pm 34.5 pm 52.6$ events ($3.8 sigma$) is observed from combining the two data sets in the energy range $200<E_ u^{QE}<1250$ MeV. In a combined fit for CP-conserving $ u_mu rightarrow u_e$ and $bar{ u}_{mu}rightarrowbar{ u}_e$ oscillations via a two-neutrino model, the background-only fit has a $chi^2$-probability of 0.03% relative to the best oscillation fit. The data are consistent with neutrino oscillations in the $0.01 < Delta m^2 < 1.0$ eV$^2$ range and with the evidence for antineutrino oscillations from the Liquid Scintillator Neutrino Detector (LSND).
The MiniBooNE experiment at Fermilab has updated its search for u_mu-bar -> u_e-bar oscillations with data collected through May 2011. This represents a statistics increase of 52% over the result published in 2010. The data favor LSND-like oscillat
ions over a background-only hypothesis at the 91.1% confidence level. While the new result remains equally consistent with LSND, the compatibility with the background-only hypothesis is improved. An excess of 38.6 +- 18.5 u_e-like events below 475 MeV is observed, consistent with the observation of such an excess in neutrino mode.
Neutral Current Elastic (NCE) interactions in MiniBooNE are discussed. In the neutrino mode MiniBooNE reported: the flux averaged NCE differential cross section as a function of four-momentum transferred squared, an axial mass M_{A} measurement, and
a measurement of the strange quark spin content of the nucleon, Delta s. In the antineutrino mode we present the background-subtracted data which is compared with the Monte Carlo predictions.
The MiniBooNE experiment has reported a number of high statistics neutrino and anti-neutrino cross sections-among which are the charged current quasi-elastic (CCQE) and neutral current elastic (NCE) neutrino scattering on mineral oil. Recently a stud
y of the neutrino contamination of the anti-neutrino beam has concluded and the analysis of the anti-neutrino CCQE and NCE scattering is ongoing.
The sidereal time dependence of MiniBooNE electron neutrino and anti-electron neutrino appearance data are analyzed to search for evidence of Lorentz and CPT violation. An unbinned Kolmogorov-Smirnov test shows both the electron neutrino and anti-ele
ctron neutrino appearance data are compatible with the null sidereal variation hypothesis to more than 5%. Using an unbinned likelihood fit with a Lorentz-violating oscillation model derived from the Standard Model Extension (SME) to describe any excess events over background, we find that the electron neutrino appearance data prefer a sidereal time-independent solution, and the anti-electron neutrino appearance data slightly prefer a sidereal time-dependent solution. Limits of order 10E-20 GeV are placed on combinations of SME coefficients. These limits give the best limits on certain SME coefficients for muon neutrino to electron neutrino and anti-muon neutrino to anti-electron neutrino oscillations. The fit values and limits of combinations of SME coefficients are provided.
MiniBooNE anti-neutrino charged-current quasi-elastic (CCQE) data is compared to model predictions. The main background of neutrino-induced events is examined first, where three independent techniques are employed. Results indicate the neutrino flux
is consistent with a uniform reduction of $sim$ 20% relative to the largely uncertain prediction. After background subtraction, the $Q^{2}$ shape of $ umub$ CCQE events is consistent with the model parameter $M_{A}$ = 1.35 GeV determined from MiniBooNE $ umu$ CCQE data, while the normalization is $sim$ 20% high compared to the same prediction.
The MiniBooNE experiment is a $ u_muto u_e$ and $bar u_mutobar u_e$ appearance neutrino oscillation experiment at Fermilab. The neutrino mode oscillation analysis shows an excess of $ u_e$ candidate events in the low-energy region. These events are a
nalyzed under the SME formalism, utilizing the short baseline approximation. The preliminary result shows the time independent solution is favored. The relationship with the SME parameters extracted from the LSND experiment is discussed. The systematic error analysis and antineutrino mode analysis are outlined.
