We report the first measurement of monoenergetic muon neutrino charged current interactions. MiniBooNE has isolated 236 MeV muon neutrino events originating from charged kaon decay at rest ...(K^{+}→μ^{+}ν_{μ}) at the NuMI beamline absorber. These signal ν_{μ}-carbon events are distinguished from primarily pion decay in flight ν_{μ} and νover ¯_{μ} backgrounds produced at the target station and decay pipe using their arrival time and reconstructed muon energy. The significance of the signal observation is at the 3.9σ level. The muon kinetic energy, neutrino-nucleus energy transfer (ω=E_{ν}-E_{μ}), and total cross section for these events are extracted. This result is the first known-energy, weak-interaction-only probe of the nucleus to yield a measurement of ω using neutrinos, a quantity thus far only accessible through electron scattering.
The MiniBooNE experiment at Fermilab reports results from an analysis of ν_{e} appearance data from 12.84×10^{20} protons on target in neutrino mode, an increase of approximately a factor of 2 over ...previously reported results. A ν_{e} charged-current quasielastic event excess of 381.2±85.2 events (4.5σ) is observed in the energy range 200<E_{ν}^{QE}<1250 MeV. Combining these data with the νover ¯_{e} appearance data from 11.27×10^{20} protons on target in antineutrino mode, a total ν_{e} plus νover ¯_{e} charged-current quasielastic event excess of 460.5±99.0 events (4.7σ) is observed. If interpreted in a two-neutrino oscillation model, ν_{μ}→ν_{e}, the best oscillation fit to the excess has a probability of 21.1%, while the background-only fit has a χ^{2} probability of 6×10^{-7} relative to the best fit. The MiniBooNE data are consistent in energy and magnitude with the excess of events reported by the Liquid Scintillator Neutrino Detector (LSND), and the significance of the combined LSND and MiniBooNE excesses is 6.0σ. A two-neutrino oscillation interpretation of the data would require at least four neutrino types and indicate physics beyond the three neutrino paradigm. Although the data are fit with a two-neutrino oscillation model, other models may provide better fits to the data.
The MiniBooNE experiment at Fermilab reports results from an analysis of ν¯e appearance data from 11.27×10²⁰ protons on target in the antineutrino mode, an increase of approximately a factor of 2 ...over the previously reported results. An event excess of 78.4±28.5 events (2.8σ) is observed in the energy range 200<EQEν<1250 MeV. If interpreted in a two-neutrino oscillation model, ν¯μ→ν¯e, the best oscillation fit to the excess has a probability of 66% while the background-only fit has a χ² probability of 0.5% relative to the best fit. The data are consistent with antineutrino oscillations in the 0.01<Δm²<1.0 eV² range and have some overlap with the evidence for antineutrino oscillations from the Liquid Scintillator Neutrino Detector. All of the major backgrounds are constrained by in situ event measurements so nonoscillation explanations would need to invoke new anomalous background processes. The neutrino mode running also shows an excess at low energy of 162.0±47.8 events (3.4σ) 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.
We report a study of ν(μ) charged-current quasielastic events in the segmented scintillator inner tracker of the MINERvA experiment running in the NuMI neutrino beam at Fermilab. The events were ...selected by requiring a μ- and low calorimetric recoil energy separated from the interaction vertex. We measure the flux-averaged differential cross section, dσ/dQ², and study the low energy particle content of the final state. Deviations are found between the measured dσ/dQ² and the expectations of a model of independent nucleons in a relativistic Fermi gas. We also observe an excess of energy near the vertex consistent with multiple protons in the final state.
The largest sample ever recorded of charged-current quasielastic (CCQE, nu sub( mu ) + p arrow right mu super(+) + n) candidate events is used to produce the minimally model-dependent, ...flux-integrated double-differential cross section d2sigma/dT sub( mu )dcosstraighttheta sub( mu ) for nu sub( mu ) CCQE for a mineral oil target. This measurement exploits the large statistics of the MiniBooNE antineutrino mode sample and provides the most complete information of this process to date. In order to facilitate historical comparisons, the flux-unfolded total cross section sigma(E sub(nu)) and single-differential cross section dsigma/dQ super(2) on both mineral oil and on carbon are also reported. The observed cross section is somewhat higher than the predicted cross section from a model assuming independently acting nucleons in carbon with canonical form factor values. The shape of the data are also discrepant with this model. These results have implications for intranuclear processes and can help constrain signal and background processes for future neutrino oscillation measurements.
We have isolated ν(μ) charged-current quasielastic (QE) interactions occurring in the segmented scintillator tracking region of the MINERvA detector running in the NuMI neutrino beam at Fermilab. We ...measure the flux-averaged differential cross section, dσ/dQ², and compare to several theoretical models of QE scattering. Good agreement is obtained with a model where the nucleon axial mass, M(A), is set to 0.99 GeV/c² but the nucleon vector form factors are modified to account for the observed enhancement, relative to the free nucleon case, of the cross section for the exchange of transversely polarized photons in electron-nucleus scattering. Our data at higher Q² favor this interpretation over an alternative in which the axial mass is increased.
The surrogate reaction method is a powerful tool to infer neutron-induced data of short-lived nuclei. After a short overview of the experimental techniques employed in the present surrogate ...experiments, we will concentrate on a recent measurement to determine neutron-induced fission cross sections for the actinides 242,243Cm and 241Am. The latest direct neutron-induced measurement for the 243Cm fission cross section is questioned by our results, since there are differences of more than 60% in the 0.7 to 7 MeV neutron energy range. Our experimental set-up has also enabled us to measure for the first time the fission fragment 'pseudo-mass' distributions of 243,244,245Cm and 242Am compound nuclei in the excitation energy range from a few MeV to about 25 MeV.
The
γ-ray emission probability distribution of
234Pa
∗ has been measured between 5.2 and 6.2 MeV excitation energy using the transfer reaction
232Th(
3He, p)
234Pa
∗ at an incident
3He energy of 24 ...MeV. The experimental set-up is made of four liquid scintillator C
6D
6 detectors and four Si telescopes arranged to detect
γ rays and charged particles in coincidence. In order to determine the total number of
γ-ray cascades in a given nucleus, the raw experimental detected gamma-ray events have to be corrected by the weighting function technique. This weighting requires complete knowledge of the efficiency and response functions for the C
6D
6 detector set-up and surroundings. These have been determined experimentally using gamma-ray sources, inelastic scattering reactions and transfer reactions on light nuclei. Simulations which reproduce successfully the detector response and efficiency are presented.
From these measurements, the (n,
γ) capture cross section of
233Pa, in the neutron energy range 0 to 1 MeV, has been deduced via the product of the measured
γ emission probability of
234Pa
∗ with the calculated compound nucleus formation cross section of the reaction
233Pa
+
n. A comparison between existing data bases or recent predictions and the present results is also made.
PDF
