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Register a new userMeasurement of a small atmospheric $ u_mu/ u_e$ ratio
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From an exposure of 25.5~kiloton-years of the Super-Kamiokande detector, 900 muon-like and 983 electron-like single-ring atmospheric neutrino interactions were detected with momentum $p_e > 100$ MeV/$c$, $p_mu > 200$ MeV/$c$, and with visible energy less than 1.33 GeV. Using a detailed Monte Carlo simulation, the ratio $(mu/e)_{DATA}/(mu/e)_{MC}$ was measured to be $0.61 pm 0.03(stat.) pm 0.05(sys.)$, consistent with previous results from the Kamiokande, IMB and Soudan-2 experiments, and smaller than expected from theoretical models of atmospheric neutrino production.
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This letter presents a combined measurement of the energy spectra of atmospheric $ u_e$ and $ u_mu$ in the energy range between $sim$100 GeV and $sim$50 TeV with the ANTARES neutrino telescope. The analysis uses 3012 days of detector livetime in the period 2007--2017, and selects 1016 neutrinos interacting in (or close to) the instrumented volume of the detector, yielding shower-like events (mainly from $ u_e+overline u_e$ charged current plus all neutrino neutral current interactions) and starting track events (mainly from $ u_mu + overline u_mu$ charged current interactions). The contamination by atmospheric muons in the final sample is suppressed at the level of a few per mill by different steps in the selection analysis, including a Boosted Decision Tree classifier. The distribution of reconstructed events is unfolded in terms of electron and muon neutrino fluxes. The derived energy spectra are compared with previous measurements that, above 100 GeV, are limited to experiments in polar ice and, for $ u_mu$, to Super-Kamiokande.
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).
We report the first measurement of the atmospheric electron neutrino flux in the energy range between approximately 80 GeV and 6 TeV, using data recorded during the first year of operation of IceCubes DeepCore low energy extension. Techniques to identify neutrinos interacting within the DeepCore volume and veto muons originating outside the detector are demonstrated. A sample of 1029 events is observed in 281 days of data, of which 496 $pm$ 66(stat.) $pm$ 88(syst.) are estimated to be cascade events, including both electron neutrino and neutral current events. The rest of the sample includes residual backgrounds due to atmospheric muons and charged current interactions of atmospheric muon neutrinos. The flux of the atmospheric electron neutrinos is consistent with models of atmospheric neutrinos in this energy range. This constitutes the first observation of electron neutrinos and neutral current interactions in a very large volume neutrino telescope optimized for the TeV energy range.
We report the first observation of off-axis neutrino interactions in the MiniBooNE detector from the NuMI beamline at Fermilab. The MiniBooNE detector is located 745 m from the NuMI production target, at 110 mrad angle ($6.3^{circ}$) with respect to the NuMI beam axis. Samples of charged current quasi-elastic $ u_{mu}$ and $ u_e$ interactions are analyzed and found to be in agreement with expectation. This provides a direct verification of the expected pion and kaon contributions to the neutrino flux and validates the modeling of the NuMI off-axis beam.
MiniBooNE (Mini Booster Neutrino Experiment) searches for the $ u_muto u_e$ oscillations with $Delta m^2 sim 1 eV^2/c^4$ indicated by the LSND experiment. The LSND evidence, when taken with the solar and atmospheric neutrino oscillations, suggests new physics beyond the Standard Model. However, this evidence has not been confirmed by other experiments. MiniBooNE has completed its first $ u_muto u_e$ oscillation search using a sample of $sim 1$ GeV neutrino events obtained with $5.58times 10^{20}$ protons delivered to the Booster Neutrino Beamline. The analysis finds no significant excess of $ u_e$ events in the analysis region of 475-3000 MeV.
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