We report a two-detector measurement of the propagation speed of neutrinos over a baseline of 734 km. The measurement was made with the NuMI beam at Fermilab between the near and far MINOS detectors. The fractional difference between the neutrino speed and the speed of light is determined to be $(v/c-1) = (1.0 pm 1.1) times 10^{-6}$, consistent with relativistic neutrinos.
Neutron tagging in Gadolinium-doped water may play a significant role in reducing backgrounds from atmospheric neutrinos in next generation proton-decay searches using megaton-scale Water Cherenkov detectors. Similar techniques might also be useful in the detection of supernova neutrinos. Accurate determination of neutron tagging efficiencies will require a detailed understanding of the number of neutrons produced by neutrino interactions in water as a function of momentum transferred. We propose the Atmospheric Neutrino Neutron Interaction Experiment (ANNIE), designed to measure the neutron yield of atmospheric neutrino interactions in gadolinium-doped water. An innovative aspect of the ANNIE design is the use of precision timing to localize interaction vertices in the small fiducial volume of the detector. We propose to achieve this by using early production of LAPPDs (Large Area Picosecond Photodetectors). This experiment will be a first application of these devices demonstrating their feasibility for Water Cherenkov neutrino detectors.
We report the first observation of seasonal modulations in the rates of cosmic ray multiple-muon events at two underground sites, the MINOS Near Detector with an overburden of 225 mwe, and the MINOS Far Detector site at 2100 mwe. At the deeper site, multiple-muon events with muons separated by more than 8 m exhibit a seasonal rate that peaks during the summer, similar to that of single-muon events. In contrast and unexpectedly, the rate of multiple-muon events with muons separated by less than 5-8 m, and the rate of multiple-muon events in the smaller, shallower Near Detector, exhibit a seasonal rate modulation that peaks in the winter.
Kinematic distributions from an inclusive sample of 1.41 x 10^6 charged-current nu_mu interactions on iron, obtained using the MINOS Near Detector exposed to a wide-band beam with peak flux at 3 GeV, are compared to a conventional treatment of neutrino scattering within a Fermi gas nucleus. Results are used to guide the selection of a subsample enriched in quasielastic nu_mu Fe interactions, containing an estimated 123,000 quasielastic events of incident energies 1 < E_nu < 8 GeV, with <E_nu> = 2.79 GeV. Four additional subsamples representing topological and kinematic sideband regions to quasielastic scattering are also selected for the purpose of evaluating backgrounds. Comparisons using subsample distributions in four-momentum transfer Q^2 show the Monte Carlo model to be inadequate at low Q^2. Its shortcomings are remedied via inclusion of a Q^2-dependent suppression function for baryon resonance production, developed from the data. A chi-square fit of the resulting Monte Carlo simulation to the shape of the Q^2 distribution for the quasielastic-enriched sample is carried out with the axial-vector mass M_A of the dipole axial-vector form factor of the neutron as a free parameter. The effective M_A which best describes the data is 1.23 +0.13/-0.09 (fit) +0.12/-0.15 (syst.) GeV.
A sample of 1.53$times$10$^{9}$ cosmic-ray-induced single muon events has been recorded at 225 meters-water-equivalent using the MINOS Near Detector. The underground muon rate is observed to be highly correlated with the effective atmospheric temperature. The coefficient $alpha_{T}$, relating the change in the muon rate to the change in the vertical effective temperature, is determined to be 0.428$pm$0.003(stat.)$pm$0.059(syst.). An alternative description is provided by the weighted effective temperature, introduced to account for the differences in the temperature profile and muon flux as a function of zenith angle. Using the latter estimation of temperature, the coefficient is determined to be 0.352$pm$0.003(stat.)$pm$0.046(syst.).
We report on a new analysis of neutrino oscillations in MINOS using the complete set of accelerator and atmospheric data. The analysis combines the $ u_{mu}$ disappearance and $ u_{e}$ appearance data using the three-flavor formalism. We measure $|Delta m^{2}_{32}|=[2.28-2.46]times10^{-3}mbox{,eV}^{2}$ (68% C.L.) and $sin^{2}theta_{23}=0.35-0.65$ (90% C.L.) in the normal hierarchy, and $|Delta m^{2}_{32}|=[2.32-2.53]times10^{-3}mbox{,eV}^{2}$ (68% C.L.) and $sin^{2}theta_{23}=0.34-0.67$ (90% C.L.) in the inverted hierarchy. The data also constrain $delta_{CP}$, the $theta_{23}$ octant degeneracy and the mass hierarchy; we disfavor 36% (11%) of this three-parameter space at 68% (90%) C.L.
Neutron tagging in Gadolinium-doped water may play a significant role in reducing backgrounds from atmospheric neutrinos in next generation proton-decay searches using megaton-scale Water Cherenkov detectors. Similar techniques might also be useful in the detection of supernova neutrinos. Accurate determination of neutron tagging efficiencies will require a detailed understanding of the number of neutrons produced by neutrino interactions in water as a function of momentum transferred. We propose the Atmospheric Neutrino Neutron Interaction Experiment (ANNIE), designed to measure the neutron yield of atmospheric neutrino interactions in gadolinium-doped water. An innovative aspect of the ANNIE design is the use of precision timing to localize interaction vertices in the small fiducial volume of the detector. We propose to achieve this by using early production of LAPPDs (Large Area Picosecond Photodetectors). This experiment will be a first application of these devices demonstrating their feasibility for Water Cherenkov neutrino detectors.
We report measurements of oscillation parameters from $ u_{mu}$ and $bar{ u}_{mu}$ disappearance using beam and atmospheric data from MINOS. The data comprise exposures of unit[$10.71 times 10^{20}$]{protons on target (POT)} in the $ u_{mu}$-dominated beam, $unit[3.36times10^{20}]{POT}}$ in the $bar{ u}_{mu}$-enhanced beam, and 37.88 kton-years of atmospheric neutrinos. Assuming identical $ u$ and $bar{ u}$ oscillation parameters, we measure mbox{$|Delta m^2}| = unit[2.41^{+0.09}_{-0.10}) times 10^{-3}]{eV^{2}}$} and $sin^{2}/!/left(2theta right) = 0.950^{+0.035}_{-0.036}$. Allowing independent $ u$ and $bar{ u}$ oscillations, we measure antineutrino parameters of $|Delta bar{m}^2| = unit[(2.50 ^{+0.23}_{-0.25}) times 10^{-3}]{eV^{2}}$ and $sin^{2}/!/left(2bar{theta} right) = 0.97^{+0.03}_{-0.08}$, with minimal change to the neutrino parameters.
We report on $ u_e$ and $bar{ u}_e$ appearance in $ u_mu$ and $bar{ u}_mu$ beams using the full MINOS data sample. The comparison of these $ u_e$ and $bar{ u}_e$ appearance data at a 735 km baseline with $theta_{13}$ measurements by reactor experiments probes $delta$, the $theta_{23}$ octant degeneracy, and the mass hierarchy. This analysis is the first use of this technique and includes the first accelerator long-baseline search for $bar{ u}_murightarrowbar{ u}_e$. Our data disfavor 31% (5%) of the three-parameter space defined by $delta$, the octant of the $theta_{23}$, and the mass hierarchy at the 68% (90%) C.L. We measure a value of 2sin$^2(2theta_{13})$sin$^2(theta_{23})$ that is consistent with reactor experiments.
