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Register a new userObservation of muon intensity variations by season with the MINOS Near Detector
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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.).
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We have searched for sidereal variations in the rate of antineutrino interactions in the MINOS Near Detector. Using antineutrinos produced by the NuMI beam, we find no statistically significant sidereal modulation in the rate. When this result is placed in the context of the Standard Model Extension theory we are able to place upper limits on the coefficients defining the theory. These limits are used in combination with the results from an earlier analysis of MINOS neutrino data to further constrain the coefficients.
We report the first direct observation of muon antineutrinos in the MINOS Far Detector in the current muon-neutrino dominated beam. The magnetic field of the detector is utilized to separate muon neutrinos and antineutrinos event-by-event by identifying the charge sign of the muon created in charged-current interactions. We present preliminary results on the muon antineutrino oscillation parameters as well as limit on the fraction of neutrinos that disappear and reappear as antineutrinos. We also discuss the prospect of the measurement when the polarity of the magnetic focusing horns will be reversed to create a dedicated muon antineutrino beam.
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.
This letter reports results from the MINOS experiment based on its initial exposure to neutrinos from the Fermilab NuMI beam. The rate and energy spectra of charged current muon neutrino interactions are compared in two detectors located along the beam axis at distances of 1 km and 735 km. With 1.27 x 10^{20} 120 GeV protons incident on the NuMI target, 215 events with energies below 30 GeV are observed at the Far Detector, compared to an expectation of 336 pm 14.4 events. The data are consistent with muon neutrino disappearance via oscillation with |Delta m^2_{23}| = 2.74^{+0.44}_{-0.26} x 10^{-3} eV^2/c^4 and sin^2(2theta_{23}) > 0.87 (at 60% C.L.).
A hydrogen-like atom consisting of a positive muon and an electron is known as muonium. It is a near-ideal two-body system for a precision test of bound-state theory and fundamental symmetries. The MuSEUM collaboration performed a new precision measurement of the muonium ground-state hyperfine structure at J-PARC using a high-intensity pulsed muon beam and a high-rate capable positron counter. The resonance of hyperfine transition was successfully observed at a near-zero magnetic field, and the muonium hyperfine structure interval of ${ u}_{text{HFS}}$ = 4.463302(4) GHz was obtained with a relative precision of 0.9 ppm. The result was consistent with the previous ones obtained at Los Alamos National Laboratory and the current theoretical calculation. We present a demonstration of the microwave spectroscopy of muonium for future experiments to achieve the highest precision.
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