Browsing by Subject "Neutrino oscillations"
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Item A search for Large Extra Dimensions with MINOS and MINOS+(2018-06-14) De Rijck, Simon; Lang, Karol, 1955-; Ritchie, Jack; Onyisi, Peter; Andeen, Tim; Gebhardt, KarlThis dissertation presents the search for large extra dimensions using the rich and unique accelerator beam neutrino data collected by the MINOS and MINOS+ experiments from 2005 to 2012 and 2013 to 2016, respectively. Most data from neutrino oscillation experiments are consistent with the standard three-flavor paradigm. With increasing experimental precision, potential effects from physics beyond the Standard Model that could modify neutrino oscillations in subtle ways can be explored. One such scenario involves additional spatial dimensions. Following the Large Extra Dimensions (LED) model, sterile neutrinos arising as Kaluza-Klein states in an extra dimension with size R can mix with the three active neutrinos in 3+1 spacetime, thereby altering the neutrino oscillation probabilities. In addition, this model provides a natural explanation for small Dirac neutrino masses through mass suppression by the volume of the large extra dimensions. In this work, two analysis strategies are employed to search for large extra dimensions: the Far-over-Near analysis and the two-detector analysis. In the former, the ratio of the neutrino energy spectra measured in the MINOS Far and Near Detectors is used to constrain the LED model parameters, while in the latter the measured spectra are used simultaneously. MINOS reported the strongest constraint on R from a neutrino oscillation experiment, constraining R to be smaller than 0.45 µm at 90% C.L. in the limit of a vanishing lightest neutrino mass, using the Far-over-Near approach. Including MINOS+ data, which significantly increases the number of events at higher neutrino energies away from the three-flavor minimum where the model effects are larger, and using the two-detector technique, the size of extra dimensions is further constrained to be smaller than 0.30 µm at 90% C.L. Stronger limits are obtained for non-vanishing lightest neutrino masses.Item Three-flavor neutrino oscillations with MINOS+(2019-08-14) Carroll, Thomas Joseph, III; Lang, Karol, 1955-; Andeen, Timothy; Gebhardt, Karl; Onyisi, Peter; Ritchie, JackThis dissertation presents the analysis of the last two years of data from the MINOS+ long-baseline neutrino oscillation experiment. The analysis explores the data above the first oscillation maximum for neutrinos in the standard three-flavor neutrino oscillation model, adding significantly more neutrino events and constraining the model with increased precision. The analysis of the high-energy region of the MINOS+ data set, where previously there has been limited study, can help constrain alternative models or possibly show evidence of new phenomena. The predecessor to MINOS+, the MINOS experiment, measured [muon neutrino] disappearance and [electron neutrino] appearance using Fermilab's NuMI [muon neutrino] beam from 2005 to 2012. During this period the neutrino beam's energy spectrum was focused to peak near the first oscillation maximum. In addition to measuring accelerator beam neutrinos, the MINOS Far Detector collected a sample of atmospheric neutrinos from 2003 to 2011. With these two samples, MINOS measured the atmospheric mass splitting, Δm²₃₂, at the 5% level and the value of sin²θ₂₃ at the 15% level. The data also constrained the CP violating parameter δ [subscript CP]. The MINOS+ experiment exposed the MINOS detectors to a neutrino beam peaked at energies above the oscillation maximum from 2013 to 2016. With this higher energy neutrino beam, MINOS+ measures the shape of the [muon neutrino] survival probability away from the oscillation maximum with unprecedented precision. Measuring the shape of the oscillation probability as a function of neutrino energy is an essential test of the three-flavor oscillation model. At these higher energies where the standard oscillation probability decreases, the neutrino energy spectrum is sensitive to potential perturbations from mixing with additional sterile neutrinos or non-standard neutrino interactions. This analysis of the complete data set from MINOS+ finds no significant deviations from the three-flavor oscillation probability in the energy region of 4 to 10 GeV covered by the neutrino beam. This provides increased confidence in the three-flavor model in this region and provides new constraints of the atmospheric oscillation parameters, Δm²₃₂ and sin²θ₂₃, by combining the MINOS and MINOS+ data sets. [...] In addition to the analysis and measurement of the atmospheric oscillation parameters using MINOS+, this work updates the constraint on δ [subscript CP] from MINOS and performs an exploratory combination using [muon neutrino] disappearance data from the NOvA experiment. The NOvA experiment uses the NuMI beam in an off-axis strategy that results in a narrow flux of muon neutrinos at the first oscillation maximum and allows precision measurements of the three-flavor parameters. Since NOvA and MINOS+ shared the same neutrino beam, their data can be combined taking advantage of common beam related uncertainties. Combined, the data from the MINOS, MINOS+, and NOvA experiments precisely map [muon neutrino] oscillation probabilities using the same neutrino beam in a way that could not be attempted before.