MINOS is a long-baseline neutrino oscillation experiment. It consists of two large steel-scintillator tracking calorimeters. The near detector is situated at Fermilab, close to the production point of the NuMI muon-neutrino beam. The far detector is 735 km away, 716 m underground in the Soudan mine, Northern Minnesota. The primary purpose of the MINOS experiment is to make precise measurements of the "atmospheric" neutrino oscillation parameters (Δm<sup>2</sup><sub>atm</sub> and sin<sup>2</sup>2θ<sub>atm</sub>). The oscillation signal consists of an energy-dependent deficit of v<sub>μ</sub> interactions in the far detector. The near detector is used to characterize the properties of the beam before oscillations develop. The two-detector design allows many potential sources of systematic error in the far detector to be mitigated by the near detector observations. This thesis describes the details of the v<sub>μ</sub>-disappearance analysis, and presents a new technique to estimate the hadronic energy of neutrino interactions. This estimator achieves a significant improvement in the energy resolution of the neutrino spectrum, and in the sensitivity of the neutrino oscillation fit. The systematic uncertainty on the hadronic energy scale was re-evaluated and found to be comparable to that of the energy estimator previously in use. The best-fit oscillation parameters of the v<sub>μ</sub>-disappearance analysis, incorporating this new estimator were: Δm<sup>2</sup> = 2.32<sup>+0.12</sup><sub>-0.08</sub> x 10<sup>-3</sup>eV<sup>2</sup> sin<sup>2</sup>2θ > 0.90 (90% C.L.). A similar analysis, using data from a period of running where the NuMI beam was operated in a configuration producing a predominantly V‾<sub>μ</sub> beam, yielded somewhat different best-fit parameters Δ‾m<sup>2</sup> = (3.36<sup>+0.46</sup><sub>-0.40</sub> (stat.}) ± 0.06(syst.)) x 10<sup>-3</sup>eV<sup>2</sup>, sin<sup>2</sup>2‾θ =0.86<sup>+0.11</sup><sub>-0.12</sub>(stat.) ± 0.01(syst.). The tension between these results is intriguing, and additional antineutrino data is currently being taken in order to further investigate this apparent discrepancy.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:543047 |
| Date | January 2011 |
| Creators | Backhouse, Christopher James |
| Contributors | Barr, Giles |
| Publisher | University of Oxford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://ora.ox.ac.uk/objects/uuid:8d074071-fdf4-4d3e-a503-4d8a17b9e8e3 |
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