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MINOS Document 3796-v1

Observation of deficit in NuMI neutrino-induced rock and non-fiducial muons in MINOS Far Detector and measurement of neutrino oscillation parameters

Document #:
MINOS-doc-3796-v1
Document type:
Thesis
Submitted by:
Aaron McGowan
Updated by:
Aaron McGowan
Document Created:
01 Nov 2007, 16:08
Contents Revised:
01 Nov 2007, 16:08
Metadata Revised:
16 Jan 2009, 16:42
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Abstract:
The MINOS (Main Injector Neutrino Oscillation Search) experiment has observed\cite{michael2006} muon neutrino disappearance consistent with the oscillation hypothesis tested by Super-Kamiokande\cite{ashie2005}\cite{hosaka2006} and K2K\cite{aliu2005}\cite{ahn2006}. The survival probability for \numu is given approximately by $1 - \sstt\ssdmsqloe$, where \thmutau and \dmsq are the mixing angle and difference in mass squared in eV$^2$/c$^4$ between the mass eigenstates \nuthree and \nutwo, $L$ is the distance traveled in km, and $E$ is the neutrino energy in GeV. In the Near Detector at Fermilab, a measurement of the energy spectrum of the NuMI neutrino beam is made 1 km from the beam target. The neutrinos travel to the Far Detector in the Soudan Underground Laboratory, where another measurement of the energy spectrum is made 735 km from the target. MINOS measures \dmsqabs and \sstt by comparing the ND and FD neutrino energy spectra. In this dissertation, an alternate method is presented that utilizes rock muons, a class of events that occur when a \numu interaction takes place in the rock surrounding the FD. Many muons that result from these interactions penetrate the rock and reach the detector. Muon events from \numu interactions in the non-fiducial volume of the FD are also used in this analysis. The distribution of reconstructed muon momentum and direction relative to the beam is predicted by Monte Carlo simulation, normalized by the measured \numu energy spectrum at the ND. In the first year of NuMI running (an exposure of 1.27\etwenty protons on target) 117 selected events are observed below 3.0 GeV/c, where 150.2$\pm$16.1 events are expected. When a fit is performed to events below 10.0 GeV/c, the null (no disappearance) hypothesis is ruled out at significance level $\alpha=4.2\times10^{-3}$. The data are consistent with the oscillation hypothesis given parameter values
$\dmsqabs = 2.32\pm^{1.06}_{0.75} \times10^{-3}$ eV$^2/c^4$ (stat+sys) and $\sstt > 0.48$ (68\% C.L.)
which is in agreement with the published MINOS result
$\dmsqabs = 2.74\pm^{0.44}_{0.26}\times10^{-3}$ eV$^2/c^4$ (stat+sys) and $\sstt > 0.87$ (68\% C.L.).
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Ph.D. thesis defended by Aaron M. McGowan on 29 August 2007 for graduation from the University of Minnesota.
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