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MINOS Document 7615-v1

Electron Neutrino Appearance in the MINOS Experiment

Document #:
MINOS-doc-7615-v1
Document type:
Thesis
Submitted by:
Anna M Holin
Updated by:
Anna M Holin
Document Created:
29 Sep 2010, 06:12
Contents Revised:
29 Sep 2010, 06:12
Metadata Revised:
21 May 2012, 11:05
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Abstract:
The MINOS experiment is a long-baseline neutrino oscillation experiment which sends a high intensity muon neutrino beam through two functionally identical detectors, a Near detector at the Fermi National Accelerator Laboratory in Illinois, 1km from the beam source, and a Far detector, 734km away, in the Soudan Mine in Minnesota.

MINOS may be able to measure the neutrino mixing angle parameter $sin^{2}2\theta_{13}$ for the first time. Detector granularity, however, makes it very hard to distinguish any $\nu_{e}$ appearance signal events characteristic of a non-zero value of $\theta_{13}$ from background neutral current (NC) and short-track $\nu_{\mu}$ charged current (CC) events. Also, uncertainties in the hadronic shower modeling in the kinematic region characteristic of this analysis are relatively large. A new data-driven background decomposition method designed to address those issues is developed and its results presented. By removing the long muon tracks from $\nu_{\mu}$-CC events, the Muon Removed Charge Current (MRCC) method creates independent pseudo-NC samples that can be used to correct the MINOS Monte Carlo to agree with the high-statistics Near detector data and to decompose the latter into components so as to predict the expected Far detector background. The MRCC method also provides an important cross-check in the Far detector to test the background in the signal selected region.

MINOS finds a 1.0-1.5 $\sigma$ $\nu_{e}$-CC excess above background in the Far detector data, depending on method used, for a total exposure of 3.14×1020 protons-on-target. Interpreting this excess as signal, MINOS can set limits on $sin^{2}2\theta_{13}$. Using the MRCC method, MINOS sets a limit of $sin^{2}2\theta_{13}$ < 0.265 at the 90% confidence limit for a CP-violating phase $\delta$ = 0.

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