## Theses and Dissertations

2014

#### Document Type

Open Access Dissertation

#### Department

Physics and Astronomy

Physics

Sanjib R Mishra

#### Abstract

The discovery of neutrino oscillation is a clear evidence of new physics beyond the Standard Model. Measurements of electron neutrino ($\nu_e$) and electron anti-neutrino $\bar{\nu}_{e}$ appearances are the most important channels to complete the neutrino mixing matrix. In a $\nu_{e}$/$\bar{\nu}_{e}$ appearance experiment, a near detector (ND) is used to constrain the neutrino flux and measure the backgrounds to the signal. Backgrounds to the $\nu_{e}$ appearance comes from Neutral Current Muon Neutrino Interactions ($\nu_{\mu}$-NC), Charged Current Muon Neutrino Interactions ($\nu_{\mu}$-CC), beam $\nu_{e}$ events and outside backgrounds. The background components are then extrapolated to the far detector (FD). By looking for excess of signal $\nu_{e}$/$\bar{\nu}_{e}$ -like events in FD, we measure the neutrino mixing angle, neutrino's mass hierarchy and the elusive CP-violation in the lepton sector.

This dissertation focuses on the signals and backgrounds in $\nu_{e}$/$\bar{\nu}_{e}$ appearance measurements. The first part of the dissertation presents an analysis of $\nu_{e}$ appearance in a large Water Cherenkov detector such as the one proposed by the LBNE collaboration. The analysis, including scanning thousands of events, aims to distinguish $\nu_{e}$ signals from the NC backgrounds. The second part of the dissertation presents measurements of Resonance Neutrino Interactions using the NOMAD data. This process plays a critical role in not only neutrino-nuclear cross section but also in the precision analysis of the next generation of neutrino oscillation experiments such as NO$\nu$A and LBNE. The last part of the dissertation discusses the method of using low-$\nu$ fit method to measure relative neutrino flux and constrain beam $\nu_{e}$ background.

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