Measurement of Single pi0 Production in Neutral Current Neutrino Interactions on Water at the Near Detector of the T2K Experiment

• Main Author: Vallari, Zoya
• Language: EN
• Published: State University of New York at Stony Brook 2019
• Subjects: Physics|High energy physics
• Online Access: http://pqdtopen.proquest.com/#viewpdf?dispub=13423434

<p> T2K is a long baseline neutrino oscillation experiment located in Japan. It was built mainly to detect muon neutrino to electron neutrino oscillation and to measure the mixing angle &thetas;₁₃ of the PMNS matrix, along with the precision measurement of &thetas;₂₃ and mass differences. A &nu;_&mu; beam is produced at the Japan Proton Accelerator Research Complex (J-PARC) in Tokai and travels to the far detector in Kamioka, Japan. There is an ensemble of detectors at 280 m downstream of the target that form the near detector. Super-Kamiokande, a water Cherenkov detector, located 295 km away from the target serves as the far detector. </p><p> The two main backgrounds for electron neutrino appearance at the Super-Kamiokande are the inherent electron neutrino component of the beam and the \pizero{} particle produced via neutral current channel (NC1&pi;⁰) that mimics the electron neutrino interaction signature. To effectively constrain the NC1&pi;⁰ interaction rate on water, the Pi0 Detector (P0D) was built as one of the near detectors. This detector can be filled and drained with water periodically to enable extraction of neutrino interactions on water. </p><p> This analysis measures the NC1&pi;⁰ interaction rate on water in the P0D. It uses neutrino beam data of 3.53 &times; 10²⁰ protons-on-target (POT) for the water-in configuration of the P0D and 6.70 &times; 10²⁰ POT for the water-out configuration. A set of selections are implemented to obtain a sample enriched in signal events. </p><p> The &pi;⁰ invariant mass distribution is compared between data and Monte Carlo. Parameter estimation using Markov Chain Monte Carlo sampling method is performed to measure the signal events in data. </p><p> The data fit results in 130 &plusmn; 20 events on water including both statistical and systematic uncertainties for an expected value of 167 events predicted by the NEUT Monte Carlo. The ratio between nominal Monte Carlo and the best fit value is 0.78 &plusmn; 0.12.</p><p>