Electron identification in and performance of the ND280 Electromagnetic Calorimeter

Abstract

T2K is an off axis neutrino beam experiment with a baseline of 295 km to the far detector, Super-Kamiokande. The near detector, ND280, measures the flux and energy spectra of electron and muon neutrinos in the direction of Super-Kamiokande. An electromagnetic calorimeter constructed from lead and scintillator surrounds the inner detector. Three time projection chambers and two fine grained scintillator detectors sit inside the calorimeter. This thesis describes the development of a particle identification algorithm for the calorimeter and studies how it can enhance a simple electron neutrino analysis. A particle identification algorithm was written for the electromagnetic calorimeter to separate minimally ionising particles, electromagnetic and hadronic showers. A Monte Carlo study suggested that the algorithm produced an electron sample with a relative muon contamination of 10-2 whilst maintaining an electron efficiency of 80%. Data collected at CERN was then used to make comparisons between the Monte Carlo simulation used to train the particle identification, and experimental data. A reasonable agreement was found between the electron data and the Monte Carlo simulation, given that the available calibration framework was still preliminary. Cosmic data agreed well with simulation. The energy resolution of the DsECal for electromagnetic showers was estimated at 9%/√E. An electron neutrino analysis was developed that could be performed on T2K data from the first day of data taking. This analysis anticipated finding 33 +- 10(sys) +- 6(stat) CCQE electron neutrino events and 92 +- 28(sys) +- 10(stat) CCnQE electron neutrino events in the FGD after 12 months of nominal running