Browsing by Author "Buchanan, Norman, committee member"

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Open Access
Independent measurement of the T2K near detector constraint using the off-axis pi-zero detector
(Colorado State University. Libraries, 2019) Hogan, Matthew Gregory, author; Toki, Walter, advisor; Wilson, Robert, committee member; Buchanan, Norman, committee member; Zhou, Wen, committee member
The Tokai to Kamioka (T2K) experiment is a long-baseline neutrino oscillation experiment hosted in Japan searching for electron neutrino appearance in a high purity muon neutrino beam. In order to constrain the systematic uncertainties in the oscillation analysis, a dedicated near detector (ND) complex called ND280 is located 280 meters from the neutrino production source in line of the beam. To date, the Fine Grain Detector (FGD) in ND280 has provided the ND constraint using a binned maximum likelihood estimate fit. This thesis describes the effort to validate the ND constraint using the same framework, but with an independent data set from the ND280 pi-zero detector (PØD). Expanding on previously developed PØD selections, new selections have been developed to select neutrino and antineutrino events in one and multiple track topologies on water and carbon. These selections are shown to have similar sensitivity to the T2K flux and cross section systematic uncertainties. Using the same parameterization as the official ND constraint result, a hypothesis test was conducted between the PØD-only and FGD-only data fit results. A p-value of 0.2865 was obtained indicating the two data sets are likely describing the same population of neutrinos and their interactions in T2K.
Open Access
Measurement of the total flux averaged neutrino induced neutral current elastic scattering cross section with the T2K Pi-Zero detector
(Colorado State University. Libraries, 2014) Ruterbories, Daniel, author; Berger, Bruce E., advisor; Buchanan, Norman, committee member; Lear, Kevin, committee member; Wilson, Robert, committee member
Tokai-to-Kamioka (T2K) is a second generation accelerator neutrino oscillation experiment. T2K uses a high intensity proton beam produced at the Japan Proton Accelerator Research Complex (J-PARC) incident on a carbon target and focused with three magnetic horns to produce a high intensity and nearly pure muon neutrino beam with a peak energy of 600 MeV at a 2.5º axis angle. The muon neutrino beam travels 295 km across Japan to the Super Kamiokande (SK) water Cherenkov detector in the Kamioka mine. The neutrino beam is also sampled by a complex of near detectors 280 m downstream of the carbon target located both on and off the beam axis. These detectors measure the neutrino beam before neutrino oscillations occur to provide input constraints to oscillation searches using SK. The off-axis near detector, ND280, is a composite detector made up of a tracker section and a Pi-Zero detector (PØD), all surrounded by an electromagnetic calorimeter. The entire detector is enclosed in a dipole magnet with a field of 0.2 T. The primary purpose of the tracker section is to measure neutrino induced charged current events characterized by the production of muons. The PØD is primarily designed to detect electromagnetic showers and to measure interactions on water through the use of a removable water target. In addition to these measurements, the ND280 detector is also used to study the cross sections of neutrino interactions on the various materials in the detectors. Limited knowledge of the cross sections in this neutrino energy regime are an important source of systematic error in neutrino oscillation measurements. This thesis presents a measurement of one neutrino interaction channel in the PØD, neutral current elastic scattering (NCE). In this process a neutrino elastically scatters off a proton or neutron in the target nucleus producing a proton or neutron with higher energy. The signature of this process is a single proton track. A particle identification algorithm (PID) was developed to suppress the dominant muon background. Using this algorithm in conjunction with a Michel electron veto the flux averaged absolute cross section is measured to be <σ>flux =2.24×10-39 cm2,nucleon ±0.07(stat.) +0.53,-0.63 (sys.).