Title page for ETD etd-03022006-152203


Type of Document Master's Thesis
Author Graham, Nicholas L
Author's Email Address nlgraham@vt.edu
URN etd-03022006-152203
Title Gamma Veto Detectors in the KOPIO Experiment
Degree Master of Science
Department Physics
Advisory Committee
Advisor Name Title
Blecher, Marvin Committee Chair
Pitt, Mark L. Committee Member
Takeuchi, Tatsu Committee Member
Keywords
  • kaon
  • CP violation
  • scintillator
  • fiber optics
Date of Defense 2006-02-05
Availability unrestricted
Abstract
KOPIO is an experiment designed to search for the CP-symmetry-violating

reaction K^0 -> pi^0+nu+nubar. Measurement of the branching ratio of this reaction, depending on

the accuracy of the measurement, could be the most precise measurement of the CP violation

parameters of the Standard Model to date. The K^0 -> pi^0+nu+nubar reaction is

exceedingly rare, with an expected branching ratio of (3 ± 2)⋅10^(−11) . The rareness of this

reaction means two things: 1) that we need prodigious numbers of kaons, and 2) that a

multitude of “improper” decays will have to be screened out by means of a veto detector

system, part of which is being designed here at Virginia Tech.

This detector must be able to detect the passage of daughters of the undesired

decay reactions (charged particles and gammas). It must be operational inside a magnetic

field, and must have signal timing fast enough to accommodate the rate at which these

decays occur. A detector consisting of alternating layers of scintillator and lead, with

wavelength-shifting fibers embedded in the scintillator, provides the characteristics

sought after. This paper presents methodology used in design and construction of this

detector, as well as results of signal property tests, using both cosmic rays and gammas as

event triggers. Also included is a discussion on transporting the detector signal outside of

the magnetic field so it can be read by photomultiplier tubes resting outside of the

sweeping magnet.

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