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Title:A measurement of the rate of muon capture in an ultra-pure protium gas time projection chamber
Author(s):Kiburg, Brendan E.
Director of Research:Hertzog, David W.; Kammel, Peter
Doctoral Committee Chair(s):Pitts, Kevin T.
Doctoral Committee Member(s):Hertzog, David W.; Kammel, Peter; Eckstein, James N.; Willenbrock, Scott S.
Department / Program:Physics
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):muon capture
weak interaction
time projection chamber (TPC)
nuclear physics
Abstract:The MuCap experiment is designed to measure the disappearance rate of negative muons in an ultra-pure protium gas to a precision of 15 ppm using a time projection chamber (TPC). Combined with precise knowledge of the rate of free muon decay, this determines the capture rate for the mu-p atom in the singlet hyperfine state, L_S, with a precision of 1%. The experimental conditions suppress sensitivity to the poorly known molecular transition rate, l_op, which allows for an unambiguous determination of the proton's pseudoscalar coupling, g_P, with a precision of 6.5%. Chiral perturbation theory makes a precise calculation, g_P = 8.26 +/- 0.23, so a comparison with MuCap's experimental determination of g_P will probe our understanding of low-energy QCD and its underlying symmetries. This dissertation begins with the motivation for the measurement and a summary and brief analysis of previous efforts. The critical role played by the molecular kinetics is described, especially as it is relevant to the design of MuCap and to the analysis of the data. The experimental apparatus and hardware upgrades implemented for the 2007 data collection period are described. The analysis methods are optimized to minimize effects caused by muon physics processes as well as subtle effects caused by interference between muon track and electron signals in the TPC gas. The stability of the disappearance rate with respect to the analysis choices is demonstrated. The remaining systematic studies are summarized, and a relative comparison of L_S between the 2006 and 2007 data sets is reported. The full statistics of 1.5 times 10^10 mu- decays has been collected and analyzed, and a final unblinding of the data will take place in 2011. The final steps to extract g_P with a precision of dg_P = 0.54 from the measured capture rate, L_S, are detailed.
Issue Date:2011-08-25
Rights Information:Copyright 2011 Brendan E. Kiburg.
Date Available in IDEALS:2011-08-25
Date Deposited:2011-08

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