A measurement of the rate of muon capture in an ultra-pure protium gas time projection chamber

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.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2011

Author dc:creator

• Kiburg, Brendan E.

Contributors dc:contributor

• Hertzog, David W.
• Kammel, Peter
• Pitts, Kevin T.
• Eckstein, James N.
• Willenbrock, Scott S.

• muon capture
• weak interaction
• time projection chamber (TPC)
• nuclear physics

Statement dc:rights

• Copyright 2011 Brendan E. Kiburg.

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/26226

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/26226