A Hydrogen TPC for the Mucap Experiment - draft June-19-09

The Mucap experiment at the Paul Scherrer Institute is a high-precision measurement of the singlet rate of the basic electroweak process µ - + p → n + νµ (muon capture on the proton). The experimental approach is based on the use of a spec ially developed Time Projection Chamber (TPC) operating with ultra-pure hydrogen gas at 10 bar an d acting as an active muon stop target. Each muon stop in the gas is identified by the TPC and its de cay electron is detected by surrounding wire chambers and a plastic scintillation hodoscope. The TPC allows in connection with the electron detector to measure the μ μ μ μ-p lifetime to highest precision from which the capt ure rate is deduced. The design of the TPC and its experimental performance is described in detail.