H. Mes

The spatial resolution of the time projection chamber at triumf

Abstract The spatial resolution of the time projection chamber at TRIUMF has been investigated. The best resolution, σ ⋍ 200 μ m , occurs at the minimum drift length and for an optimum track to anode crossing angle determined by the magnetic field. The resolution worsens for tracks crossing at larger or smaller angles and for longer drift lengths. The observed resolution is quantitatively reproduced by considering the diffusion of the drifting electrons, the track to anode crossing angle, E × B effects near the anode wire and the discrete nature of the ionization process.

Search for muon‐electron and muon‐positron conversion

Limits on the lepton flavor violating reactions ..mu../sup -/+Z..-->..e/sup -/+Z and ..mu../sup -/+Z..-->..e/sup +/+(Z-2), muon-electron and muon-position conversion, have been obtained. Upper limits (90% C.L.) for the branching ratios compared to ordinary muon capture are: R/sub -/(Ti) = GAMMA(..mu../sup -/Ti..-->..e/sup -/Ti)/GAMMA(..mu../sup -/Ti capture) ..d/sup +/Ca*)/GAMMA(..mu../sup -/Ti capture)<1.7 x 10/sup -10/ and R/sub -/(Pb)<4.9 x 10/sup -10/.

The time projection chamber at triumf

The time projection chamber at TRIUMF is being used to search for muon‐electron conversion. The best spatial resolution in the TPC, σ≂200 μm, occurs at the minimum drift length and for an optimum track‐to‐anode crossing angle determined by the magnetic field. The observed resolution is dependent on th diffusion of the drifting electrons, the track‐to‐anode crossing angle, E↘×B↘ effects near the anode wire and the discrete nature of the ionization process. Distortions due to positive ions leaking back into the drift volume from the anode wire region have been nearly eliminated by the use of a pulsed dual grid system.

Search for Muon — to — Electron Conversion in Titanium

The question of muon — to — electron conversion is as old as the muon itself. When it was realised that the muon does not decay into electron and photon the concept of separately conserved muonic and electronic lepton numbers was introduced as an ad hoc hypothesis, without profound justification. But it is only recently that this question has become of great importance, with the advent of the gauge theories of fundamental interactions. The “standard model” based on the electroweak group SU(2) × U(l) with the minimal particle content (no right-handed neutrino, only one Higgs doublet) does not allow any muon number (or any partial lepton number) violation. But the “standard model” is not believed to be the final theory of nature. It has to be modified, generalised, and hopefully embedded in a more complete unification scheme. To do this there are many possibilities which lead to muon number violation in a very natural and inescapable way. Therefore the study of muon number (and other lepton number) violation is one of the most important issues in particle physics. Processes which violate muon number have already been searched for extensively at the meson factories. They have not been observed but very stringent upper limits for their existence have been obtained, which put strong constraints on theoretical models, in particular on mixing parameters and masses of hypothetical particles on the TeV scale. All muon number violating processes are important and must be studied. They will be discussed at length by other speakers at this conference.

Search for muon electron conversion μ−+Ti → e−+Ti

Abstract A progress report on a search for the lepton flavor violating reaction μ − +Ti → e − +Ti is presented. No evidence for this process has yet been found leading to an upper limit −11 (90% confidence level) relative to ordinary muon capture.