High Purity Pion Beam at TRIUMF

An extension of the TRIUMF M13 low-energy pion channel designed to suppress positrons based on an energy-loss technique is described. A source of beam channel momentum calibration from the decay pi+ --> e+ nu is also described.Comment: 5 page

Developments in Rare Kaon Decay Physics

We review the current status of the field of rare kaon decays. The study of rare kaon decays has played a key role in the development of the standard model, and the field continues to have significant impact. The two areas of greatest import are the search for physics beyond the standard model and the determination of fundamental standard-model parameters. Due to the exquisite sensitivity of rare kaon decay experiments, searches for new physics can probe very high mass scales. Studies of the k->pnn modes in particular, where the first event has recently been seen, will permit tests of the standard-model picture of quark mixing and CP violation.Comment: One major revision to the text is the branching ratio of KL->ppg, based on a new result from KTeV. Several references were updated, with minor modifications to the text. A total of 48 pages, with 28 figures, in LaTeX; to be published in the Annual Review of Nuclear and Particle Science, Vol. 50, December 200

Precision Measurement of the π+→e+νe Branching Ratio in the PIENU Experiment

The PIENU experiment at TRIUMF aims to measure the branching ratio of the pion decay modes Rπ=[π+→e+νe(γ)]/[π+→μ+νμ(γ)] with precision of <0.1%. Precise measurement of Rπ provides a stringent test of electron-muon universality in weak interactions. The current status of the PIENU experiment and future prospects are presented

A Compact Beam Stop for a Rare Kaon Decay Experiment

We describe the development and testing of a novel beam stop for use in a rare kaon decay experiment at the Brookhaven AGS. The beam stop is located inside a dipole spectrometer magnet in close proximity to straw drift chambers and intercepts a high-intensity neutral hadron beam. The design process, involving both Monte Carlo simulations and beam tests of alternative beam-stop shielding arrangements, had the goal of minimizing the leakage of particles from the beam stop and the resulting hit rates in detectors, while preserving maximum acceptance for events of interest. The beam tests consisted of measurements of rates in drift chambers, scintilation counter hodoscopes, a gas threshold Cherenkov counter, and a lead glass array. Measurements were also made with a set of specialized detectors which were sensitive to low-energy neutrons, photons, and charged particles. Comparisons are made between these measurements and a detailed Monte Carlo simulation.Comment: 39 pages, 14 figures, submitted to Nuclear Instruments and Method

Improved Search for Heavy Neutrinos in the Decay π→eν\pi\rightarrow e\nu

A search for massive neutrinos has been made in the decay $\pi\rightarrow e^+ \nu$. No evidence was found for extra peaks in the positron energy spectrum indicative of pion decays involving massive neutrinos ($\pi\rightarrow e^+ \nu_h$). Upper limits (90 \% C.L.) on the neutrino mixing matrix element $|U_{ei}|^2$ in the neutrino mass region 60--135 MeV/$c^2$ were set, which are %representing an order of magnitude improvement over previous results