Journal article

A TRIGGER FOR THE IDENTIFICATION OF PIONS STOPPED IN AN ACTIVE TARGET

KJ RAYWOOD, AR AMBARDAR, JB LANGE, ME SEVIOR

NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT | ELSEVIER SCIENCE BV | Published : 1995

Abstract

The total cross sections of the π+p → π+π+n and π-p → π+π-n reactions near threshold can be used to obtain scattering lengths which are directly comparable to predictions of chiral perturbation theory. Data for these reactions were taken at TRIUMF using a segmented active scintillator target. The signature of a π+ in an active target segment was a prompt pulse caused by the particle stopping, followed by a second pulse due to the π+ to μ+ decay. TRIUMF 500 Mhz transient digitisers were used to record the scintillator outputs in 2 ns steps so that the double pulses could be identified with high efficiency in off-line data analysis. A second level trigger able to reject events in less than 10 ..

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