A Double Magnetic Spectrometer for the Study of Hypernuclei Production by K- in Flight

The experimental set-up used to study the production of hyper-nuclei by the (K−, π−) reaction induced by K− of 390 MeV/c with forward emitted π− is described. The momenta of the incident K− and of the emitted π− were measured by a very compact double magnetic spectrometer, non-focusing, with wide aperture. A single magnet with the target in the middle was used for this purpose. Six pairs of multiwire proportional counters (1700 activated wires) placed in front of, inside and after the magnet were used to measure the trajectories of the particles. Particular care was devoted to the trigger of the experiment and mainly to the separation of K− from π− with thin scintillators and threshold Cherenkov counters. A PDP-11/20 on-line computer controlled the experiment. A total energy resolution of 6 MeV (fwhm) on the excitation spectrum of the hypernucleus was obtained. The solid angle for detection of outgoing particles around 0° was of the order of 8×10−2 sr.