Bochum 1998 – wissenschaftliches Programm
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HK: Hadronen und Kerne
HK 5: Hadronic Probes I, Protons, Antiprotons, Pions
HK 5.1: Gruppenbericht
Montag, 16. März 1998, 14:00–14:30, C
The lifetime of heavy hypernuclei produced in the 209Bi + p reaction at COSY Jülich — •P. Kulessa1,2, K. Pysz1,2, I. Zychor3, H. Ohm1, Z. Rudy2, B. Kamys2, H.R. Koch1, W. Borgs1, W. Cassing4, L. Jarczyk2, H. Hodde5, R. Maier1, R. Matoba6, D. Prasuhn1, A. Strzalkowski2, and O.W.B. Schult1 — 1Institut für Kernphysik, Forschungszentrum Jülich — 2Institute of Physics, Jagellonian University, Cracow, Poland — 3Soltan Institute for Nuclear Studies, Swierk, Poland — 4Institut für Theoretische Physik, Universität Gießen — 5Institut für Strahlen- und Kernphysik, Universität Bonn — 6Kyushu University, Japan
The lifetime for the nonmesonic decay of heavy hypernuclei has been measured using the internal beam of COSY Jülich with 1.9 GeV protons bombarding a 209Bi target. Identification was done via fragments from Λ-decay induced fission detected with position sensitive MWPCs. Background measurements were performed at 1.0 GeV where the production cross section is negligibly low. The recoil shadow technique was used in order to distinguish between prompt and delayed fission fragments and to deduce the lifetime of the hypernuclei from the position information and the recoil momentum of the hypernuclei. The method is described with emphasis on the effect of the very thin self supporting target on the momentum distribution of the recoiling hypernuclei, on the shape of the position distribution of the shadow events and on the recirculation efficiency of the internal COSY beam. The results are compared with data from 209Bi + e and 209Bi + p reactions and with recent data obtained with 238U targets. Hypernucleus production cross sections will be discussed in the framework of BUU calculations.