Münster 2002 – scientific programme

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HK: Physik der Hadronen und Kerne

HK 5: Electromagnetic and Hadronic Probes I

HK 5.3: Talk

Monday, March 11, 2002, 17:15–17:30, D

LIFETIME OF THE Λ–HYPERON BOUND IN HEAVY HYPERNUCLEI — SUMMARY OF THE COSY–13 RESULTS — •Pawel Kulessa — Institut für Kernphysik, Forschungszentrum Jülich, Germany — H. Niewodniczański Institute of Nuclear Physics, Poland

The nonmesonic decay of Λ–hyperons has been investigated by the observation of delayed fission of heavy hypernuclei produced in proton – Au, Bi and U collisions at COSY-Jülich. The lifetime of heavy hypernuclei obtained by the COSY–13 collaboration τ_Λ= (138 ± 6 (stat.) ± 17 (syst.)) ps for p+U, (161±7(stat.)±14(syst.)) ps for p+Bi and (130±13(stat.)±15(syst.)) ps for p+Au are the most accurate result for proton and antiproton induced collisions on these targets so far. This result together gives an average value for the lifetime of heavy hypernuclei with masses A>180: τ_Λ=(145±11)ps. By comparing the lifetimes of light and heavy hypernuclei we found – on the confidence level of 0.98 – a violation of the phenomenological ΔI=1/2 rule known from the the weak mesonic decays of strange particles.