2019 Impact factor 2.176
Hadrons and Nuclei


Eur. Phys. J. A 11, 1-4 (2001)

Short Note
Nonmesonic decay of the $\Lambda$-hyperon in hypernuclei produced by p + Au collisions

B. Kamys1, P. Kulessa2, H. Ohm2, K. Pysz3, Z. Rudy1, H. Ströher2 and W. Cassing4

1  M. Smoluchowski Institute of Physics, Jagellonian University, PL-30059 Cracow, Poland
2  Institut für Kernphysik, Forschungszentrum Jülich, D-52425 Jülich, Germany
3  H. Niewodniczanski Institute of Nuclear Physics, PL-31342 Cracow, Poland
4  Institut für Theoretische Physik, Justus Liebig Universität Giessen, D-35392 Giessen, Germany

ufrudy@cyf-kr.edu.pl

(Received: 20 November 2000 / Revised version: 12 April 2001 Communicated by Th. Walcher )

Abstract
The lifetime of the $\Lambda$-hyperon for the nonmesonic decay $\Lambda$N $\rightarrow$ NN has been determined by a measurement at COSY Jülich of the delayed fission of heavy hypernuclei produced in proton-Au collisions at $T_{\rm p}=1.9$ GeV. It is found that heavy hypernuclei with mass numbers $A\approx(180\pm5)$ and atomic numbers $Z\approx(74\pm2)$ fission with a lifetime $\tau_{\Lambda}=130 \pm 13$ (stat.) $\pm 15$ (syst.) ps. This value together with the results obtained for other heavy hypernuclei in previous investigations indicates -on the confidence level of 0.9- a violation of the phenomenological $\Delta I=1/2$ rule for the $\Lambda$N $\rightarrow$ NN transitions as known from the weak mesonic decays of kaons and hyperons.

PACS
13.30.-a - Decays of baryons.
13.75.Ev - Hyperon-nucleon interaction.
21.80 - Hypernuclei.
25.80.Pw - Hyperon-induced reactions.

© Società Italiana di Fisica, Springer-Verlag 2001