Weak decays of 4He-Lambda
Abstract
We measured the lifetime and the mesonic and non-mesonic decay rates of the 4He-Lambda hypernucleus. The hypernuclei were created using a 750 MeV/c momentum K- beam on a liquid 4He target by the reaction 4He(K-,pi-)4He-Lambda. The 4He-Lambda lifetime was directly measured using protons from Lambda p -> n p non-mesonic decay (also referred to as proton-stimulated decay) and was found to have a value of tau = 245 +/- 24 ps. The mesonic decay rates were determined from the observed numbers of pi-'s and pi0's as Gamma_pi-/Gamma_tot = 0.270 +/- 0.024 and Gamma_pi0/Gamma_tot = 0.564 +/- 0.036, respectively, and the values of the proton- and neutron-stimulated decay rates were extracted as Gamma_p/Gamma_tot = 0.169 +/- 0.019 and Gamma_n/Gamma_tot <= 0.032 (95% CL), respectively. The effects of final-state interactions and possible 3-body Lambda N N decay contributions were studied in the context of a simple model of nucleon-stimulated decay. Nucleon-nucleon coincidence events were observed and were used in the determination of the non-mesonic branching fractions. The implications of the results of this analysis were considered for the empirical Delta I = 1/2 rule and the decay rates of the 4H-Lambda hypernucleus.
Cite
@article{arxiv.0705.3311,
title = {Weak decays of 4He-Lambda},
author = {J. D. Parker and M. J. Athanas and P. D. Barnes and S. Bart and B. Bassalleck and R. Chrien and G. Diebold and G. B. Franklin and K. Johnston and P. Pile and B. Quinn and F. Rozon and R. Sawafta and R. A. Schumacher and R. Stearns and I. Sukaton and R. Sutter and J. J. Szymanski and V. J. Zeps},
journal= {arXiv preprint arXiv:0705.3311},
year = {2014}
}