Measurement of the decays psi'. -->. etaJ/psi and psi'. --> pi. /sup 0/J/psi

The Crystal Ball detector at SPEAR has been used to investigate the decays psi'..-->..etaJ/psi and psi'..--> pi../sup 0/J/psi resulting from production of 776 000 psi'. Our measurement for the branching ratio of the eta mode is (2.18 +- 0.14 +- 0.35)%, where the first error results from statistics and acceptance uncertainties, and the second error is systematic; this is almost a factor of 2 smaller than found in early experiments. For the isospin-nonconserving ..pi../sup 0/ mode, a branching ratio (0.09 +- 0.02 +- 0.01)% is obtained.