Hyperdeformed shapes and Jacobi transitions in Ba-126

Systematic searches for exotic shapes, hyperdeformation (HD) and Jacobi transitions, have been made in Hf, Nd, Ba, Xe, Sn and Cd nuclei during the last 4 years, guided by theoretical predictions. The most promising results showing patterns of rotational correlations (e.g. 2. order ridges of multiple rotational bands) are found for Xe-126 and Ba-126 when the very highest multiplicity cascades are selected by various techniques. In particular, the results on Ba-126 obtained in 3 different experiments, using both Gammasphere in Berkeley and Euroball IV in Strasbourg are discussed and compared to theoretical predictions and to simulations by a double-potential statistical model for population and gamma-decay. A very surprising result was obtained in the last experiment at Euroball, in a full month running time, namely that the observed ridge structure depends very sensitively on the bombarding energy, which points to entrance channel effects. The analysis shows that a discrete HD yrast band intensity will be significantly less than 1 part in 10(6) of the strongest bands populated in the reaction.