A supercircle description of universal three-body states in two   dimensions
  We consider bound states of asymmetric three-body systems confined to two dimensions. In the universal regime, two energy ratios and two mass ratios provide complete knowledge of the three-body energy measured in units of one two-body energy. The lowest number of stable bound states is produced when one mass is larger than two similar masses. We focus on selected asymmetric systems of interest in cold atom physics. The scaled three-body energy and the two scaled two-body energies are related through an equation for a supercircle whose radius increases almost linearly with three-body energy. The exponents exhibit an increasing behavior with three-body energy. The mass dependence is highly non-trivial. We give a simple relation that predicts the universal three-body energy. 
F. F. Bellotti and T. Frederico and M. T. Yamashita and D. V. Fedorov   and A. S. Jensen and N. T. Zinner
cond-mat.quant-gas cond-mat.mes-hall nucl-th quant-ph