Tests of Universal Three-Body Physics in an Ultracold Bose-Fermi Mixture

Recent measurements of Efimov resonances for a number of ultracold atom species have revealed an unexpected universality, in which three-body scattering properties are determined by the van der Waals length of the two-body interaction potential. To investigate whether this universality extends to hetero-nuclear mixtures, we measure loss rate coefficients in an ultracold trapped gas of K-40 and Rb-87 atoms. We find an Efimov-like resonance in the rate of inelastic collisions between (KRb)-K-40-Rb-87 Feshbach molecules and Rb-87 atoms. However, we do not observe any Efimov-related resonances in the rates of inelastic collisions between three atoms. These observations are compared to previous measurements by the LENS group of Efimov resonances in a K-41 and Rb-87 mixture as well as to recent predictions.