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The Avalanche Mechanism for Atom Loss near an Atom-Dimer Efimov Resonance

An Efimov trimer near the atom-dimer threshold can increase the atom loss rate in ultracold trapped atoms through the {\it avalanche mechanism} proposed by Zaccanti et al. A 3-body recombination event creates an energetic atom and dimer, whose subsequent elastic collisions produce additional atoms with sufficient energy to escape from the trapping potential. We use Monte Carlo methods to calculate the average number of atoms lost and the average heat generated by recombination events in both a Bose-Einstein condensate and a thermal gas. We take into account the energy-dependence of the cross sections and the spatial structure of the atom cloud. We confirm that the number of atoms lost can be much larger than the naive value 3 if there is an Efimov trimer near the atom-dimer threshold. This does not produce a narrow loss feature, but it can significantly affect the determination of Efimov parameters.