Quantum Diffractive Universality Signatures in Ensemble Heating

In previous work, we have demonstrated that quantum diffractive collisions between a thermal background gas and a cold, trapped sensor gas follow a universal law for certain collision partners. Specifically, we found that the sensor gas loss rate from a trap of depth U follows a universal function P(U/U_d) of the trap depth scaled by a diffractive energy scale U_d. Here we use this law to predict the evolution of the energy distribution of the sensor gas, and we compare this prediction to experimental measurements and numerical simulations for Rb+Ar collisions. We also generalize the evolution equation for any interaction potential energy surface and show how the measured evolution can be used to identify if a collision pair obeys universality or not.