Lifetime of the Bose Gas with Resonant Interactions

We study the lifetime of a Bose gas at and around unitarity using a Feshbach resonance in lithium 7. At unitarity, we measure the temperature dependence of the three-body decay coefficient L₃. Our data follow a L₃=λ₃/T² law with ${{λ}}₃=2.5(3{)}ₛₜₐₜ(6{)}syst×{}{10}^{{-}20} ({μ}K{)}² {cm}⁶ {s}^{{-}1}$ and are in good agreement with our analytical result based on zero-range theory. Varying the scattering length $a$ at fixed temperature, we investigate the crossover between the finite-temperature unitary region and the previously studied regime where $|a|$ is smaller than the thermal wavelength. We find that ${L}₃$ is continuous across the resonance, and over the whole $a<0$ range our data quantitatively agree with our calculation.