New approach to the observation of the condensate fraction in superfluid helium-4

We present a phenomenological analysis of an experiment to observe the condensate fraction of helium-4 by firing low-energy pulses of helium atoms at suspended droplets of the superfluid and observing the resulting emission of helium atoms from the fluid. Emission occurs through a conventional process in which rotons are produced and propagate to the other side of the droplet, and through a second process depending on the existence of the condensate. If A is the area of the incoming beam, the cross section scales with ${\mathit{A}}^{2}$ (first process) and ${\mathit{A}}^{4}$ (second process), respectively, for small A. Aspects of a fully many body calculation and the performance of such an experiment are briefly discussed.