  In an Nb film an alternate electrical current is partitioned at a Y-shaped
obstacle into two splitted beams. The intensity-fluctuation correlation of the
two beams (cross-correlation) and the intensity- fluctuation correlation of one
beam (auto-correlation) are measured within a low-frequency bandwidth as a
function of the incident beam intensity, at temperatures T above or below the
temperature Tc of the superconductive transition. The results of these
measurements reveal the statistical nature of the electron gas in the normal
film and in the superconducting film. The conceptual scheme of the present
experiment is a version of the Hanbury Brown and Twiss (HBT) experiment, here
adopted for a gas of particles in a solid.
