  Soliton gases represent large random soliton ensembles in physical systems
that display integrable dynamics at the leading order. We report hydrodynamic
experiments in which we investigate the interaction between two "beams" or
"jets" of soliton gases having nearly identical amplitudes but opposite
velocities of the same magnitude. The space-time evolution of the two
interacting soliton gas jets is recorded in a 140-m long water tank where the
dynamics is described at leading order by the focusing one-dimensional
nonlinear Schrodinger equation. Varying the relative initial velocity of the
two species of soliton gas, we change their interaction strength and we measure
the macroscopic soliton gas density and velocity changes due to the
interaction. Our experimental results are found to be in good quantitative
agreement with predictions of the spectral kinetic theory of soliton gas
despite the presence of perturbative higher-order effects that break the
integrability of the wave dynamics.
