  We study a quasi-two-dimensional monolayer of granular rods fluidized by a
spatially and temporally homogeneous upflow of air. By tracking the position
and orientation of the particles, we characterize the dynamics of the system
with sufficient resolution to observe ballistic motion at the shortest time
scales. Particle anisotropy gives rise to dynamical anisotropy and
superdiffusive dynamics parallel to the rod's long axis, causing the parallel
and perpendicular mean squared displacements to become diffusive on different
timescales. The distributions of free times and free paths between collisions
deviate from exponential behavior, underscoring the non-thermal character of
the particle motion. The dynamics show evidence of rotational-translational
coupling similar to that of an anisotropic Brownian particle. We model
rotational-translation coupling in the single-particle dynamics with a modified
Langevin model using non-thermal noise sources. This suggests a
phenomenological approach to thinking about collections of self-propelling
particles in terms of enhanced memory effects.
