  We use a computational model to investigate the emergence of interaction
forces between pairs of intruders in a horizontally vibrated granular fluid.
The time evolution of a pair of particles shows a maximum of the likelihood to
find the pair at contact in the direction of shaking. This relative interaction
is further studied by fixing the intruders in the simulation box where we
identify effective mechanical forces, and torques between particles and
quantify an emergent long range attractive force as a function of the shaking
relative angle, amplitude, and the packing density of grains. We determine the
local density and kinetic energy profiles of granular particles along the axis
of the dimer to find no gradients in the density fields and additive gradients
in the kinetic energies.
