  We experimentally demonstrate orbiting of isotropic, dielectric
microparticles around an optical nanofiber that guides elliptically polarized
fundamental modes. The driving transverse radiation force appears in the
evanescent electromagnetic fields due to orbital angular momentum. The force
direction is opposite to that of the energy flow circulation around the
nanofiber. Our results verify the theoretically predicted negative optical
torque on a sufficiently large particle in the vicinity of a nanofiber.
