  We measure acceleration statistics of neutrally buoyant spherical particles
with diameter 0.4 < d/eta <27 in intense turbulence (400< R_lambda <815). High
speed cameras image polystyrene tracer particles in a flow between
counter-rotating disks. The measurements of acceleration variance, <a^2>,
clearly resolve the transition from the tracer like behavior of small particles
to the much smaller accelerations of large particles. For d>5 eta, <a^2>
decreases with diameter as d^{-2/3} in agreement with inertial range scaling
arguments. A model relating <a^2> to the pressure structure functions matches
the transition from small to large particle behavior if the particles respond
to pressure differences over (1.7 +- 0.3) d. A model relating <a^2> to the
fluid acceleration averaged over the particle diameter predicts the transition
with no free parameters, but does not show clean inertial range scaling in the
size range studied. Consistent with earlier work, we find that the scaled
acceleration probability density function shows very little dependence on
particle size.
