  We present a study of the average transverse momentum ($p_t$) fluctuations
and $p_t$ correlations for charged particles produced in Cu+Cu collisions at
midrapidity for $\sqrt{s_{NN}} =$ 62.4 and 200 GeV. These results are compared
with those published for Au+Au collisions at the same energies, to explore the
system size dependence. In addition to the collision energy and system size
dependence, the $p_t$ correlation results have been studied as functions of the
collision centralities, the ranges in $p_t$, the pseudorapidity $\eta$, and the
azimuthal angle $\phi$. The square root of the measured $p_t$ correlations when
scaled by mean $p_t$ is found to be independent of both colliding beam energy
and system size studied. Transport-based model calculations are found to have a
better quantitative agreement with the measurements compared to models which
incorporate only jetlike correlations.
