The $jpsi$ $pt$ spectrum and nuclear modification factor ($raa$) are reported for $pt < 5 gevc$ and $|y|<1$ from 0% to 60% central Au+Au and Cu+Cu collisions at $snn = 200 gev$ at STAR. A significant suppression of $pt$-integrated $jpsi$ production is observed in central Au+Au events. The Cu+Cu data are consistent with no suppression, although the precision is limited by the available statistics. $raa$ in Au+Au collisions exhibits a strong suppression at low transverse momentum and gradually increases with $pt$. The data are compared to high-$pt$ STAR results and previously published BNL Relativistic Heavy Ion Collider results. Comparing with model calculations, it is found that the invariant yields at low $pt$ are significantly above hydrodynamic flow predictions but are consistent with models that include color screening and regeneration.
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