  Using two-dimensional particle-in-cell simulations, we characterize the
energy spectra of particles accelerated by relativistic magnetic reconnection
(without guide field) in collisionless electron-positron plasmas, for a wide
range of upstream magnetizations $\sigma$ and system sizes $L$. The particle
spectra are well-represented by a power law $\gamma^{-\alpha}$, with a
combination of exponential and super-exponential high-energy cutoffs,
proportional to $\sigma$ and $L$, respectively. For large $L$ and $\sigma$, the
power-law index $\alpha$ approaches about 1.2.
