of the location of the front-end electronics, tends to skew reconstructed times earlier for higher $\eta$, and this is the effect that dominates. The combination of these two effects induces a timing dependence on $\eta$, with a spread in each half-barrel of about 15 ns. Smaller variations as a function of $\phi$ are induced by clock distribution differences and other effects. By applying proper sampling delay settings, this spread can be reduced substantially. In addition, the reconstruction software utilizes a set of per-channel calibration constants to synchronize the mean timing of energy measurements to less than 1 ns.

Fiber lengths also differ within each calorimeter cell along the radial coordinate, but in this case there are no means available to compensate for these differences. Since the signals from all the scintillator layers comprising one cell are optically summed, and the optical path lengths are not equalized across the layers, the resulting signal is smeared in time. For hadrons, which exhibit large shower-to-shower fluctuations in longitudinal development, the optical summing of layers imposes a limit on the timing resolution, estimated to be approximately 1 ns. For signals with uniform energy deposit in each layer (such as those arising from the beam-collimator 