positive and negative endcaps, will be studied with future “beam splash” data from both directions.

The results shown in the last two sections indicate that the methods of time reconstruction and synchronization are effective both in the H2 test beam environment and with the HCAL integrated in CMS. The final offline time corrections, which will be determined with collision data when they become available, are expected to provide synchronization with a spread in the per-channel mean times of less than 1 ns.

Impact of Timing in Analysis {#sec:suppression}
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Many interesting physics processes that the CMS experiment was designed to study or discover contain the signature of an undetected particle. Examples include the Standard Model neutrino and the lightest stable particle in several hypothetical supersymmetric particle spectra. Such particles would pass undetected through CMS, carrying some of the energy and momentum that would otherwise counterbalance the other collision products registered in the calorimeters. At hadron colliders, the initial energy and longitudinal momentum of the colliding hadronic constituents are not known, but the initial transverse momentum is known to be negligible in comparison and can be treated as zero. Therefore, the benchmark used to infer the existence of an unobserved particle 