the energy measurement, the HCAL is also able to perform a precise time measurement for each energy deposit. Precise time measurements are valuable for excluding calorimeter noise and energy deposits from beam halo and cosmic ray muons. Time information can also be valuable for identifying new physics signals such as long-lived particle decays and slow high-mass charged particles [@cite:cmsHSCPnote].

This paper is organized as follows. Section \[sec:HCALdesc\] reviews the pertinent details of the HCAL construction and their fundamental impact on timing resolution. Section \[sec:reco\] discusses the method used to extract a time value from the digitized HCAL signal. In Section \[sec:tbandsplash\], the validation of the method is presented based on measurements in test beam and initial beam operations of the LHC in September 2008. Section \[sec:suppression\] details the performance of timing filters in the suppression of non-collision-based backgrounds and the effect these timing filters have on simulated physics events.

CMS Hadron Calorimeter Description {#sec:HCALdesc}
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A detailed description of the HCAL can be found elsewhere [@cite:jinstcms]. Briefly, the HCAL consists of a set of sampling calorimeters. The barrel [@cite:epjcHB] and endcap [@cite:jinstcmsHE] calorimeters utilize alternating layers of brass as absorber and plastic scintillator as active material. The scintillation light is 