Effect of Zero Suppression on Cosmic Ray Muon Energy Spectra in HCAL

In order to reduce event size during LHC running, it will be necessary to suppress readout of HCAL channels with energy below certain threshold. However, Zero Suppression (ZS) introduces bias to reconstructed energy in HCAL. In this note we evaluate and quantify effect of ZS (with firmware version 5A) on distribution of reconstructed energy deposition of cosmic ray muons. We conclude that cosmic ray data must be taken without zero suppression in order to have an unbiased sample, which can used to validate the HCAL energy calibration and to evaluate the effect of different possible options for zero suppression on HCAL calibration, muon ID and muon isolation algorithms.