Intercalibration of the CMS Electromagnetic Calorimeter with Neutral Pion Decays

In order to fully exploit the physics reach of the CMS experiment, it will be necessary to perform a precise in situ calibration of the CMS electromagnetic calorimeter. Achieving the design-goal calibration precision of 0.5% will be especially critical for a possible Higgs boson discovery in the two-photon decay channel. In this paper we evaluate the potential of a novel calibration technique that makes use of photon pairs produced in neutral pion decays. We show that 95% of the barrel electromagnetic calorimeter can be calibrated to at least 1% (0.5%) precision after several days (weeks) of data-taking in the luminosity scenario of L = 2∙10^(33) cm^(-2) s^(-1). Furthermore, this calibration technique has been successfully tested in the π^− test beam runs, where the obtained calibration precision of 1% was found to be in good agreement with the Monte Carlo predictions