Speaker
Description
The COMET experiment aims to search for muon-to-electron conversion with an unprecendetedly high sensitivity. One of the severest backgrounds in the Phase-I experiment is originated from cosmic muons. In particular, part of the rear side of a detector solenoid magnet is difficult to be covered by veto counters. Cosmic muons sneak into the solenoid from the loophole, scattered and leaving a track in a cylindrical drift chamber. Among them, a positive muon track with reverse direction may mimic a signal electron with 105 MeV/c. In order to suppress the sneaking cosmic positive muon background, we developed a method to discriminate the track direction by using track fitting quality based on the GENFIT framework. We demonstrated that the positive muon background can be reduced by an order of magnitude. In this presentation, we will report the idea, demonstration, preliminary results, and prospects of further improvement.
