Increasing Acceptance in the KOTO Detector

The KOTO experiment is a collaboration involving the University of Chicago that intends to measure the branching ratio of the K L → πνν̄. This particular decay demonstrates direct CP violation; the Standard Model provides a theoretical value for the branching ratio. However, this value is also sensitive to physics beyond the Standard Model, such as supersymmetry. By accurately measuring this value, it is possible to test the Standard Model and search for evidence of physics beyond it. In order to accurately measure this value, it is important to measure a number of these rare decays. The current detector design only has an acceptance of 9.4%[1]; previous research has shown that by recording events incident on the side of the detector, the acceptance could be increased up to 77.3% [2]. However, these events may also veto themsevles, due to a secondary signal produced by the electromagnetic shower in the detector. A model was created of a photon incident on the side of the detector. It showed that events could indeed produce such a secondary signal; however, it also showed that this was dependant on the incident angle, and that many such events could be recouperated. Thus, this method would still provide a significant increase in acceptance for the KOTO detector.