Study of the K_L⁰ → K_S⁰ Regeneration Process with the KOTO Detector

The KOTO experiment at the J-PARC research facility in Tokai, Japan is designed to measure the branching ratio of a neutral kaon (K_L ⁰) decaying into a neutral pion and two neutrinos. This decay is extremely rare with the Standard Model (SM) predicted branching ratio to be less than 1 per 30 billion. Due to the rarity of this decay and the experimental difficulty, it has yet to be observed. Measuring the branching ratio is one of the best methods to probe for additional contributions to CP violation. An experimental branching ratio measurement will either confirm SM predictions or point towards new physics.

As this process is very rare, a clear understanding of possible background sources is crucial. Thus, we need to be able to distinguish the decay of interest among all other events. A potential background source can originate from K_L⁰ to K_S⁰ regeneration. This presentation will discuss the methods and results of the cross section measurement of the coherent regeneration of the K_L⁰ into the K_S⁰ on an aluminum target with the KOTO detector.