Present status of the search for the K$^{0}_{L} \rightarrow \pi^{0}\nu\bar{\nu}$ decay with the KOTO detector at J-PARC

TL;DR

This paper reports on the search for the rare decay K$^{0}_{L} ightarrow \pi^{0} uar{ u}$ using the KOTO detector at J-PARC, aiming to measure its branching ratio and probe for physics beyond the standard model.

Contribution

It presents the latest experimental efforts, detector improvements, and analysis status in searching for the decay, setting new upper limits closer to the standard model prediction.

Findings

Established an improved upper limit on the decay's branching ratio.

Enhanced detector performance and analysis techniques for rare decay detection.

Progressed towards sensitivity needed to observe the standard model predicted decay rate.

Abstract

We have performed a search for the K$^{0}_{L} \rightarrow \pi^{0}\nu\bar{\nu}$ decay with the KOTO detector at J-PARC. The KOTO detector was designed to observe the decay and measure its branching ratio (BR). Focusing on this golden decay in quark flavor physics provides an ideal candidate to probe for physics beyond the standard model (BSM). The established experimental upper limit of the branching ratio was set by the KEK E391a collaboration at 2.6 x 10$^{-8}$. This is still well above the standard model value of the branching ratio, which is predicted to be 2.43 x 10$^{-11}$ with minor uncertainties. The important signal is a pair of photons from the $\pi^{0}$ decay and no coincident signals from veto counters. This along with a large discernible transverse momentum provides us with unique signature. KOTO uses a Cesium Iodide (CsI) electromagnetic calorimeter as the main photon detector and hermetic veto counters to ensure that there are no other de- tected particles. This proceeding summarizes a presentation that discussed achievements, improvements to the detector, detailed the current analysis status for 2015 data, and future prospects.