Kaon Quenching Studies to Improve JUNO’s Sensitivity to Proton Decay

Baryon number violation is one of the proposed conditions to explain the observed matter-antimatter imbalance in our universe. Currently, the proton lower lifetime limit in the decay channel p→ K⁺ + ν̄ has been set by the Super-Kamiokande collaboration to be 5.9 · 10³³ years. The Jiangmen Underground Neutrino Observatory (JUNO) aims to exceed Super-Kamiokande’s lifetime limit within a few years of data taking. Cosmic muons and atmospheric neutrinos impose main backgrounds, which can be excluded primarily via the shape of the prompt scintillation signal. The presented event selection strategy results in an overall sensitivity for p → K⁺ν̄ of 9.6 · 10³³ years at 90 % C.L. based on a total exposure of 200 kton · years. JUNO's capability to contribute to the proton decay search depends on the experiment’s ability to identify the kaon. The total light emission as a function of energy for a given particle species is governed by a semi-empirical model using the so-called Birks’ factor~$kB$. The UniKaon setup was developed to determine the kaon’s quenching behavior at proton decay relevant energies. A prototype of the primary detector was successfully operated at a neutron beamtime at the LNL in Legnaro, Italy. First simulations have proven the vessel’s shape to significantly influence the detected spectra, motivating a full light propagation simulation. Meanwhile, gain calibrations of the photomultiplier tubes for high photon yields are ongoing to improve the accuracy of determining the photon collection.