Speaker
Description
The discovery of proton decay would provide evidence for Grand Unified Theories (GUTs), which aim to reformulate the fundamental structure of particle physics. In currently operating large-scale neutrino experiments, as well as those scheduled to begin operation in the near future, the search for proton decay is one of the central programs exploring physics beyond the Standard Model.
Among the decay modes predicted by GUTs, the channel ${\rm p}\rightarrow {\rm e}^{+}\pi^{0}$ is expected to have a relatively large branching ratio. In this mode, a precise understanding of the interactions between the produced neutral pion and nucleons inside the nucleus is essential for an accurate estimation of the proton decay signal detection efficiency.
In this study, we re-evaluated the impact of nuclear effects on proton decay events in oxygen nuclei in a water Cherenkov detector using the GiBUU model. In addition, by modeling the detector response of a typical water Cherenkov detector, we estimated not only the proton decay signal detection efficiency but also the atmospheric neutrino–induced background event rate within the GiBUU framework.
In contrast to commonly used neutrino event generators, employed in existing proton decay search studies, based on factorized primary interactions followed by cascade final-state interactions, the GiBUU model consistently describes the Fermi motion, mean-field potentials, final-state interactions, etc., within a unified theoretical framework. This enables a coherent treatment of both primary interactions and subsequent nuclear propagation.
In this poster, we present simulations of proton decay and atmospheric neutrino events based on GiBUU, together with estimates of detection efficiency and background event rates that incorporate event reconstruction effects in a water Cherenkov detector. We also discuss the projected sensitivity to proton decay searches in the Hyper-Kamiokande experimental configuration.
The content of this poster is also presented in arXiv:2602.23063.