Search for dinucleon decay into kaons in Super-Kamiokande

Area of Science:

• Particle Physics
• Nuclear Physics
• Experimental Physics

Background:

• Proton decay searches probe fundamental symmetries and new physics beyond the Standard Model.
• R-parity violating (RPV) supersymmetry offers potential explanations for observed phenomena, including proton decay modes.

Purpose of the Study:

• To search for the dinucleon decay mode pp → K+ K+.
• To constrain the R-parity violating parameter λ112'' using experimental data.
• To establish limits on the partial lifetime of proton decay.

Main Methods:

• Analysis of 91.6 kton·yr of data collected by the Super-Kamiokande-I detector.
• Application of a boosted decision tree (BDT) algorithm to identify signal events.
• Estimation of background from atmospheric neutrino interactions and signal detection efficiency.

Main Results:

• No candidate events for the pp → K+ K+ decay were observed in the dataset.
• The expected background from atmospheric neutrinos was calculated to be 0.28±0.19 events.
• A signal detection efficiency of 12.6%±3.2% was estimated.

Conclusions:

• A lower limit of 1.7×10^32 years was set on the partial lifetime for the decay O16 → C14K+ K+ at 90% confidence level.
• An upper limit of 7.8×10^-9 was placed on the R-parity violating parameter λ112''.