Experimental study of the rare decays K0L → μe, K0L → ee, K0L → μμ, and K0L → eeee

T. Akagi, R. Fukuhisa, Y. Hemmi, T. Inagaki, K. Ishikawa, T. Kishida, M. Kobayashi, T. K. Komatsubara, M. Kuze, F. Sai, T. Sato, T. Shinkawa, F. Suekane, K. Takamatsu, J. Toyoura, S. S. Yamamoto, Y. Yoshimura

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An experiment to search for the KL0→μe and KL0→ee decays and to measure the branching ratio of the KL0→μμ decay was performed at the KEK 12-GeV Proton Synchrotron. The single-event sensitivity of the present experiment for these channels was around 4×10-11. No event was observed in the fiducial region for the KL0→μe decay and one event, which could not be distinguished from the background, was observed in the fiducial region for the KL0→ee decay. The obtained upper limits on the branching ratios at 90% confidence level were B(KL0→μe)<9.4×10-11 and B(KL0→ee)<1.6×10-10. The branching ratio of the KL0→μμ decay was obtained to be [7.9±0.6 (stat ±0.2 (syst)]×10-9 based on 179 events in the fiducial region. Using 18 events with the effective mass Me+e->470 MeV /c2 in the e+e- sample for the KL0→ee decay search, the branching ratio of the KL0→e+e-e+e- decay was estimated to be [6±2 (stat) ±1 (syst)]×10-8 for Me+e->470 MeV/c2 and [7±3 (stat)±2(syst)]×10-8 for Me+e->480 MeV/c2.

Original languageEnglish
Pages (from-to)2061-2089
Number of pages29
JournalPhysical Review D
Issue number5
Publication statusPublished - 1995 Jan 1

ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)

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