Photon-veto counters at the outer edge of the endcap calorimeter for the KOTO experiment

T. Matsumura, T. Shinkawa, H. Yokota, E. Iwai, T. K. Komatsubara, J. W. Lee, G. Y. Lim, J. Ma, T. Masuda, H. Nanjo, T. Nomura, Y. Odani, Y. D. Ri, K. Shiomi, Y. Sugiyama, S. Suzuki, M. Togawa, Y. Wah, H. Watanabe, T. Yamanaka

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)


The Outer-Edge Veto (OEV) counter subsystem for extra-photon detection from the backgrounds for the KL0→π0νν¯ decay is located at the outer edge of the endcap CsI calorimeter of the KOTO experiment at J-PARC. The subsystem is composed of 44 counters with different cross-sectional shapes. All counters are made of lead and scintillator plates and read out through wavelength-shifting fibers. In this paper, we discuss the design and performances of the OEV counters under heavy load (~8tons/m2) in vacuum. For 1-MeV energy deposit, the average light yield and time resolution are 20.9 photo-electrons and 1.5 ns, respectively. Although no pronounced peak by minimum-ionizing particles is observed in the energy distributions, an energy calibration method with cosmic rays works well in monitoring the gain stability with an accuracy of a few percent.

Original languageEnglish
Pages (from-to)19-31
Number of pages13
JournalNuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Publication statusPublished - Jul 10 2015
Externally publishedYes


  • Energy calibration
  • J-PARC
  • KOTO
  • Kaon rare decay
  • Lead-scintillator sandwich
  • WLS-fiber readout

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Instrumentation


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