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arXiv · 1409.8367

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
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Abstract

The Outer-Edge Veto (OEV) counter subsystem for extra-photon detection from the backgrounds for the? $K^0_L\rightarrowπ^0ν\barν$ 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 ($\sim8$ tons/m$^2$) 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.

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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. 2015-05-19. Photon-Veto Counters at the Outer Edge of the Endcap Calorimeter for the KOTO Experiment. https://doi.org/10.1016/j.nima.2015.05.036

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