Beam performance and data-constrained optical modeling of a UV-transmitting acrylic Cherenkov counter for hadron identification
Abstract
A threshold Cherenkov counter based on ultraviolet-transmitting (UVT) acrylic has been developed for hadron identification in the S-2S spectrometer at J-PARC. Three 730 mm × 100 mm × 50 mm radiators were beam tested: polished UVT acrylic without WLS, UVT acrylic roughened on the four long surfaces without WLS, and polished UVT acrylic containing 10 ppm by mass bis-MSB as a wavelength shifter (WLS). The polished/WLS prototype gave the largest two-ended photoelectron yield among the tested configurations. At a 1-photoelectron software-SUM threshold, its measured detection efficiency remained above 99% throughout the scanned longitudinal range, with no significant degradation up to an average extracted-particle rate of approximately 2.5×105 s−1 during beam delivery. Beam observables constrained a Geant4 optical model with one common detector response scale and no PMT-specific response tuning. The model reproduces the observed response hierarchy and main longitudinal trends. In the central |y| < 200 mm region, simulated and measured MPV estimators for the calibration configurations typically agree within about 15%, while larger deviations occur toward the radiator ends, especially for rough/no-WLS. With the calibrated parameters fixed, the model was used to compare unmeasured detector configurations and quantify the momentum dependence of K+/p discrimination. In the central, normal incidence geometry, a 90% K+-survival working point is predicted to keep proton survival below 3% up to about 1.8 GeV/c. The measurements and constrained extrapolations support the polished UVT/WLS configuration for S-2S and quantify its expected particle-identification reach beyond the simple threshold regime.
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BibTeX
@misc{gogami2026beam,
title = {{Beam performance and data-constrained optical modeling of a UV-transmitting acrylic Cherenkov counter for hadron identification}},
author = {Toshiyuki Gogami and Tomohiro Taniguchi and Daigo Watanabe and Jung Keun Ahn and Elena Botta and Kengo Ebata and Alessandro Feliciello and Hiroyuki Fujioka and Manami Fujita and Takeshi Harada and Shuhei Hayakawa and Yuning Hong and Yudai Ichikawa and Ryo Imamoto and Kei Ishido and Saya Iwai and Teppei Iwamoto and Koji Miwa and Tomofumi Nagae and Takuya Nanamura and Ruri Sasaki and Chesu Seong and Shun Shibata and Shuji Takahashi and Hirokazu Tamura and Kiyoshi Tanida and Kotaro Tsutsumi and Mifuyu Ukai and Takeshi Yamamoto},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.34712},
eprint = {2610.34712},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.34712},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - UNPB
TI - Beam performance and data-constrained optical modeling of a UV-transmitting acrylic Cherenkov counter for hadron identification
AU - Toshiyuki Gogami
AU - Tomohiro Taniguchi
AU - Daigo Watanabe
AU - Jung Keun Ahn
AU - Elena Botta
AU - Kengo Ebata
AU - Alessandro Feliciello
AU - Hiroyuki Fujioka
AU - Manami Fujita
AU - Takeshi Harada
AU - Shuhei Hayakawa
AU - Yuning Hong
AU - Yudai Ichikawa
AU - Ryo Imamoto
AU - Kei Ishido
AU - Saya Iwai
AU - Teppei Iwamoto
AU - Koji Miwa
AU - Tomofumi Nagae
AU - Takuya Nanamura
AU - Ruri Sasaki
AU - Chesu Seong
AU - Shun Shibata
AU - Shuji Takahashi
AU - Hirokazu Tamura
AU - Kiyoshi Tanida
AU - Kotaro Tsutsumi
AU - Mifuyu Ukai
AU - Takeshi Yamamoto
PY - 2026
DA - 2026/10/26
PB - arXiv
DO - 10.48550/arxiv.2610.34712
UR - https://arxiv.org/abs/2610.34712
AB - A threshold Cherenkov counter based on ultraviolet-transmitting (UVT) acrylic has been developed for hadron identification in the S-2S spectrometer at J-PARC. Three 730 mm × 100 mm × 50 mm radiators were beam tested: polished UVT acrylic without WLS, UVT acrylic roughened on the four long surfaces without WLS, and polished UVT acrylic containing 10 ppm by mass bis-MSB as a wavelength shifter (WLS). The polished/WLS prototype gave the largest two-ended photoelectron yield among the tested configurations. At a 1-photoelectron software-SUM threshold, its measured detection efficiency remained above 99% throughout the scanned longitudinal range, with no significant degradation up to an average extracted-particle rate of approximately 2.5×10^5 s^−1 during beam delivery. Beam observables constrained a Geant4 optical model with one common detector response scale and no PMT-specific response tuning. The model reproduces the observed response hierarchy and main longitudinal trends. In the central |y| < 200 mm region, simulated and measured MPV estimators for the calibration configurations typically agree within about 15%, while larger deviations occur toward the radiator ends, especially for rough/no-WLS. With the calibrated parameters fixed, the model was used to compare unmeasured detector configurations and quantify the momentum dependence of K^+/p discrimination. In the central, normal incidence geometry, a 90% K^+-survival working point is predicted to keep proton survival below 3% up to about 1.8 GeV/c. The measurements and constrained extrapolations support the polished UVT/WLS configuration for S-2S and quantify its expected particle-identification reach beyond the simple threshold regime.
ER -