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arXiv · 2504.19090

The Imaging Time-of-Propagation Detector at Belle II

Hulya Atmacan·Matt Belhorn·Yinghui Guan·Longke Li·Bilas Pal·Saurabh Sandilya·Alan Schwartz·Boqun Wang·Shun Watanuki·Matthew Andrew·Matthew Barrett·Martin Bessner·Thomas Browder·J. Bynes·J. Cercillieux·Shawn Dubey·Oskar Hartbrich·Chris Ketter·Brian Kirby·Shahab Kohani·D. Kotchetkov·Luca Macchiarulo·B. Macek·Kurtis Nishimura·H. Purwar·Z. Sang·V. Shebalin·S. Tripathy·Gary Varner·K. Yoshihara·T. Kohriki·X. Wang·S. P. Maharana·V. S. Vismaya·Gerard Visser·Alessandro Gaz·Stefano Lacaprara·R. Stroili·Ezio Torassa·Roberto Mussa·Umberto Tamponi·Peter Krizan·Samo Korpar·Tara Nanut·A. Novosel·Marko Petric·L. Rizzuto·Marko Staric·Lucien Cremaldi·David Sanders·Y. Adachi·Y. Arita·D. Furumura·S. Hara·T. Hayakawa·S. Hirose·Y. Horii·Toru Iijima·Kenji Inami·Y. Ito·Y. Kato·N. Kiribe·R. Koga·K. Kojima·A. Maeda·Y. Maeda·K. Maehara·R. Maeshima·Kodai Matsuoka·G. Muroyama·T. Nakano·R. Okubo·R. Okuto·R. Omori·S. Senga·K. Suzuki·H. Takeichi·N. Tsuzuki·T. Yonekura·R. Conrad·James Fast·Brian Fulsom·Jan Strube·Lynn Wood·I. Danko·T. Gu·N. Herring·N. K. Nisar·S. Roffe·Vladimir Savinov·E. Wang·Vishal Bhardwaj·Alyssa Loos·Milind Purohit·Carl Rosenfeld
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Abstract

We report on the construction, operation, and performance of the Time-of-Propagation detector with imaging used for the Belle II experiment running at the Super-KEKB $e^+e^-$ collider. This detector is located in the central barrel region and uses Cherenkov light to provide particle identification among hadrons. The Cherenkov light is radiated in highly polished bars of synthetic fused silica (quartz) and transported to the ends of the bars via total internal reflection. One bar end is instrumented with finely segmented micro-channel-plate photomultiplier tubes to record the light, while the other end has a mirror attached to reflect the photons back to the instrumented end. Both the propagation times and hit positions of the Cherenkov photons are measured; these depend on the Cherenkov angle and together provide good discrimination among charged pions, kaons, and protons with momenta up to around 4 GeV/$c$. To date, the detector has been used to record and analyze almost 600 fb$^{-1}$ of Belle II data.

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Hulya Atmacan, Matt Belhorn, Yinghui Guan, Longke Li, Bilas Pal, Saurabh Sandilya, Alan Schwartz, Boqun Wang, Shun Watanuki, Matthew Andrew, Matthew Barrett, Martin Bessner, Thomas Browder, J. Bynes, J. Cercillieux, Shawn Dubey, Oskar Hartbrich, Chris Ketter, Brian Kirby, Shahab Kohani, D. Kotchetkov, Luca Macchiarulo, B. Macek, Kurtis Nishimura, H. Purwar, Z. Sang, V. Shebalin, S. Tripathy, Gary Varner, K. Yoshihara, T. Kohriki, X. Wang, S. P. Maharana, V. S. Vismaya, Gerard Visser, Alessandro Gaz, Stefano Lacaprara, R. Stroili, Ezio Torassa, Roberto Mussa, Umberto Tamponi, Peter Krizan, Samo Korpar, Tara Nanut, A. Novosel, Marko Petric, L. Rizzuto, Marko Staric, Lucien Cremaldi, David Sanders, Y. Adachi, Y. Arita, D. Furumura, S. Hara, T. Hayakawa, S. Hirose, Y. Horii, Toru Iijima, Kenji Inami, Y. Ito, Y. Kato, N. Kiribe, R. Koga, K. Kojima, A. Maeda, Y. Maeda, K. Maehara, R. Maeshima, Kodai Matsuoka, G. Muroyama, T. Nakano, R. Okubo, R. Okuto, R. Omori, S. Senga, K. Suzuki, H. Takeichi, N. Tsuzuki, T. Yonekura, R. Conrad, James Fast, Brian Fulsom, Jan Strube, Lynn Wood, I. Danko, T. Gu, N. Herring, N. K. Nisar, S. Roffe, Vladimir Savinov, E. Wang, Vishal Bhardwaj, Alyssa Loos, Milind Purohit, Carl Rosenfeld. 2025-09-27. The Imaging Time-of-Propagation Detector at Belle II. https://doi.org/10.1016/j.nima.2025.170627

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