Commissioning of the electron identification system for Dilepton measurement in pA collisions at J-PARC

• Published in: Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment Vol. 1041; p. 167335
• Main Authors: Nakasuga, Satomi, Aoki, Kazuya, Aramaki, Yoki, Arimizu, Daichi, Ashikaga, Sakiko, Ebata, Kengo, Honda, Ryotaro, Ichikawa, Masaya, Kajikawa, Shunsuke, Kanno, Koki, Kimura, Yuta, Kondo, Takehito, Kyan, Shono, Morino, Yuhei, Murakami, Hikari, Murakami, Tomoki, Nakai, Wataru, Naruki, Megumi, Nonaka, Toshihiro, Noumi, Hiroyuki, Ogata, Naoki, Ozawa, Kyoichiro, Sako, Hiroyuki, Sato, Susumu, Sekimoto, Michiko, Shirotori, Kotaro, Takahashi, Tomonori, Takaura, Yudai, Tatsumi, Ryohei, Tsukui, Kosuke, Yahiro, Kanta, Yokkaichi, Satoshi
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 11.10.2022
• Subjects: Cherenkov detector; Di-electron decay; GEM; Hadron blind detector; Lead-glass; Cherenkov detector; Di-electron decay; Hadron blind detector; Lead-glass; GEM
• ISSN: 0168-9002; 1872-9576
• DOI: 10.1016/j.nima.2022.167335

Hadron mass spectra are expected to be modified in nuclear matter due to a partial restoration of chiral symmetry. We perform the J-PARC E16 experiment to measure the spectral modification of vector mesons in nuclei. We detect electron-positron pairs from decays of ϕ mesons, produced in 30 GeV pA reactions. It is a key for our experiment to separate electrons from huge hadronic backgrounds. To identify electrons, we developed two-stage detectors comprising hadron blind detectors (HBDs) and lead-glass electromagnetic calorimeters (LGs). These detectors were constructed and installed at the J-PARC high-momentum beamline in 2020, and commissioning runs were performed in 2020 and 2021. The HBDs and the LGs were stably operated at a high counting rate generated in 10-MHz pA interaction at targets, and successfully detected electrons. In the preliminary results, the pion rejection powers were found to be 97.6 ± 0.6% and 91.2 ± 0.7% for the HBD and LG, respectively, which are consistent with the design performance, at the operation thresholds. Further evaluation of electron efficiency is ongoing.