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First measurement of $φ$ meson production in 30 GeV proton-nucleus reactions via di-electron decay at J-PARC

J-PARC E16 collaboration, :, Satomi Nakasuga, Yuhei Morino, Kazuya Aoki, Yoki Aramaki, Daichi Arimizu, Sakiko Ashikaga, Wen-Chen Chang, Ren Ejima, Hideto En'yo, Dairon Rodriguez Garces, Johann M. Heuser, Ryotaro Honda, Masaya Ichikawa, Daichi Ishii, Shunsuke Kajikawa, Jo Kakunaga, Koki Kanno, Daisuke Kawama, Yusuke Komatsu, Takehito Kondo, Yusuke Hori, Hikari Murakami, Tomoki Murakami, Ryotaro Muto, Shunnosuke Nagafusa, Wataru Nakai, Megumi Naruki, Yuki Obara, Shuta Ochiai, Makoto Ogura, Kyoichiro Ozawa, Adrian Rodriguez Rodriguez, Hiroyuki Sako, Susumu Sato, Michiko Sekimoto, Kenta Shigaki, Kazuki Suzuki, Tomonori Takahashi, Tomohiro Taniguchi, Maksym Teklishyn, Alberica Toia, Rento Yamada, Kanako Yamaguchi, Yorito Yamaguchi, Shogo Yanai, Satoshi Yokkaichi

Abstract

We present the first measurement of the production of the $φ$ meson in 30 GeV proton-nucleus interactions on carbon and copper targets via the di-electron decay channel. The measurement was conducted at the high-momentum beamline of the J-PARC Hadron Experimental Facility, which was commissioned in 2020. The $e^+e^-$ pairs were detected using the E16 spectrometer, during a commissioning run of the J-PARC E16 experiment. The $φ$ mesons are successfully reconstructed on all experimental targets. The obtained yields are converted to the total production cross section, assuming a kinematical distribution of the event generator JAM. The total cross sections derived are 2.0 $\pm$ 0.9 (stat.) $\pm$ 1.0 (syst.) mb on the carbon target and 10.3 $\pm$ 4.4 (stat.) $\pm$ 4.4 (syst.) mb on the copper target. The mass-number dependence of the cross section is discussed using the parameter $α$, defined as $σ\propto A^α$, resulting in $α= $ 0.99 $\pm$ 0.38 (stat.) $\pm$ 0.34 (syst.). The extrapolation to $A=1$, which means that the cross section of proton-proton reactions, is in good agreement with the existing measurements at comparable energies.

First measurement of $φ$ meson production in 30 GeV proton-nucleus reactions via di-electron decay at J-PARC

Abstract

We present the first measurement of the production of the meson in 30 GeV proton-nucleus interactions on carbon and copper targets via the di-electron decay channel. The measurement was conducted at the high-momentum beamline of the J-PARC Hadron Experimental Facility, which was commissioned in 2020. The pairs were detected using the E16 spectrometer, during a commissioning run of the J-PARC E16 experiment. The mesons are successfully reconstructed on all experimental targets. The obtained yields are converted to the total production cross section, assuming a kinematical distribution of the event generator JAM. The total cross sections derived are 2.0 0.9 (stat.) 1.0 (syst.) mb on the carbon target and 10.3 4.4 (stat.) 4.4 (syst.) mb on the copper target. The mass-number dependence of the cross section is discussed using the parameter , defined as , resulting in 0.99 0.38 (stat.) 0.34 (syst.). The extrapolation to , which means that the cross section of proton-proton reactions, is in good agreement with the existing measurements at comparable energies.
Paper Structure (14 sections, 1 equation, 3 figures, 4 tables)

This paper contains 14 sections, 1 equation, 3 figures, 4 tables.

Table of Contents

  1. Introduction
  2. Experimental setup
  3. high-momentum beamline
  4. J-PARC E16 spectrometer
  5. Trigger and event selection
  6. Analysis
  7. Event reconstruction
  8. Efficiency evaluation
  9. The number of protons
  10. Result and Discussion
  11. Mass spectra
  12. Systematic uncertainties
  13. Total cross section
  14. Summary and Outlook

Figures (3)

  • Figure 1: a) Three-dimensional schematic view of the proposed E16 spectrometer in the spectrometer magnet (called 'FM magnet'). b) Cross-sectional view of the E16 spectrometer. The depicted eight detector modules are already constructed in the present data taking. c) Enlarged view of the experimental targets.
  • Figure 2: Invariant mass spectra on carbon and copper experimental targets.
  • Figure 3: Mass number dependence of the estimated total cross section. The filled black circles represent the results of the present measurement. The black bars indicate the statistical uncertainties, while the unfilled black boxes denote the systematic uncertainties of the total cross section. The linear extrapolation of these two data points is shown as a red dashed line. The results from measurements with the other energies are shown as a triangle and an inverted triangle. The orange star is explained in the text.