Monte Carlo simulations of secondary cosmic-ray variations in atmospheric electric fields; Implications for long duration electron and gamma-ray emissions from thunderclouds

土屋 晴文

Progress of Theoretical and Experimental Physics (Internet), 2026(4), p.043F01_1 - 043F01_23, 2026/04

https://doi.org/10.1093/ptep/ptag040

Monte Carlo simulations were conducted using the Particle and Heavy Ion Transport code System (PHITS) to investigate the role of secondary cosmic rays in the generation of long-duration bursts from thunderclouds and to clarify the conditions of the electric field region responsible for particle acceleration. The simulations utilized realistic secondary cosmic-ray spectra, including gamma rays, electrons, positrons, and muons, as input. The simulation results indicate that gamma rays provide the dominant supply of seed electrons for long-duration bursts, regardless of the geometry or strength of the electric field region. They also reveal the structure and strength of the electric field region required to produce gamma rays exceeding several tens of MeV, which have so far been detected only by high-altitude observations. Furthermore, the fluxes of long-duration bursts estimated from the simulation results were compared with observational data to constrain the properties of the electric field region. In particular, the comparison with measurements at Yangbajing, located at an altitude of 4.3 km, helps narrow down the possible range of electric field strengths and configurations.

Longitudinal phase-space direct measurement of intermediate pulses for a high-intensity beam accumulation in the J-PARC RCS

守屋 克洋; 原田 寛之

Progress of Theoretical and Experimental Physics (Internet), 2025(11), p.113G01_1 - 113G01_14, 2025/11

https://doi.org/10.1093/ptep/ptaf146

The Japan Proton Accelerator Research Complex (J-PARC) 3-GeV rapid cycling synchrotron (RCS) accumulates a MW-class high-intensity proton beam. The RCS adopts a phase-space painting injection in both transverse and longitudinal planes during the multi-turn injection to mitigate space charge force, which is a source of beam loss. In longitudinal painting injection, it is important to maintain the momentum of all pulsed beams injected from the Linac. However, the momentum from the Linac fluctuates due to beam loading induced by the high-intensity beam. The RCS requires a thinned time structure of the pulsed beam during injection to control the charge density of the accumulated beam. The momentum fluctuation increases as a result of the complicated time structure. In this study, we developed and evaluated a direct measurement system for the longitudinal phase space (phase and momentum deviation) of all injected pulsed beams. Furthermore, the phase space under various operating conditions was measured, and an increase in momentum fluctuations due to beam loading under thinned beam conditions was clearly observed. This monitoring system is well suited for facilities accelerating beams with complex time structures, and it can significantly contribute to beam loss reduction.

Analysis of spectral modification of mesons at finite density using a transport approach in the 12 GeV pA reactions

市川 真也; Gubler, P.; 成木 恵; KEK-PS E325 Collaboration*; 他25名*

Progress of Theoretical and Experimental Physics (Internet), 2025(9), p.093D01_1 - 093D01_21, 2025/08

https://doi.org/10.1093/ptep/ptaf108

The hadron spectrum at finite density is an important observable for exploring the origin of hadron masses. In the KEK-PS E325 experiment, the di-electron decays of mesons inside and outside nuclei were measured using 12 GeV pA reactions. In the previous analysis, a significant excess was observed on the low-mass side of the meson peak in the data for slow-moving mesons ( = / 1.25) with the Cu target, and in-medium vector meson spectral modification was verified. We newly employed the PHSD transport approach to take into account the time evolution of spatial density distribution of the target nuclei. Consistent with the previous analysis, a significant excess was observed in the present analysis as well. It was found that incorporating momentum dependence into the spectral modification leads to better agreement with the experimental results. For the slow-moving mesons with the Cu target, the newly obtained modification parameters are consistent with those from the previous analysis within the uncertainties.

Half-integer random resonance compensation for further beam power ramp-up in the 3-GeV rapid cycling synchrotron of the Japan Proton Accelerator Research Complex

小島 邦洸; 原田 寛之; 田村 文彦; 沖田 英史; 地村 幹; Saha, P. K.

Progress of Theoretical and Experimental Physics (Internet), 2025(1), p.013G01_1 - 013G01_19, 2025/01

https://doi.org/10.1093/ptep/ptae185

本研究は、3GeVシンクロトロン(Rapid cycling synchrotron: RCS)のビーム大強度・高品質化に貢献するものである。大強度の陽子シンクロトロンにおいて、ビーム損失は深刻な装置の放射化をもたらし、ビーム出力の制限に繋がる。そのため、RCSの大強度ビーム安定化には、ビーム損失の更なる低減が不可欠である。特に、加速器のビームを制御する電磁石の配置とビームが進行方向に垂直な方向に行う振動の周期が一定の関係(共鳴条件)を満たすとき、共鳴現象により多大なビーム損失が起きる。この共鳴の発生を避けるため、ビームの振動の周期は共鳴条件を避けるよう慎重に制御されている。一方で、ビーム大強度化に伴って粒子間のクーロン斥力の影響によって個々の粒子の振動数は個別の影響を受け変化するため、共鳴条件はビーム密度に依存した幅を持つようになる。これにより、ビームの振動の周期を制御することによる共鳴条件の回避が難しくなる。RCSではビーム強度が一定以上に達した場合に、半整数共鳴を避けることが困難となるため、これがRCSの最大出力を制限している。そこで、本研究では補正磁場の重畳による半整数共鳴の影響の低減(補正)を試みた。ビーム試験と数値計算の活用により、RCS設計出力と同等な強度を持つビーム条件において、半整数共鳴に起因するビーム損失を1/3にまで低減する補正状況を達成した。本論文では、一連のビーム試験結果に加えて、共鳴補正手法の詳細について報告する。

Production cross-sections of residual nuclides from Zr + at 27 MeV/nucleon

Hwang, J.*; Chillery, T.*; 堂園 昌伯*; 今井 伸明*; 道正 新一郎*; 炭竃 聡之*; 千賀 信幸*; 大田 晋輔*; 中山 梓介; 他49名*

Progress of Theoretical and Experimental Physics (Internet), 2024(9), p.093D03_1 - 093D03_12, 2024/09

https://doi.org/10.1093/ptep/ptae139

核変換は高レベル廃棄物の再処理、特に使用済み燃料からZrのような長寿命核種を処理するための有望な手段であると考えられている。これらの核種に対する核反応データを蓄積することは、核変換の検討や反応機構を包括的に理解するために不可欠である。本研究では、Zrに対する陽子入射反応からの残留核生成断面積を、核子当たり27MeVのエネルギーで逆運動学法を用いて測定した。理研RIBFのOEDOビームラインを用いて、Nb, Zr, Yの各同位体の生成断面積を導出した。励起関数について、TALYSやCCONEによる理論予測は、本研究や先行研究の実験値と概ね良い一致を示した。本研究で測定された断面積は、廃棄物処理に関する将来の検討のための貴重なデータとなる。

Development of a single-ended magnetic alloy loaded cavity in the Japan Proton Accelerator Research Complex rapid cycling synchrotron

山本 昌亘; 野村 昌弘; 沖田 英史; 島田 太平; 田村 文彦; 原 圭吾*; 長谷川 豪志*; 大森 千広*; 杉山 泰之*; 吉井 正人*

Progress of Theoretical and Experimental Physics (Internet), 2023(7), p.073G01_1 - 073G01_16, 2023/07

https://doi.org/10.1093/ptep/ptad085

J-PARC 3GeVシンクロトロンでは、ビームの加速に金属磁性体を装荷した加速空胴を使用している。金属磁性体の広帯域特性を利用して、ビームを加速する周波数だけでなく、その高調波も増幅する多重高調波励振によってビームの安定加速を実現している。既設の空胴は真空管増幅器において、加速電場を発生させる絶縁ギャップの前後に個別に電圧を印加するプッシュプル励振となるよう設計されている。プッシュプル励振は、ビームを加速しない状態では高調波歪みを抑制でき、さらに空胴の長さを短くできる利点がある。しかし、大強度ビーム加速時にはビームが誘起する電圧によって多重高調波励振が歪められ、それを補正するために絶縁ギャップの前後にかかる陽極電圧振幅が深刻な不平衡を引き起こし、真空管の動作を制限してしまう。現状では、設計値である1MWビーム加速は達成できているが、より安定な運転を行う上では真空管の不平衡が問題となる。この問題を避けるため、シングルエンド励振の空胴を開発した。シングルエンド励振は本質的に不平衡が起こらず、さらに既設の空胴に対して遥かに少ない電力消費を達成できることが分かった。

Inverse mass ordering of light scalar mesons in the Nambu-Jona-Lasinio model

西園寺 貴公*; 慈道 大介*; 原田 正康*

Progress of Theoretical and Experimental Physics (Internet), 2023(3), p.033D01_1 - 033D01_18, 2023/03

https://doi.org/10.1093/ptep/ptad028

The masses of the low-lying scalar mesons are investigated in the three-flavor Nambu-Jona-Lasinio (NJL) model by treating the scalar mesons as composite objects of a quark and an antiquark. It is known that a simple picture fails to reproduce the so-called inverse mass ordering for the scalar mesons. Recently a new mechanism to reproduce the observed mass spectrum of the scalar mesons was proposed in a linear sigma model by introducing flavor symmetry breaking induced by the U(1) axial anomaly. Motivated by this proposal, we examine whether this new mechanism also works in the NJL model. By calculating the scalar meson masses, we find that the NJL model reproduces the observed mass ordering with sufficient strength of the new term. With this mechanism, it turns out that the constituent strange quark mass becomes degenerate to that of the up and down quarks if the inverse mass ordering is reproduced. We also discuss the scalar diquark masses to check the consistency of the degeneracy of the constituent quark masses with the light baryon masses.

atomic X-ray spectroscopy using a counter-emulsion hybrid method

藤田 真奈美; 長谷川 勝一; 細見 健二; 市川 真也; 市川 裕大; Kim, S.; 七村 拓野; 佐甲 博之; 田村 裕和; 山本 剛史; et al.

Progress of Theoretical and Experimental Physics (Internet), 2022(12), p.123D01_1 - 123D01_17, 2022/12

https://doi.org/10.1093/ptep/ptac156

atomic X-ray spectroscopy is one of the most useful methods for investigation of the -nucleus strong interaction. Since the X-ray energy is shifted and/or broadened due to the -nucleus strong interaction compared to those calculated from electromagnetic interaction alone, the measurement of the energy shift, E, and the width, , give us information on the -nucleus potential. A serious problem in the measurement is the significant background derived from in-flight decay. A novel method of identifying stopped events using the nuclear emulsion was developed to realize the first atomic X-ray spectroscopy experiment as the J-PARC E07 experiment, which also aimed at searching for and hypernuclei in the emulsion. The X-rays emitted from Br and Ag atoms were measured using germanium detectors. No clear peaks were observed in the obtained spectra. However, we succeeded in reducing the background to 1/170 by this method employing coincidence measurements using nuclear emulsion and X-ray detectors.

Measurement of differential cross sections for elastic scattering in the momentum range 0.44-0.80 GeV/c

七村 拓野; 藤田 真奈美; 長谷川 勝一; 市川 真也; 市川 裕大; 今井 憲一*; 成木 恵; 佐藤 進; 佐甲 博之; 田村 裕和; et al.

Progress of Theoretical and Experimental Physics (Internet), 2022(9), p.093D01_1 - 093D01_35, 2022/09

https://doi.org/10.1093/ptep/ptac101

We performed a novel scattering experiment at the J-PARC Hadron Experimental Facility. Approximately 2400 elastic scattering events were identified from tagged particles in the momentum range 0.44 - 0.80 GeV/c. The differential cross sections of the elastic scattering were derived with much better precision than in previous experiments. The obtained differential cross sections were approximately 2 mb/sr or less, which were not as large as those predicted by the fss2 and FSS models based on the quark cluster model in the short-range region. By performing phase-shift analyses for the obtained differential cross sections, we experimentally derived the phase shifts of the and channels for the first time. The phase shift of the 3S1 channel, where a large repulsive core was predicted owing to the Pauli effect between quarks, was evaluated to be . If the sign of is assumed to be negative, the interaction in this channel is moderately repulsive, as the Nijmegen extended-sort-core models predicted.

Two-dimensional resistive-wall impedance with finite thickness; Its mathematical structures and their physical meanings

菖蒲田 義博

Progress of Theoretical and Experimental Physics (Internet), 2022(5), p.053G01_1 - 053G01_44, 2022/05

AA2021-0891.pdf:2.09MB

https://doi.org/10.1093/ptep/ptac053

相対論的ビームが、抵抗性のチャンバーを通過する場合を考える。この時、ビームは抵抗性インピーダンスをチャンバーに誘起するが、スキンデプスがチャンバー厚より大きい場合、インピーダンスは周波数に比例して減少する。この現象は一般に電磁場がチャンバーから漏れていると解釈される。しかし、古典的な抵抗性インピーダンスの式では、スキンデプスがチャンバー厚を超えたときに壁電流が漏れ場に変換される様子を動的に表現できていないため、チャンバー上の壁電流とチャンバーからの漏れ場の関係が不明である。そこで、抵抗性インピーダンスを並列回路モデルで表現し直しなすことで、この現象に動的なイメージを提供している教科書もあるが、この式にはいくつかの欠点がある。本研究では、基礎的な立場からそれらの式を見直し、相対論的ビームに対する抵抗性インピーダンスについて、より適切で厳密な物理描像を与えることを試みた。加えて、非相対論的ビームに対する縦方向インピーダンスと横方向抵抗インピーダンスについても見直しをおこなった。