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論文

Evaluation of the performance of event reconstruction algorithms in the JSNS$$^2$$ experiment using a $$^{252}$$Cf calibration source

Lee, D. H.*; 百々 拓; 羽賀 勝洋; 原田 正英; 長谷川 勝一; 春日井 好己; 木下 秀孝; 増田 志歩; 明午 伸一郎; 酒井 健二; et al.

Nuclear Instruments and Methods in Physics Research A, 1072, p.170216_1 - 170216_6, 2025/03

https://doi.org/10.1016/j.nima.2025.170216
 被引用回数：2 パーセンタイル：98.29(Instruments & Instrumentation)

JSNS$$^2$$ investigates short-baseline neutrino oscillations using a 24-meter baseline and a 17-tonne Gd-loaded liquid scintillator target. Accurate event-reconstruction algorithms are crucial for analyzing experimental data. The algorithms undergo meticulous validation through calibration with a $$^{252}$$Cf source. This paper outlines the methodology and evaluates the reconstruction performance, focusing on neutrino interactions up to approximately 50 MeV for sterile neutrino searches. Both $$^{252}$$Cf and Michel electron events are studied to evaluate reconstruction accuracy. The analysis concludes that the uncertainty of the fiducial volume, with an appropriate correction, is much less than the requirement of JSNS$$^2$$ requirement (10%). Furthermore, the energy resolution is measured to be 3.3 $$pm$$ 0.1% for the Michel electron endpoint and 4.3 $$pm$$ 0.1% for the n-Gd peak in the central region.

論文

Pulse shape discrimination in JSNS$$^2$$

百々 拓; 羽賀 勝洋; 原田 正英; 長谷川 勝一; 春日井 好己; 木下 秀孝; 増田 志歩; 明午 伸一郎; 酒井 健二; 鈴谷 賢太郎; et al.

Progress of Theoretical and Experimental Physics (Internet), 2025(2), p.023H02_1 - 023H02_8, 2025/02

https://doi.org/10.1093/ptep/ptaf016
 被引用回数：0 パーセンタイル：0.00(Physics, Multidisciplinary)

JSNS$$^2$$ (J-PARC Sterile Neutrino Search a t J-PARC Spallation Neutron Source) is an experiment that is searching for sterile neutrinos via the observation of $$bar{nu}_{mu} to bar{nu}_e$$ appearance oscillations using neutrinos from muon decay-at-rest. For this search, rejecting cosmic-ray-induced neutron events by Pulse Shape Discrimination (PSD) is essential because the JSNS$$^2$$ detector is located above ground, on the third floor of the building. We have achieved 94.95$$% pm 0.15%$$ rejection of neutron events while keeping 92.82$$% pm 1.77%$$ of signal, electron-like events using a data-driven likelihood method. This article will report the PSD technique using the full fiducial volume of the JSNS$$^2$$ detector.

論文

First measurement of missing energy due to nuclear effects in monoenergetic neutrino charged-current interactions

Marzec, E.*; 百々 拓; 羽賀 勝洋; 原田 正英; 長谷川 勝一; 春日井 好己; 木下 秀孝; 増田 志歩; 明午 伸一郎; 酒井 健二; et al.

Physical Review Letters, 134, p.081801_1 - 081801_9, 2025/00

https://doi.org/10.1103/PhysRevLett.134.081801
 被引用回数：1 パーセンタイル：0.00(Physics, Multidisciplinary)

We present the first measurement of the missing energy due to nuclear effects in monoenergetic, muon neutrino charged-current interactions on carbon, originating from $$K^+ to mu^+ nu_{mu}$$ decay at rest ($$E_{nu_{mu}} = 235.5 MeV$$), performed with the J-PARC Sterile Neutrino Search at the J-PARC Spallation Neutron Source liquid scintillator based experiment. Toward characterizing the neutrino interaction, ostensibly $$nu_{mu}n to mu^- p$$ or $$nu_{mu}$$ $$^{12}$$C $$to$$ $$mu^-$$ $$^{12}$$N, we define the missing energy as the energy transferred to the nucleus ($$omega$$) minus the kinetic energy of the outgoing proton(s), $$E_m equiv omega - Sigma T_p$$, and relate this to visible energy in the detector, $$E_m = E_{nu_{mu}} (235.5 MeV) - m_{mu}(105.7 MeV) + [m_n - m_p(1.3 MeV)] - E_{vis}$$. The missing energy, which is naively expected to be zero in the absence of nuclear effects (e.g., nucleon separation energy, Fermi momenta, and final-state interactions), is uniquely sensitive to many aspects of the interaction, and has previously been inaccessible with neutrinos. The shape-only, differential cross section measurement reported, based on a $$(77pm 3%)$$ pure double-coincidence kaon decay-at-rest signal (621 total events), provides detailed insight into neutrino-nucleus interactions, allowing even the nuclear orbital shell of the struck nucleon to be inferred. The measurement provides an important benchmark for models and event generators at hundreds of MeV neutrino energies, characterized by the difficult-to-model transition region between neutrino-nucleus and neutrino-nucleon scattering, and relevant for applications in nuclear physics, neutrino oscillation measurements, and Type-II supernova studies.

論文

Missing-mass measurement of the $$^{12}$$C$$(K^-,K^+)$$ reaction at 1.8 GeV/$$c$$ with the Superconducting Kaon spectrometer

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

Progress of Theoretical and Experimental Physics (Internet), 2024(9), p.091D01_1 - 091D01_13, 2024/09

https://doi.org/10.1093/ptep/ptae133
 被引用回数：0 パーセンタイル：0.00(Physics, Multidisciplinary)

We conducted a measurement of the inclusive missing-mass spectrum in the $$^{12}$$C$$(K^-, K^+)$$ reaction at an incident beam momentum of 1.8 GeV/$$c$$. This measurement was carried out utilizing the Superconducting Kaon Spectrometer (SKS) and the K1.8 beamline spectrometer at the Hadron Experimental Hall in J-PARC. Remarkably, our experimental setup yielded an exceptionaly good energy resolution of 8.2 MeV (FWHM), enabling us to observe significant enhancements in the vicinity of the $$^{12}_{Xi}$$Be threshold region. In order to estimate the spectrum information, we employed several fitting parameters assumptions. The best agreement with the spectrum shape was obtained with combining quasi-free (QF) component and two-Gaussian functions, with the experimental resolution $$sigma$$ being held constant. The peak positions were obtained to be $$B_{Xi} = 8.9 pm 1.4$$ (stat.) $$^{+3.8}_{-3.1}$$ (syst.) MeV and $$B_{Xi} = -2.4 pm 1.3$$ (stat.) $$^{+2.8}_{-1.2}$$ (syst.) MeV. Another model assumption, utilizing quasi-free (QF) and one Breit-Wigner function with $$B_{Xi} = -2.7 pm 2.2$$ (stat.) $$^{+0.5}_{-0.7}$$ (syst.) MeV and $$Gamma = 4.1 pm 2.1$$ (stat.) $$^{+1.2}_{-0.7}$$ (syst.) MeV, also yielded a similar $$chi^2$$ value.

論文

Study on the accidental background of the JSNS$$^2$$ experiment

Lee, D. H.*; 百々 拓; 羽賀 勝洋; 原田 正英; 長谷川 勝一; 春日井 好己; 木下 秀孝; 増田 志歩; 明午 伸一郎; 酒井 健二; et al.

European Physical Journal C, 84, p.409_1 - 409_6, 2024/04

https://doi.org/10.1140/epjc/s10052-024-12778-7
 被引用回数：1 パーセンタイル：35.96(Physics, Particles & Fields)

JSNS$$^2$$ (J-PARC Sterile Neutrino Search at J-PARC Spallation Neutron Source) is an experiment that searches for sterile neutrinos via the observation of $$bar{nu}_{mu} to bar{nu}_{e}$$ appearance oscillations using muon decay-at-rest neutrinos. The JSNS$$^2$$ experiment performed data taking from 2021. In this manuscript, a study of the accidental background is presented. The rate of the accidental background is (9.29$${pm}$$0.39)$${times}$$10$$^{-8}$$ / spill with 0.75 MW beam power and comparable to the expected number of signal events.

論文

The Acrylic vessel for JSNS$$^2$$-II neutrino target

Shin, C. D.*; 百々 拓; 羽賀 勝洋; 原田 正英; 長谷川 勝一; 春日井 好己; 木下 秀孝; 増田 志歩; 明午 伸一郎; 酒井 健二; et al.

Journal of Instrumentation (Internet), 18(12), p.T12001_1 - T12001_9, 2023/12

https://doi.org/10.1088/1748-0221/18/12/T12001
 被引用回数：0 パーセンタイル：0.00(Instruments & Instrumentation)

The JSNS$$^2$$ (J-PARC Sterile Neutrino Search at J-PARC Spallation Neutron Source) is an experiment designed for the search for sterile neutrinos. The experiment is currently at the stage of the second phase named JSNS$$^2$$-II with two detectors at near and far locations from the neutrino source. One of the key components of the experiment is an acrylic vessel, that is used for the target volume for the detection of the anti-neutrinos. The specifications, design, and measured properties of the acrylic vessel are described.

論文

Superconducting dipole magnet for Hyperon spectrometer

Ahn, J. K.*; 長谷川 勝一; 今井 憲一*; 佐甲 博之; 佐藤 進; 谷田 聖; 他10名*

Nuclear Instruments and Methods in Physics Research A, 1047, p.167775_1 - 167775_13, 2023/02

https://doi.org/10.1016/j.nima.2022.167775
 被引用回数：1 パーセンタイル：17.31(Instruments & Instrumentation)

We have constructed a conduction-cooled superconducting dipole magnet for the Hyperon spectrometer at Japan Proton Accelerator Research Complex (J-PARC). The magnet is a Helmholtz-type dipole magnet with two circular coils with a radius of 500 mm separated by 500 mm. It provides a uniform magnetic field of 1.0 T or higher in a volume of $$phi600$$ mm $$times$$ 600 mm, covering the drift region of a time projection chamber (TPC). Owing to the target location inside the TPC, the Hyperon spectrometer has a broad angular coverage with a nearly $$2pi$$ solid angle. We have successfully excited the magnet up to 1.3 T. At 1.0 T, we operated it stably for more than 1 week in single-magnet configuration and double-magnet configuration with a normal-conducting 0.7-T dipole magnet located 30 cm apart. The measured magnetic field distribution in the TPC volume is consistent with the calculated field map.

論文

$$Xi^-$$ 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
 被引用回数：1 パーセンタイル：15.48(Physics, Multidisciplinary)

$$Xi^-$$ atomic X-ray spectroscopy is one of the most useful methods for investigation of the $$Xi$$-nucleus strong interaction. Since the X-ray energy is shifted and/or broadened due to the $$Xi$$-nucleus strong interaction compared to those calculated from electromagnetic interaction alone, the measurement of the energy shift, $$Delta$$E, and the width, $$Gamma$$, give us information on the $$Xi$$-nucleus potential. A serious problem in the measurement is the significant background derived from in-flight $$Xi^-$$ decay. A novel method of identifying stopped $$Xi^-$$ events using the nuclear emulsion was developed to realize the first $$Xi^-$$ atomic X-ray spectroscopy experiment as the J-PARC E07 experiment, which also aimed at searching for $$LambdaLambda$$ and $$Xi^-$$ hypernuclei in the emulsion. The X-rays emitted from $$Xi^-$$ Br and $$Xi^-$$ 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.

論文

Recent progress and future prospects of hyperon nucleon scattering experiment

三輪 浩司*; 藤田 真奈美; 原田 健志; 長谷川 勝一; 細見 健二; 市川 真也; 今井 憲一*; 佐甲 博之; 佐藤 進; 田村 裕和; et al.

EPJ Web of Conferences, 271, p.04001_1 - 04001_7, 2022/11

https://doi.org/10.1051/epjconf/202227104001

A new hyperon-proton scattering experiment, dubbed J-PARC E40, was performed to measure differential cross sections of the $$Sigma^+ p$$, $$Sigma^- p$$ elastic scatterings and the $$Sigma^- p to Lambda n$$ scattering by identifying a lot of $$Sigma $$ particles in the momentum ranging from 0.4 to 0.8 GeV/$$c$$ produced by the $$pi^{pm}p to K^+Sigma^{pm}$$ reactions. We successfully measured the differential cross sections of these three channels with a drastically improved accuracy with a fine angular step. These new data will become important experimental constraints to improve the theories of the two-body baryon-baryon interactions. Following this success, we proposed a new experiment to measure the differential cross sections and spin observables by using a highly polarized $$Lambda$$ beam for providing quantitative information on the $$Lambda N$$ interaction. The results of three $$Sigma p$$ channels and future prospects of the $$Lambda p$$ scattering experiment are described.

論文

Strangeness physics programs by S-2S at J-PARC

後神 利志*; 江端 健悟; 藤田 真奈美; 原田 健志; 長谷川 勝一; 細見 健二; 市川 裕大; 今井 憲一*; Kim, S.; 七村 拓野; et al.

EPJ Web of Conferences, 271, p.11002_1 - 11002_7, 2022/11

https://doi.org/10.1051/epjconf/202227111002

In the K1.8 beam-line at Hadron Experimental Facility of J-PARC, a new magnetic spectrometer S-2S is being installed. S-2S was designed to achieve a high momentum resolution of $$Delta p/p = 6 times 10^{-4}$$ in FWHM. Several strangeness-physics programs which require the high resolution will be realized by S-2S. The present article introduces J-PARC E70 (missing-mass spectroscopy of $$_{Xi}^{12}$$Be) and E94 (missing-mass spectroscopy of $$_{Lambda}^7$$Li, $$_{Lambda}^{10}$$B, and $$_{Lambda}^{12}$$C) experiments.

論文

Measurement of differential cross sections for $$Sigma^+ p$$ 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
 被引用回数：16 パーセンタイル：83.97(Physics, Multidisciplinary)

We performed a novel $$Sigma^+p$$ scattering experiment at the J-PARC Hadron Experimental Facility. Approximately 2400 $$Sigma^+p$$ elastic scattering events were identified from $$4.9 times 10^7$$ tagged $$Sigma^+$$ particles in the $$Sigma^+$$ momentum range 0.44 - 0.80 GeV/c. The differential cross sections of the $$Sigma^+p$$ 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 $$^3S_1$$ and $$^1P_1$$ 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 $$20^circ<|delta_{^3S_1}|<35^circ$$. If the sign of $$delta_{^3S_1}$$ is assumed to be negative, the interaction in this channel is moderately repulsive, as the Nijmegen extended-sort-core models predicted.

報告書

HTTR-熱利用試験専門委員会資料集

青木 健; 清水 厚志; 飯垣 和彦; 沖田 将一朗; 長谷川 武史; 水田 直紀; 佐藤 博之; 坂場 成昭

JAEA-Review 2022-016, 193 Pages, 2022/08

JAEA-Review-2022-016.pdf:42.06MB

日本原子力研究開発機構では、高温ガス炉による大量かつ安価なカーボンフリー水素製造技術の実用化を目指し、世界最高の原子炉出口冷却材温度950$$^{circ}$$Cを記録した高温工学試験研究炉(HTTR)を用いて水素製造を行うHTTR-熱利用試験を計画している。HTTR-熱利用試験では、原子力規制委員会からの設置許可取得を通じて、高温ガス炉と水素製造施設の接続に関し、高い安全性を実現する安全設計を確立することが求められている。しかしながら、これまでに原子炉に水素製造施設を接続した例は世界にまだなく、我が国唯一の高温ガス炉であるHTTRを含め、既存の原子力施設を対象とした安全設計ではこのようなシステムを想定していない。そこで、高温ガス炉研究開発センターの下に設置した「HTTR-熱利用試験専門委員会」では、原子力規制委員会による新規制基準への適合性審査に合格したHTTR安全設計をベースに、施設の変更や水素製造施設の接続に伴い安全設計上新たに考慮すべき事象に対する対策を考慮し、HTTR-熱利用試験施設の安全設計案の検討を行った。本稿は、HTTR-熱利用試験専門委員会の技術報告資料や委員コメントとその回答、議事録を取りまとめた。

報告書

HTTR-熱利用試験施設の安全設計の考え方

青木 健; 清水 厚志; 飯垣 和彦; 沖田 将一朗; 長谷川 武史; 水田 直紀; 佐藤 博之; 坂場 成昭

JAEA-Technology 2022-011, 60 Pages, 2022/07

JAEA-Technology-2022-011.pdf:2.08MB

日本原子力研究開発機構では、高温ガス炉による大量かつ安価なカーボンフリー水素製造技術の実用化を目指し、世界最高の原子炉出口冷却材温度950$$^{circ}$$Cを達成した高温工学試験研究炉(HTTR)を用いて水素製造を行うHTTR-熱利用試験を計画している。HTTR-熱利用試験では、原子力規制委員会からの設置変更許可取得を通じて、高温ガス炉と水素製造施設の接続に関し、高い安全性を実現する安全設計を確立することが求められている。そこで、HTTR安全設計をベースに、施設の変更や水素製造施設の接続に伴い安全設計上新たに考慮すべき事象に対する対策を考慮し、HTTR-熱利用試験施設の安全設計の考え方を検討した。検討に当たっては、原子炉安全の観点からの十分な安全性を確保することを大前提としつつ、水素製造施設に対して、高圧ガス災害に対する安全確保の多くの実績を有する一般産業法規を適用することを基本方針とした。本報では、水素製造施設への高圧ガス保安法適用に係る合理性や条件、HTTR-熱利用試験施設の安全機能の重要度分類や耐震設計上の重要度分類、重要安全施設の選定、原子炉設置変更許可申請に係る安全設計の考え方に関する検討結果を報告する。

論文

$$phi$$ meson production in $$p$$$$+$$Al, $$p$$$$+$$Au, $$d$$$$+$$Au, and $$^3$$He$$+$$Au collisions at $$sqrt{s_{_{NN}}}=200$$ GeV

Acharya, U. A.*; 長谷川 勝一; 今井 憲一*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他365名*

Physical Review C, 106(1), p.014908_1 - 014908_13, 2022/07

https://doi.org/10.1103/PhysRevC.106.014908
 被引用回数：6 パーセンタイル：65.93(Physics, Nuclear)

Small nuclear collisions are mainly sensitive to cold-nuclear-matter effects; however, the collective behavior observed in these collisions shows a hint of hot-nuclear-matter effects. The identified-particle spectra, especially the $$phi$$ mesons which contain strange and antistrange quarks and have a relatively small hadronic-interaction cross section, are a good tool to study these effects. The PHENIX experiment has measured $$phi$$ mesons in a specific set of small collision systems $$p$$$$+$$Al, $$p$$$$+$$Au, and $$^3$$He$$+$$Au, as well as $$d$$$$+$$Au, at $$sqrt{s_{_{NN}}}=200$$ GeV. The transverse-momentum spectra and nuclear-modification factors are presented and compared to theoretical-model predictions. The comparisons with different calculations suggest that quark-gluon plasma may be formed in these small collision systems at $$sqrt{s_{_{NN}}}=200$$ GeV. However, the volume and the lifetime of the produced medium may be insufficient for observing strangeness-enhancement and jet-quenching effects. Comparison with calculations suggests that the main production mechanisms of $$phi$$ mesons at midrapidity may be different in $$p$$$$+$$Al versus $$p/d/$$$$^3$$He$$+$$Au collisions at $$sqrt{s_{_{NN}}}=200$$ GeV. While thermal quark recombination seems to dominate in $$p/d/$$$$^3$$He$$+$$Au collisions, fragmentation seems to be the main production mechanism in $$p$$$$+$$Al collisions.

論文

Measurement of $$psi(2S)$$ nuclear modification at backward and forward rapidity in $$p$$$$+$$$$p$$, $$p$$$$+$$Al, and $$p$$$$+$$Au collisions at $$sqrt{s_{_{NN}}}=200$$ GeV

Acharya, U. A.*; 長谷川 勝一; 今井 憲一*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他310名*

Physical Review C, 105(6), p.064912_1 - 064912_15, 2022/06

https://doi.org/10.1103/PhysRevC.105.064912
 被引用回数：17 パーセンタイル：90.60(Physics, Nuclear)

Suppression of the $$J/psi$$ nuclear-modification factor has been seen as a trademark signature of final-state effects in large collision systems for decades. In small systems, the nuclear modification was attributed to cold-nuclear-matter effects until the observation of strong differential suppression of the $$psi(2S)$$ state in $$p/d$$$$+$$$$A$$ collisions suggested the presence of final-state effects. Results of $$J/psi$$ and $$psi(2S)$$ measurements in the dimuon decay channel are presented here for $$p$$$$+$$$$p$$, $$p$$$$+$$Al, and $$p$$$$+$$Au collision systems at $$sqrt{s_{_{NN}}}=200$$ GeV. The results are predominantly shown in the form of the nuclear-modification factor, $$R_{pA}$$, the ratio of the $$psi(2S)$$ invariant yield per nucleon-nucleon collision in collisions of proton on target nucleus to that in $$p$$$$+$$$$p$$ collisions. Measurements of the $$J/psi$$ and $$psi(2S)$$ nuclear-modification factor are compared with shadowing and transport-model predictions, as well as to complementary measurements at Large-Hadron-Collider energies.

論文

Systematic study of nuclear effects in $$p$$$$+$$Al, $$p$$$$+$$Au, $$d$$$$+$$Au, and $$^{3}$$He$$+$$Au collisions at $$sqrt{s_{_{NN}}}=200$$ GeV using $$pi^0$$ production

Acharya, U. A.*; 長谷川 勝一; 今井 憲一*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他547名*

Physical Review C, 105(6), p.064902_1 - 064902_19, 2022/06

https://doi.org/10.1103/PhysRevC.105.064902
 被引用回数：20 パーセンタイル：94.22(Physics, Nuclear)

The PHENIX collaboration presents a systematic study of $$pi^0$$ production from $$p$$$$+$$$$p$$, $$p$$$$+$$Al, $$p$$$$+$$Au, $$d$$$$+$$Au, and $$^{3}$$He$$+$$Au collisions at $$sqrt{s_{_{NN}}}=200$$ GeV. Measurements were performed with different centrality selections as well as the total inelastic, 0% - 100%, selection for all collision systems. For 0% - 100% collisions, the nuclear modification factors, $$R_{xA}$$, are consistent with unity for $$p_T$$ above 8 GeV/$$c$$, but exhibit an enhancement in peripheral collisions and a suppression in central collisions. The enhancement and suppression characteristics are similar for all systems for the same centrality class. It is shown that for high-$$p_T$$-$$pi^0$$ production, the nucleons in the $$d$$ and $$^3$$He interact mostly independently with the Au nucleus and that the counter intuitive centrality dependence is likely due to a physical correlation between multiplicity and the presence of a hard scattering process. These observations disfavor models where parton energy loss has a significant contribution to nuclear modifications in small systems. Nuclear modifications at lower $$p_T$$ resemble the Cronin effect - an increase followed by a peak in central or inelastic collisions and a plateau in peripheral collisions. The peak height has a characteristic ordering by system size as $$p$$$$+$$Au $$>$$ $$d$$$$+$$Au $$>$$ $$^{3}$$He$$+$$Au $$>$$ $$p$$$$+$$Al. For collisions with Au ions, current calculations based on initial state cold nuclear matter effects result in the opposite order, suggesting the presence of other contributions to nuclear modifications, in particular at lower $$p_T$$.

論文

Kinematic dependence of azimuthal anisotropies in $$p$$$$+$$Au, $$d$$$$+$$Au, and $$^3$$He+Au at $$sqrt{s_{_{NN}}}$$ = 200 GeV

Acharya, U. A.*; 長谷川 勝一; 今井 憲一*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他378名*

Physical Review C, 105(2), p.024901_1 - 024901_13, 2022/02

https://doi.org/10.1103/PhysRevC.105.024901
 被引用回数：13 パーセンタイル：86.23(Physics, Nuclear)

There is strong evidence for the formation of small droplets of quark-gluon plasma in $$p/d/^{3}$$He+Au collisions at the Relativistic Heavy Ion Collider (RHIC) and in $$p$$+$$p$$/Pb collisions at the Large Hadron Collider. In particular, the analysis of data at RHIC for different geometries obtained by varying the projectile size and shape has proven insightful. In the present analysis, we find excellent agreement with the previously published PHENIX at RHIC results on elliptical and triangular flow with an independent analysis via the two-particle correlation method, which has quite different systematic uncertainties and an independent code base. In addition, the results are extended to other detector combinations with different kinematic (pseudorapidity) coverage. These results provide additional constraints on contributions from nonflow and longitudinal decorrelations.

論文

Transverse single spin asymmetries of forward neutrons in $$p$$$$+$$$$p$$, $$p$$$$+$$Al, and $$p$$$$+$$Au collisions at $$sqrt{s_{_{NN}}}$$ = 200 GeV as a function of transverse and longitudinal momenta

Acharya, U. A.*; 長谷川 勝一; 今井 憲一*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他305名*

Physical Review D, 105(3), p.032004_1 - 032004_13, 2022/02

https://doi.org/10.1103/PhysRevD.105.032004
 被引用回数：4 パーセンタイル：36.52(Astronomy & Astrophysics)

In 2015 the PHENIX collaboration at the Relativistic Heavy Ion Collider recorded $$p$$$$+$$$$p$$, $$p$$$$+$$Al, and $$p$$$$+$$Au collision data at center of mass energies of $$sqrt{s_{_{NN}}}=200$$ GeV with the proton beam(s) transversely polarized. At very forward rapidities $$eta > 6.8$$ relative to the polarized proton beam, neutrons were detected either inclusively or in (anti)correlation with detector activity related to hard collisions. The resulting single spin asymmetries, that were previously reported, have now been extracted as a function of the transverse momentum of the neutron as well as its longitudinal momentum fraction $$x_F$$. The explicit kinematic dependence, combined with the correlation information allows for a closer look at the interplay of different mechanisms suggested to describe these asymmetries, such as hadronic interactions or electromagnetic interactions in ultra-peripheral collisions, UPC. Events that are correlated with a hard collision indeed display a mostly negative asymmetry that increases in magnitude as a function of transverse momentum with only little dependence on $$x_F$$. In contrast, events that are not likely to have emerged from a hard collision display positive asymmetries for the nuclear collisions with a kinematic dependence that resembles that of a UPC based model. Because the UPC interaction depends strongly on the charge of the nucleus, those effects are very small for $$p$$$$+$$$$p$$ collisions, moderate for $$p$$$$+$$Al collisions, and large for $$p$$$$+$$Au collisions.

論文

Transverse-single-spin asymmetries of charged pions at midrapidity in transversely polarized $$p{+}p$$ collisions at $$sqrt{s}=200$$ GeV

Acharya, U. A.*; 長谷川 勝一; 今井 憲一*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他306名*

Physical Review D, 105(3), p.032003_1 - 032003_8, 2022/02

https://doi.org/10.1103/PhysRevD.105.032003
 被引用回数：2 パーセンタイル：19.58(Astronomy & Astrophysics)

In 2015, the PHENIX collaboration has measured single-spin asymmetries for charged pions in transversely polarized proton-proton collisions at the center of mass energy of $$sqrt{s}=200$$ GeV. The pions were detected at central rapidities of $$|eta| < 0.35$$. The single-spin asymmetries are consistent with zero for each charge individually, as well as consistent with the previously published neutral-pion asymmetries in the same rapidity range. However, they show a slight indication of charge-dependent differences which may suggest a flavor dependence in the underlying mechanisms that create these asymmetries.

論文

Precise measurement of differential cross sections of the $${Sigma}^- p to {Lambda} n$$ reaction in momentum range 470-650 MeV/$$c$$

三輪 浩司*; 藤田 真奈美; 長谷川 勝一; 細見 健二; 市川 裕大*; 今井 憲一*; 七村 拓野; 佐甲 博之; 佐藤 進; 田村 裕和; et al.

Physical Review Letters, 128(7), p.072501_1 - 072501_6, 2022/02

https://doi.org/10.1103/PhysRevLett.128.072501
 被引用回数：19 パーセンタイル：86.28(Physics, Multidisciplinary)

The differential cross sections of the $${Sigma}^- p to {Lambda} n$$ reaction were measured accurately for the $${Sigma}^-$$ momentum $$(p_{{Sigma}})$$ ranging from 470 to 650 MeV/$$c$$ at the J-PARC Hadron Experimental Facility. Precise angular information about the $${Sigma}^- p to {Lambda} n$$ reaction was obtained for the first time by detecting approximately 100 reaction events at each angular step of $${Delta}cos{theta} = 0.1$$. The obtained differential cross sections show slightly forward-peaking structure in the measured momentum regions. The cross sections integrated for $$-0.7 < cos{theta} < 1.0$$ were obtained as $$22.5 pm 0.68 (stat.) pm 0.65 (syst.)$$ mb and $$15.8 pm 0.83(stat.) pm 0.52 (syst.)$$ mb for $$470 < p_{{Sigma}}$$ (MeV/c) $$<550$$ and $$550 < p_{{Sigma}}$$ (MeV/c)$$<650$$, respectively. These results show a drastic improvement compared to past measurements of the hyperon-proton scattering experiments. They will play essential roles in updating the theoretical models of the baryon-baryon interactions.

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