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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：0 パーセンタイル：0.01(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

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：6 パーセンタイル：74.91(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

Measurement of the differential cross sections of the $$Sigma^- p$$ elastic scattering in momentum range 470 to 850 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; 成木 恵; 佐甲 博之; 佐藤 進; et al.

Physical Review C, 104(4), p.045204_1 - 045204_20, 2021/10

https://doi.org/10.1103/PhysRevC.104.045204
 被引用回数：13 パーセンタイル：89.06(Physics, Nuclear)

A high statistics $$Sigma p$$ scattering experiment is performed at the J-PARC Hadron Experimental Facility. Momentum-tagged $$Sigma^-$$s running in a liquid hydrogen target are accumulated by detecting the reaction with a high intensity $$pi^-$$ beam of 20 M/spill. The differential cross sections of the $$Sigma^- p$$ elastic scattering were derived with a drastically improved accuracy by identifying approximately 4,500 events from 1.72 $$times$$ 10$$^7$$ $$Sigma^-$$. The derived differential cross section shows a clear forward-peaking angular distribution for a $$Sigma^-$$ momentum range from 470 to 850 MeV/$$c$$. The accurate data will impose a strong constraint on the theoretical models of the baryon-baryon interactions.

論文

Probing gluon spin-momentum correlations in transversely polarized protons through midrapidity isolated direct photons in $$p^uparrow+p$$ 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 Letters, 127(16), p.162001_1 - 162001_8, 2021/10

https://doi.org/10.1103/PhysRevLett.127.162001
 被引用回数：8 パーセンタイル：67.41(Physics, Multidisciplinary)

Studying spin-momentum correlations in hadronic collisions offers a glimpse into a three-dimensional picture of proton structure. The transverse single-spin asymmetry for midrapidity isolated direct photons in $$p^uparrow+p$$ collisions at $$sqrt{s}$$=200 GeV is measured with the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC). Because direct photons in particular are produced from the hard scattering and do not interact via the strong force, this measurement is a clean probe of initial-state spin-momentum correlations inside the proton and is in particular sensitive to gluon interference effects within the proton. This is the first time direct photons have been used as a probe of spin-momentum correlations at RHIC. The uncertainties on the results are a fifty-fold improvement with respect to those of the one prior measurement for the same observable, from the Fermilab E704 experiment. These results constrain gluon spin-momentum correlations in transversely polarized protons.

論文

Establishment of a modern experimental technique of a $$Sigma p$$ scattering experiment at J-PARC

赤澤 雄也*; 藤田 真奈美; 長谷川 勝一; 細見 健二; 市川 真也; 市川 裕大; 今井 憲一*; 七村 拓野; 成木 恵; 佐甲 博之; et al.

JPS Conference Proceedings (Internet), 33, p.011134_1 - 011134_6, 2021/03

https://doi.org/10.7566/JPSCP.33.011134

We are performing a scattering experiment between a $$Sigma$$ hyperon and a proton (J-PARC E40) at the K1.8 beamline in the J-PARC Hadron Hall. The purpose of this experiment is to investigate the $$Sigma N$$ interaction by measuring the differential cross sections of the $$Sigma^+ p$$, $$Sigma^- p$$ elastic scatterings and $$Sigma^- p to Lambda n$$ inelastic scattering. The experimental data gives a strong constraint on the theoretical models of the $$Sigma N$$ interaction. The identification of $$Sigma p$$ scattering event with a high statistics is important by overcoming the difficulties in the hyperon proton scattering experiment. We have introduced a new identification method of the $$Sigma p$$ scattering event, which does not need to detect $$Sigma$$ particles directly. We used a new detector system called CATCH and two spectrometer systems installed at the upstream and the downstream of a liquid hydrogen target. A high intensity $$pi$$ beam of 20 M/spill was used to produce $$Sigma$$ particle. The momenta of $$pi$$ beam and scattered $$K^+$$ were measured by the spectrometers to reconstruct the momentum of a $$Sigma$$ beam produced via the $$pi p to Sigma K^+$$ reactions. The scattering angle and the kinetic energy of recoil protons from the $$Sigma p$$ scattering were measured by CATCH for the identification of the $$Sigma p$$ scattering events by checking the kinematic consistency. A part of the experiment was performed in 2018 and 2019 in J-PARC. As a result of analyzing the collected data, the $$Sigma^-$$ production and the $$Sigma^- p$$ scattering reaction have been identified. It means that our new measurement and analysis method are successfully working well. Analysis for deriving the differential cross section of the $$Sigma p$$ scattering is on going.

論文

Measurement of displacement cross section for proton in the kinetic energy range from 0.4 GeV to 3 GeV

明午 伸一郎; 松田 洋樹; 岩元 洋介; 吉田 誠*; 長谷川 勝一; 前川 藤夫; 岩元 大樹; 中本 建志*; 石田 卓*; 牧村 俊助*

JPS Conference Proceedings (Internet), 33, p.011050_1 - 011050_6, 2021/03

https://doi.org/10.7566/JPSCP.33.011050

加速器駆動型核変換システム(ADS)では、加速器の真空領域と標的領域の隔壁となるビーム入射窓の開発が重要となる。ビーム窓の損傷評価には、原子当たりの弾き出し数(DPA)が用いられるが、DPAの導出に用いられる弾き出し断面積の実験データは20MeV以上のエネルギー領域の陽子に対しほとんどないため、ADSにおいて重要な0.4$$sim$$3GeV陽子における弾き出し断面積の測定を開始した。弾き出し断面積は、損傷を維持するため極低温に冷却された試料の陽子入射に伴う抵抗率変化を陽子フルエンスとフランケル対当たりの抵抗率変化で除することにより導出できる。実験はJ-PARCセンターの3GeV陽子シンクロトロン施設で行い、アルミ及び銅を試料として用いた。実験で得られた断面積と一般的に弾き出し断面積の計算に使用されるNRTモデルの計算との比較の結果、NRTモデルの計算は実験を約3倍過大評価することが判明した。

論文

Study of $$Lambda$$ identification method by the $$pi^-p to K^0Lambda$$ reaction for a $$Lambda p$$ scattering experiment at J-PARC

坂尾 珠和*; 藤田 真奈美; 長谷川 勝一; 細見 健二; 市川 真也; 市川 裕大; 今井 憲一*; 七村 拓野; 成木 恵; 佐甲 博之; et al.

JPS Conference Proceedings (Internet), 33, p.011133_1 - 011133_6, 2021/03

https://doi.org/10.7566/JPSCP.33.011133

The $$pi^-p to K^0Lambda$$ reaction is an important elementary process to produce $$Lambda$$ from a proton target and is a key for a $$Lambda p$$ scattering experiment where the momentum of $$Lambda$$ should be tagged from the missing momentum of the $$(pi^-,K^0)$$ reaction. However, the $$(pi^-,K^0)$$ spectroscopy method has not been established yet due to the difficulty of the $$K^0$$ detection. Therefore, we have proposed a new $$K^0$$ detection method where $$pi^+$$ and $$pi^-$$ from the $$K^0$$ decay are measured by a forward magnetic spectrometer and a detector cluster surrounding the target, respectively. The feasibility of the $$K^0$$ detection method was confirmed by analyzing the J-PARC E40 data taken with such a detector system. In the analysis, $$Lambda$$'s were successfully identified in the missing mass spectrum of the $$pi^-p to K^0 X$$ reaction.

論文

J-PARC E07; Systematic study of double strangeness system with hybrid emulsion method

吉田 純也; 赤石 貴也; 藤田 真奈美; 長谷川 勝一; 橋本 直; 細見 健二; 市川 真也; 市川 裕大; 今井 憲一*; Kim, S.; et al.

JPS Conference Proceedings (Internet), 33, p.011112_1 - 011112_8, 2021/03

https://doi.org/10.7566/JPSCP.33.011112

J-PARC E07 is the most ambitious and complex emulsion experiment to date investigating double hypernuclei with Hybrid emulsion method. The physics run at the K1.8 beam line in the J-PARC hadron experimental facility have been completed in 2017. The emulsion sheets are presently being analyzed with dedicated optical microscopes. Current statistics are estimated to be more 3 times than that of previous experiments. Quantitative data on the $$Lambda Lambda$$ and $$Xi N$$ interaction are being accumulated successfully via analysis of double $$Lambda$$ and $$Xi$$ hypernuclei. Multiple $$Xi$$ hypernucleus candidates suggests several features about $$Xi$$ hypernucleus that the identification efficiency of $$^{15}_Xi$$C is significantly higher than other mode, many daughters of $$^{15}_Xi$$C are identified as He or Be, and multiple bound states of $$Xi^-$$ exist in the $$^{14}$$N nucleus. An analysis of X-ray spectroscopy of $$Xi^-$$ hyperatoms are ongoing.

論文

Transverse single-spin asymmetries of midrapidity $$pi^0$$ and $$eta$$ mesons in 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309名*

Physical Review D, 103(5), p.052009_1 - 052009_10, 2021/03

https://doi.org/10.1103/PhysRevD.103.052009
 被引用回数：5 パーセンタイル：42.69(Astronomy & Astrophysics)

We present a measurement of the transverse single-spin asymmetry for $$pi^0$$ and $$eta$$ mesons in $$p^uparrow$$$$+$$$$p$$ collisions in the pseudorapidity range $$|eta|< 0.35$$ and at a center-of-mass energy of 200 GeV with the PHENIX detector at the Relativistic Heavy Ion Collider. In comparison with previous measurements in this kinematic region, these results have a factor of 3 smaller uncertainties. As hadrons, $$pi^0$$ and $$eta$$ mesons are sensitive to both initial- and final-state nonperturbative effects for a mix of parton flavors. Comparisons of the differences in their transverse single-spin asymmetries have the potential to disentangle the possible effects of strangeness, isospin, or mass. These results can constrain the twist-3 trigluon collinear correlation function as well as the gluon Sivers function.

論文

Transverse momentum dependent forward neutron single spin asymmetries 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308名*

Physical Review D, 103(3), p.032007_1 - 032007_8, 2021/02

https://doi.org/10.1103/PhysRevD.103.032007
 被引用回数：2 パーセンタイル：19.06(Astronomy & Astrophysics)

In 2015, the PHENIX collaboration has measured very forward ($$eta > 6.8$$) single-spin asymmetries of inclusive neutrons in transversely polarized proton-proton and proton-nucleus collisions at a center of mass energy of 200 GeV. A previous publication from this data set concentrated on the nuclear dependence of such asymmetries. In this measurement the explicit transverse-momentum dependence of inclusive neutron single spin asymmetries for proton-proton collisions is extracted using a bootstrapping-unfolding technique on the transverse momenta. This explicit transverse-momentum dependence will help improve the understanding of the mechanisms that create these asymmetries.

論文

Observation of Coulomb-assisted nuclear bound state of $$Xi^-$$-$$^{14}$$N system

早川 修平; 藤田 真奈美; 長谷川 勝一; 橋本 直; 細見 健二; 市川 裕大; 今井 憲一*; 七村 拓野; 成木 恵; 佐甲 博之; et al.

Physical Review Letters, 126(6), p.062501_1 - 062501_6, 2021/02

https://doi.org/10.1103/PhysRevLett.126.062501
 被引用回数：34 パーセンタイル：94.71(Physics, Multidisciplinary)

In an emulsion-counter hybrid experiment performed at J-PARC, a $$Xi^-$$ absorption event was observed which decayed into twin single-$$Lambda$$ hypernuclei. Kinematic calculations enabled a unique identification of the reaction process as $$Xi^{-} + ^{14}$$N$$ rightarrow ^{10}_Lambda$$Be + $$^5_Lambda$$He. For the binding energy of the $$Xi^{-}$$ hyperon in the $$Xi^-$$-$$^{14}$$N system a value of $$1.27 pm 0.21$$ MeV was deduced. The energy level of $$Xi^-$$ is likely a nuclear $$1p$$ state which indicates a weak $${Xi}N$$-$$LambdaLambda$$ coupling.

論文

Study of $$Sigma N$$ interaction from the $$Sigma p$$ scattering experiment at J-PARC

三輪 浩司*; 藤田 真奈美; 長谷川 勝一; 細見 健二; 市川 真也; 市川 裕大; 今井 憲一*; 七村 拓野; 成木 恵; 佐甲 博之; et al.

Journal of Physics; Conference Series, 1643, p.012174_1 - 012174_6, 2020/12

https://doi.org/10.1088/1742-6596/1643/1/012174
 被引用回数：2 パーセンタイル：83.94(Astronomy & Astrophysics)

A high statistics $$Sigma p$$ scattering experiment has been performed at the K1.8 beamline in the J-PARC Hadron Experimental Facility. Data for momentum-tagged $$Sigma^-$$ beam running in a liquid hydrogen target were accumulated by detecting the $$pi^{-}p to {K}^{+}{Sigma}^{-}$$ reaction with a high intensity $$pi^-$$ beam of 20 M/spill. The number of the $$Sigma^-$$ beam was about $$1.7 times 10^7$$ in total. The $$Sigma^- p$$ elastic scattering and the $$Sigma^- p to Lambda n$$ inelastic scattering events were successfully observed with about 100 times larger statistics than that in past experiments.

論文

Study on the baryon interaction by $$Xi$$ hypernuclear spectroscopy with the $$(K^-, K^+)$$ reaction

後神 利志*; 藤田 真奈美; 長谷川 勝一; 細見 健二; 今井 憲一*; 市川 裕大; 七村 拓野; 成木 恵; 佐甲 博之; 佐藤 進; et al.

Journal of Physics; Conference Series, 1643, p.012133_1 - 012133_6, 2020/12

https://doi.org/10.1088/1742-6596/1643/1/012133
 被引用回数：2 パーセンタイル：83.94(Astronomy & Astrophysics)

We performed $$Xi$$ hypernuclear spectroscopy with the $$(K^-, K^+)$$ reaction at J-PARC to investigate the $$Xi N$$ interaction (J-PARC E05). A new experiment (J-PARC E70) in which a better energy resolution could be achieved is now being prepared. In this article, an analysis status of J-PARC E05 and a preparation status of J-PARC E70 are described.

論文

Production of $$pi^0$$ and $$eta$$ mesons in U$$+$$U collisions at $$sqrt{s_{_{NN}}}=192$$ GeV

Acharya, U.*; 長谷川 勝一; 今井 憲一*; 永宮 正治*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他397名*

Physical Review C, 102(6), p.064905_1 - 064905_13, 2020/12

https://doi.org/10.1103/PhysRevC.102.064905
 被引用回数：5 パーセンタイル：51.18(Physics, Nuclear)

The PHENIX experiment at the Relativistic Heavy Ion Collider measured $$pi^0$$ and $$eta$$ mesons at midrapidity in U$$+$$U collisions at $$sqrt{s_{_{NN}}}=192$$ GeV in a wide transverse momentum range. Measurements were performed in the $$pi^0(eta)rightarrowgammagamma$$ decay modes. A strong suppression of $$pi^0$$ and $$eta$$ meson production at high transverse momentum was observed in central U$$+$$U collisions relative to binary scaled $$p$$$$+$$$$p$$ results. Yields of $$pi^0$$ and $$eta$$ mesons measured in U$$+$$U collisions show similar suppression pattern to the ones measured in Au$$+$$Au collisions at $$sqrt{s_{_{NN}}}=200$$ GeV for similar numbers of participant nucleons. The $$eta$$/$$pi^0$$ ratios do not show dependence on centrality or transverse momentum, and are consistent with previously measured values in hadron-hadron, hadron-nucleus, nucleus-nucleus, and $$e^+e^-$$ collisions.

論文

Measurement of jet-medium interactions via direct photon-hadron correlations in Au+Au and $$d$$+Au collisions at $$sqrt{s_{_{NN}}}=200$$ GeV

Acharya, U.*; 長谷川 勝一; 今井 憲一*; 永宮 正治*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他572名*

Physical Review C, 102(5), p.054910_1 - 054910_11, 2020/11

https://doi.org/10.1103/PhysRevC.102.054910
 被引用回数：3 パーセンタイル：35.09(Physics, Nuclear)

We present direct photon-hadron correlations in 200 GeV/A Au$$+$$Au, $$d$$$$+$$Au and $$p$$$$+$$$$p$$ collisions, for direct photon $$p_T$$ from 5 - 12 GeV/$$c$$, collected by the PHENIX Collaboration in the years from 2006 to 2011. We observe no significant modification of jet fragmentation in $$d$$$$+$$Au collisions, indicating that cold nuclear matter effects are small or absent. Hadrons carrying a large fraction of the quark's momentum are suppressed in Au$$+$$Au compared to $$p$$$$+$$$$p$$ and $$d$$$$+$$Au. As the momentum fraction decreases, the yield of hadrons in Au$$+$$Au increases to an excess over the yield in $$p$$$$+$$$$p$$ collisions. The excess is at large angles and at low hadron $$p_T$$ and is most pronounced for hadrons associated with lower momentum direct photons. Comparison to theoretical calculations suggests that the hadron excess arises from medium response to energy deposited by jets.

論文

Production of $$bbar{b}$$ at forward rapidity in $$p+p$$ collisions at $$sqrt{s}=510$$ GeV

Acharya, U.*; 長谷川 勝一; 今井 憲一*; 永宮 正治*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他344名*

Physical Review D, 102(9), p.092002_1 - 092002_14, 2020/11

https://doi.org/10.1103/PhysRevD.102.092002
 被引用回数：0 パーセンタイル：0.01(Astronomy & Astrophysics)

The cross section of bottom quark-antiquark ($$bbar{b}$$) production in $$p+p$$ collisions at $$sqrt{s}=510$$ GeV is measured with the PHENIX detector at the Relativistic Heavy Ion Collider. The results are based on the yield of high mass, like-sign muon pairs measured within the PHENIX muon arm acceptance ($$1.2 < |y| < 2.2$$). The $$bbar{b}$$ signal is extracted from like-sign dimuons by utilizing the unique properties of neutral $$B$$ meson oscillation. We report a differential cross section of $$dsigma_{bbar{b} rightarrow mu^pmmu^pm}/dy = 0.16 pm 0.01~(mbox{stat}) pm 0.02~(mbox{syst}) pm 0.02~(mbox{global})$$ nb for like-sign muons in the rapidity and $$p_T$$ ranges $$1.2 < |y| < 2.2$$ and $$p_T > 1$$ GeV/$$c$$, and dimuon mass of 5 - 10 GeV/$$c^2$$. The extrapolated total cross section at this energy for $$bbar{b}$$ production is $$13.1 pm 0.6~(mbox{stat}) pm 1.5~(mbox{syst}) pm 2.7~(mbox{global})~mu$$b. The total cross section is compared to a perturbative quantum chromodynamics calculation and is consistent within uncertainties. The azimuthal opening angle between muon pairs from $$bbar{b}$$ decays and their $$p_T$$ distributions are compared to distributions generated using ${sc ps pythia 6}$, which includes next-to-leading order processes. The azimuthal correlations and pair $$p_T$$ distribution are not very well described by ${sc pythia}$ calculations, but are still consistent within uncertainties. Flavor creation and flavor excitation subprocesses are favored over gluon splitting.

論文

Measurement of displacement cross-sections of copper and iron for proton with kinetic energies in the range 0.4 - 3 GeV

松田 洋樹; 明午 伸一郎; 岩元 洋介; 吉田 誠*; 長谷川 勝一; 前川 藤夫; 岩元 大樹; 中本 建志*; 石田 卓*; 牧村 俊助*

Journal of Nuclear Science and Technology, 57(10), p.1141 - 1151, 2020/10

https://doi.org/10.1080/00223131.2020.1771453
 被引用回数：11 パーセンタイル：80.72(Nuclear Science & Technology)

加速器駆動型核変換システム(ADS)等の陽子ビーム加速器施設におけるビーム窓などの構造材の損傷評価には、原子当たりの弾き出し数(dpa)が損傷指標として広く用いられる。dpaの評価は弾き出し断面積に基づいて行われるものの、20MeV以上のエネルギー領域の陽子に対する弾き出し断面積の実験データは乏しく、計算モデルの間でも約8倍の差が存在している。このため、弾き出し断面積を実験的に取得するのは計算に用いるモデルの評価のために重要となる。弾き出し断面積の取得のため、J-PARCの加速器施設において、0.4-3GeVにわたる陽子エネルギー領域における銅と鉄の断面積を測定した。弾き出し断面積は、損傷を保持するために極低温に冷却された試料における、陽子ビームに金する抵抗率変化により得ることができる。本測定で得られた実験結果を元に、計算モデルの比較検討を行った。広く用いられているNorgertt-Robinson-Torrens (NRT)モデルは、実験値を3.5倍過大評価することが判明した。一方、近年の分子動力学に基づく非熱的再結合補正(arc)モデルは実験値をよく再現したため、銅と鉄の損傷評価にはarcモデルを使うべきであると結論づけられた。

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