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論文

Measurements of the neutron capture cross section of $$^{243}$$Am around 23.5 keV

児玉 有*; 片渕 竜也*; Rovira Leveroni, G.; 木村 敦; 中村 詔司; 遠藤 駿典; 岩本 信之; 岩本 修; 堀 順一*; 芝原 雄司*; et al.

Journal of Nuclear Science and Technology, 58(11), p.1159 - 1164, 2021/11

The neutron capture cross section of $$^{243}$$Am was measured with a pulsed neutron beam from a spallation neutron source of the Japan Proton Accelerator Research Complex. A Fe neutron beam filter was used to make the incident neutron beam mono-energetic around 23.5 keV. The neutron capture $$gamma$$-rays were detected with a NaI(Tl) detector. The pulse height weighting technique was employed to derive the neutron capture cross section from the pulse height spectrum. The cross section was determined relative to the capture cross section of $$^{197}$$Au of JENDL-4.0. The neutron capture cross section of $$^{243}$$Am was determined with a smaller uncertainty than previous measurements. The previous measurements and the JENDL-4.0 cross sections were found to be lower than the present result.

論文

Feasibility study of PGAA for boride identification in simulated melted core materials

土川 雄介; 阿部 雄太; 大石 佑治*; 甲斐 哲也; 藤 暢輔; 瀬川 麻里子; 前田 亮; 木村 敦; 中村 詔司; 原田 正英; et al.

JPS Conference Proceedings (Internet), 33, p.011074_1 - 011074_6, 2021/03

福島原子力発電所の解体作業では、溶融した燃料棒に含まれるホウ素分布を事前に把握することが重要である。溶融燃料棒の模擬試験体を用意し、ホウ素やホウ化物の含有量を調査する研究が行われてきた。本研究では、その一環として中性子を用いたホウ素並びにホウ化物分布の測定技術開発を行った。ホウ素の中性子吸収に伴う即発ガンマ線を測定し、ホウ素量や二次元分布を測定した。また、n(B,$$alpha$$$$gamma$$)反応における478keV$$gamma$$線は、ホウ素の化合状態により、$$gamma$$線ピークの幅が変化することが知られている。このことを用い、特に溶融燃料棒周辺に存在することが予測されているZrBやFeBといったホウ化物の識別可能性について調査した。測定はJ-PARC/MLFのANNRI, NOBORU, RADENにて行った。これらの解析結果について報告する。

論文

High temperature gas-cooled reactors

武田 哲明*; 稲垣 嘉之; 相原 純; 青木 健; 藤原 佑輔; 深谷 裕司; 後藤 実; Ho, H. Q.; 飯垣 和彦; 今井 良行; et al.

High Temperature Gas-Cooled Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.5, 464 Pages, 2021/02

本書は、原子力機構における今までの高温ガス炉の研究開発の総括として、HTTRの設計、燃料、炉内構造物や中間熱交換器などの要素技術の開発、出力上昇試験、950$$^{circ}$$Cの高温運転、安全性実証試験などの運転経験及び成果についてまとめたものである。また、HTTRでの知見をもとに、商用炉の設計、高性能燃料、ヘリウムガスタービン、ISプロセスによる水素製造などの要素技術開発の現状について記述しており、今後の高温ガス炉の開発に非常に有用である。本書は、日本機械学会の動力エネルギーシステム部門による化石燃料及び原子力によるエネルギーシステムの技術書のシリーズの一冊として刊行されるものである。

論文

最先端の研究開発,日本原子力研究開発機構,6; 廃止措置と廃棄物の処理処分を目指して,1; 低レベル放射性廃棄物の処理処分とウラン鉱山閉山措置に関する技術開発

辻 智之; 杉杖 典岳; 佐藤 史紀; 松島 怜達; 片岡 頌治; 岡田 翔太; 佐々木 紀樹; 井上 準也

日本原子力学会誌ATOMO$$Sigma$$, 62(11), p.658 - 663, 2020/11

日本原子力研究開発機構ではバックエンド関連の研究・技術開発として、原子力施設の廃止措置や安全で環境負荷低減につながる低レベル放射性廃棄物の処理処分技術開発と、地層処分の基盤的研究開発を進めてきた。これらバックエンドに関する原子力機構の研究・技術開発のうち、原子力施設の廃止措置や低レベル放射性廃棄物の処理処分技術開発の最前線を紹介する。

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

 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

Polarization and cross section of midrapidity $$J/psi$$ production 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(7), p.072008_1 - 072008_13, 2020/10

 被引用回数:0 パーセンタイル:0.01(Astronomy & Astrophysics)

The PHENIX experiment has measured the spin alignment for inclusive $$J/psi rightarrow e^{+}e^{-}$$ decays in $$p+p$$ collisions at $$sqrt{s}=510$$ GeV at midrapidity. The angular distributions have been measured in three different polarization frames, and the three decay angular coefficients have been extracted in a full two-dimensional analysis. Previously, PHENIX saw large longitudinal net polarization at forward rapidity at the same collision energy. This analysis at midrapidity, complementary to the previous PHENIX results, sees no sizable polarization in the measured transverse momentum range of $$0.0 < p_T < 10.0$$ GeV/$$c$$. The results are consistent with a previous one-dimensional analysis at midrapidity at $$sqrt{s}=200$$ GeV. The transverse-momentum-dependent cross section for midrapidity $$J/psi$$ production has additionally been measured, and after comparison to world data we find a simple logarithmic dependence of the cross section on $$sqrt{s}$$.

論文

Measurement of charged pion double spin asymmetries at midrapidity in longitudinally polarized $$p$$$$+$$$$p$$ 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354名*

Physical Review D, 102(3), p.032001_1 - 032001_9, 2020/08

 被引用回数:1 パーセンタイル:22.99(Astronomy & Astrophysics)

The PHENIX experiment at the Relativistic Heavy Ion Collider has measured the longitudinal double spin asymmetries, $$A_{LL}$$, for charged pions at midrapidity ($$|eta| < 0.35$$) in longitudinally polarized $$p$$$$+$$$$p$$ collisions at $$sqrt{s}=510$$ GeV. These measurements are sensitive to the gluon spin contribution to the total spin of the proton in the parton momentum fraction $$x$$ range between 0.04 and 0.09. One can infer the sign of the gluon polarization from the ordering of pion asymmetries with charge alone. The asymmetries are found to be consistent with global quantum-chromodynamics fits of deep-inelastic scattering and data at $$sqrt{s}=200$$ GeV, which show a nonzero positive contribution of gluon spin to the proton spin.

論文

VHTR technology development in Japan; Progress of R&D activities for GIF VHTR system

柴田 大受; 佐藤 博之; 植田 祥平; 竹上 弘彰; 高田 昌二; 國富 一彦

2018 GIF Symposium Proceedings (Internet), p.99 - 106, 2020/05

第四世代原子力システムの一つである超高温ガス炉(VHTR)システムについて、原子力研究開発機構で実施している研究開発活動の進捗についてまとめた。高温工学試験研究炉(HTTR)は2010年に原子炉出口温度950$$^{circ}$$Cでの50日間連続運転を達成し、その際、被覆粒子燃料の優れた品質を示した。また、高燃焼度化に向けてZrC被覆粒子の開発を進めている。炉内の構造物に用いる黒鉛の耐酸化性の向上のため、黒鉛へのSiC被覆について中性子照射の影響を調べている。将来の商用高温ガス炉コジェネレーションシステムについて、国際的な安全基準の整備を進めている。HTTRは新規制基準の適合性審査を経て、2019年に再稼働を見込んでいる。ISプロセス連続水素製造試験設備では、2016年に31時間の連続試験が完了した。HTTRでの水素製造-ガスタービン試験に向けた基本設計を完了した。

論文

$$J/psi$$ and $$psi(2S)$$ production at forward rapidity in $$p$$+$$p$$ collisions at $$sqrt{s}=510$$ GeV

Acharya, U. A.*; 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353名*

Physical Review D, 101(5), p.052006_1 - 052006_13, 2020/03

 被引用回数:2 パーセンタイル:40.85(Astronomy & Astrophysics)

The PHENIX experiment at the Relativistic Heavy Ion Collider has measured the differential cross section, mean transverse momentum, mean transverse momentum squared of inclusive $$J/psi$$ and cross-section ratio of $$psi(2S)$$ to $$J/psi$$ at forward rapidity in $$pp$$ collisions at $$sqrt{s} = 510$$ GeV via the dimuon decay channel. Comparison is made to inclusive $$J/psi$$ cross sections measured at $$sqrt{s} = 200$$ GeV and 2.76 - 13 TeV. The result is also compared to leading-order nonrelativistic QCD calculations coupled to a color-glass-condensate description of the low-$$x$$ gluons in the proton at low transverse momentum ($$p_T$$) and to next-to-leading order nonrelativistic QCD calculations for the rest of the $$p_T$$ range. These calculations overestimate the data at low $$p_T$$. While consistent with the data within uncertainties above $$approx 3$$ GeV/$$c$$, the calculations are systematically below the data. The total cross section times the branching ratio is BR $$dsigma^{J/psi}_{pp}/dy (1.2 < |y| < 2.2, 0 < p_T < 10$$ GeV/$$c$$) = 54.3 $$pm$$ 0.5 (stat) $$pm$$ 5.5 (syst) nb.

論文

The Deposition densities of radiocesium and the air dose rates in undisturbed fields around the Fukushima Dai-ichi Nuclear Power Plant; Their temporal changes for five years after the accident

三上 智; 田中 博幸*; 松田 秀夫*; 佐藤 昭二*; 星出 好史*; 奥田 直敏*; 鈴木 健夫*; 坂本 隆一*; 安藤 正樹; 斎藤 公明

Journal of Environmental Radioactivity, 210, p.105941_1 - 105941_12, 2019/12

AA2019-0019.pdf:2.65MB

 被引用回数:17 パーセンタイル:84.46(Environmental Sciences)

2011年から2016年にかけて福島第一原子力発電所から80km圏内の撹乱のない多数の測定点で放射性セシウムの沈着量と空間線量率を繰り返し測定し、それらの経時変化の特徴を明らかにした。この地域のバックグラウンド放射線量を除いた平均空間線量率は、2011年6月から2016年8月までの期間中に初期の約20%に減少した。これは主に$$^{134}$$Cs(半減期2.06y)の壊変の結果である。空間線量率の減少は放射性セシウムの壊変から予想されるものよりも約2倍早く、この減少の大部分は放射性セシウムの土壌への浸透によるものである。除染されていない土壌における$$^{134}$$Csと$$^{137}$$Csの平均沈着量は、ほぼ放射性壊変から予想されるペースで減少していた。すなわち水平方向の放射性セシウムの移動が比較的小さいことを示した。空間線量率と沈着量の測定結果では除染の効果が明らかに観察された。測定点の平均空間線量率は、その詳細な定量分析は今後の課題だが、除染やその他の人間の活動によって約20%減少した。

論文

Beam energy and centrality dependence of direct-photon emission from ultrarelativistic heavy-ion collisions

Adare, A.*; 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666名*

Physical Review Letters, 123(2), p.022301_1 - 022301_10, 2019/07

 被引用回数:13 パーセンタイル:83.95(Physics, Multidisciplinary)

The PHENIX collaboration presents first measurements of low-momentum (0.4 $$< p_T <$$ 3 GeV/$$c$$) direct-photon yields from Au$$+$$Au collisions at $$sqrt{s_{_{NN}}}$$ = 39 and 62.4 GeV. For both beam energies the direct-photon yields are substantially enhanced with respect to expectations from prompt processes, similar to the yields observed in Au$$+$$Au collisions at $$sqrt{s_{_{NN}}}$$ = 200. Analyzing the photon yield as a function of the experimental observable $$dN_{rm ch}/deta$$ reveals that the low-momentum ($$>$$1 GeV/$$c$$) direct-photon yield $$dN_{gamma}^{rm dir}/deta$$ is a smooth function of $$dN_{rm ch}/deta$$ and can be well described as proportional to $$(dN_{rm ch}/deta)^alpha$$ with $$alpha approx$$ 1.25. This new scaling behavior holds for a wide range of beam energies at the Relativistic Heavy Ion Collider and Large Hadron Collider, for centrality selected samples, as well as for different, $$A+A$$ collision systems. At a given beam energy the scaling also holds for high $$p_T$$ ($$>$$5 GeV/$$c$$) but when results from different collision energies are compared, an additional $$sqrt{s_{_{NN}}}$$-dependent multiplicative factor is needed to describe the integrated-direct-photon yield.

論文

Measurement of two-particle correlations with respect to second- and third-order event planes in Au$$+$$Au collisions at $$sqrt{s_{_{NN}}}=200$$ GeV

Adare, A.*; 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451名*

Physical Review C, 99(5), p.054903_1 - 054903_29, 2019/05

AA2019-0567.pdf:3.42MB

 被引用回数:8 パーセンタイル:84.14(Physics, Nuclear)

We present measurements of azimuthal correlations of charged hadron pairs in $$sqrt{s_{_{NN}}}=200$$ GeV Au$$+$$Au collisions after subtracting an underlying event using a model that includes higher-order azimuthal anisotropy $$v_2$$, $$v_3$$, and $$v_4$$. After subtraction, the away-side ($$Deltaphisimpi)$$ of the highest transverse-momentum trigger ($$p_T > 4$$ GeV/$$c$$) correlations is suppressed compared to that of correlations measured in $$p$$$$+$$$$p$$ collisions. At the lowest associated particle $$p_T$$, the away-side shape and yield are modified. These observations are consistent with the scenario of radiative-jet energy loss. For the lowest-$$p_T$$ trigger correlations, an away-side yield exists and we explore the dependence of the shape of the away-side within the context of an underlying-event model. Correlations are also studied differentially versus event-plane angle $$Psi_n$$. The angular correlations show an asymmetry when selecting the sign of the trigger-particle azimuthal angle with respect to the $$Psi_2$$ event plane. This asymmetry and the measured suppression of the pair yield out of plane is consistent with a path-length-dependent energy loss. No $$Psi_3$$ dependence can be resolved within experimental uncertainties.

論文

Low-momentum direct-photon measurement in Cu + Cu collisions at $$sqrt{s_{_{NN}}}=200$$ GeV

Adare, A.*; 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448名*

Physical Review C, 98(5), p.054902_1 - 054902_11, 2018/11

 被引用回数:10 パーセンタイル:76.63(Physics, Nuclear)

We have measured direct photons for $$p_T< 5~$$GeV/$$c$$ in minimum bias and 0% - 40% most central events at midrapidity for Cu$$+$$Cu collisions at $$sqrt{s_{_{NN}}}=200$$ GeV. The $$e^{+}e^{-}$$ contribution from quasi-real direct virtual photons has been determined as an excess over the known hadronic contributions in the $$e^{+}e^{-}$$ mass distribution. A clear enhancement of photons over the binary scaled $$p$$$$+$$$$p$$ fit is observed for $$p_T < 4$$ GeV/$$c$$ in Cu$$+$$Cu data. The $$p_T$$ spectra are consistent with the Au$$+$$Au data covering a similar number of participants. The inverse slopes of the exponential fits to the excess after subtraction of the $$p$$$$+$$$$p$$ baseline are 285$$pm$$53(stat)$$pm$$57(syst)~MeV/$$c$$ and 333$$pm$$72(stat)$$pm$$45(syst)~MeV/$$c$$ for minimum bias and 0% - 40% most central events, respectively. The rapidity density, $$dN/dy$$, of photons demonstrates the same power law as a function of $$dN_{rm ch}/deta$$ observed in Au$$+$$Au at the same collision energy.

論文

Production of $$pi^0$$ and $$eta$$ mesons in Cu+Au collisions at $$sqrt{s_{_{NN}}}$$=200 GeV

Aidala, C.*; 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, 98(5), p.054903_1 - 054903_11, 2018/11

 被引用回数:5 パーセンタイル:56.63(Physics, Nuclear)

Production of $$pi^0$$ and $$eta$$ mesons has been measured at midrapidity in Cu$$+$$Au collisions at $$sqrt{s_{_{NN}}}$$=200 GeV. Measurements were performed in $$pi^0(eta)rightarrowgammagamma$$ decay channel in the 1(2)-20 GeV/$$c$$ transverse momentum range. A strong suppression is observed for $$pi^0$$ and $$eta$$ meson production at high transverse momentum in central Cu$$+$$Au collisions relative to the $$p$$$$+$$$$p$$ results scaled by the number of nucleon-nucleon collisions. In central collisions the suppression is similar to Au$$+$$Au with comparable nuclear overlap. The $$eta/pi^0$$ ratio measured as a function of transverse momentum is consistent with $$m_T$$-scaling parameterization down to $$p_T=$$2 GeV/$$c$$, its asymptotic value is constant and consistent with Au$$+$$Au and $$p$$$$+$$$$p$$ and does not show any significant dependence on collision centrality. Similar results were obtained in hadron-hadron, hadron-nucleus, and nucleus-nucleus collisions as well as in $$e^+e^-$$ collisions in a range of collision energies $$sqrt{s_{_{NN}}}=$$ 3-1800 GeV. This suggests that the quark-gluon-plasma medium produced in Cu$$+$$Cu collisions either does not affect the jet fragmentation into light mesons or it affects the $$pi^0$$ and $$eta$$ the same way.

論文

Measurement of $$phi$$-meson production at forward rapidity in $$p+p$$ collisions at $$sqrt{s}=510$$ GeV and its energy dependence from $$sqrt{s}=200$$ GeV to 7 TeV

Adare, A.*; 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351名*

Physical Review D, 98(9), p.092006_1 - 092006_13, 2018/11

 被引用回数:0 パーセンタイル:0.01(Astronomy & Astrophysics)

The PHENIX experiment at the Relativistic Heavy Ion Collider has measured the differential cross section of $$phi$$(1020) meson production at forward rapidity in $$p$$$$+$$$$p$$ collisions at $$sqrt{s}=$$510 GeV via the dimuon decay channel. The integrated cross section in the rapidity and $$p_T$$ ranges $$1.2 < |y| < 2.2$$ and $$2 < p_T < 7$$ GeV/$$c$$ is $$sigma_phi=2.79 pm 0.20,{rm (stat)} pm 0.17,{rm (syst)} pm 0.34, {rm (norm)} times 10^{-2}$$~mb. The energy dependence of $$sigma_phi$$ ($$1.2 < |y|<2.2$$; $$2<p_T<5$$ GeV/$$c$$) is studied using the PHENIX measurements at $$sqrt{s}=$$200 and 510 GeV and the Large-Hadron-Collider measurements at $$sqrt{s}=$$2.76 and 7 TeV. The experimental results are compared to various event generator predictions (pythia6, pythia8, phojet, ampt, epos3, and epos-lhc).

論文

Numerical evaluation on fluctuation absorption characteristics based on nuclear heat supply fluctuation test using HTTR

高田 昌二; 本多 由貴*; 稲葉 良知; 関田 健司; 根本 隆弘; 栃尾 大輔; 石井 俊晃; 佐藤 博之; 中川 繁昭; 沢 和弘*

Proceedings of 9th International Topical Meeting on High Temperature Reactor Technology (HTR 2018) (USB Flash Drive), 7 Pages, 2018/10

HTGRに接続する核熱利用システムの設計では、化学プラント会社の容易な参入を可能にするため、非原子炉級で設計されるが、熱利用システムで異常が発生した場合でも原子炉の運転を継続できることとしている。需要地近接立地で負荷追従運転を実現するため、原子炉入口および出口冷却材温度を一定に保ちながら一次系ガス圧力を変化させるインベントリ制御は原子炉出力を制御する方法の候補の1つとされている。HTTRを用いた非核加熱運転による熱負荷変動吸収試験結果をもとに、異なる一次系ガス圧力で原子炉入口温度をステップ状に変動させた。数値解析の結果、圧力の低下により変動吸収特性が劣化しないことが明らかになった。また、原子炉出力の80%でも、原子炉出口温度がスクラムレベルに達しないことも明らかにした。

論文

Cross section and longitudinal single-spin asymmetry $$A_L$$ for forward $$W^{pm}rightarrowmu^{pm}nu$$ production in polarized $$p$$$$+$$$$p$$ collisions at $$sqrt{s}=510$$ GeV

Adare, A.*; 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423名*

Physical Review D, 98(3), p.032007_1 - 032007_14, 2018/08

 被引用回数:10 パーセンタイル:63.01(Astronomy & Astrophysics)

We have measured the cross section and single spin asymmetries from forward $$W^{pm}rightarrowmu^{pm}nu$$ production in longitudinally polarized $$p$$$$+$$$$p$$ collisions at $$sqrt{s}=510$$ GeV using the PHENIX detector at the Relativistic Heavy Ion Collider. The cross sections are consistent with previous measurements at this collision energy, while the most forward and backward longitudinal single spin asymmetries provide new insights into the sea quark helicities in the proton. The charge of the $$W$$ bosons provides a natural flavor separation of the participating partons.

論文

Measurement of emission angle anisotropy via long-range angular correlations with high-$$p_T$$ hadrons in $$d$$$$+$$Au and $$p$$$$+$$$$p$$ collisions at $$sqrt{s_{_{NN}}}=200$$ GeV

Adare, A.*; 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468名*

Physical Review C, 98(1), p.014912_1 - 014912_16, 2018/07

 被引用回数:5 パーセンタイル:49.58(Physics, Nuclear)

We present measurements of two-particle angular correlations between high-transverse-momentum ($$2<p_T<11$$ GeV/$$c$$) $$pi^0$$ observed at midrapidity ($$|eta|<0.35$$) and particles produced either at forward ($$3.1<eta<3.9$$) or backward ($$-3.7<eta<-3.1$$) rapidity in $$d$$$$+$$Au and $$p$$$$+$$$$p$$ collisions at $$sqrt{s_{_{NN}}}=200$$ GeV. The azimuthal angle correlations for particle pairs with this large rapidity gap in the Au-going direction exhibit a ridge-like structure that persists up to $$p_T{approx}6$$ GeV/$$c$$ and which strongly depends on collision centrality, which is a similar characteristic to the hydrodynamical particle flow in A+A collisions. The ridge-like structure is absent in the $$d$$-going direction as well as in $$p$$$$+$$$$p$$ collisions, in the transverse-momentum range studied. The results indicate that the ridge-like structure is shifted in the Au-going direction toward more central collisions, similar to the charged-particle pseudorapidity distributions.

論文

L$'{e}$vy-stable two-pion Bose-Einstein correlations in $$sqrt{s_{NN}}=200$$ GeV Au$$+$$Au collisions

Adare, A.*; 長谷川 勝一; 永宮 正治; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他448名*

Physical Review C, 97(6), p.064911_1 - 064911_22, 2018/06

 被引用回数:21 パーセンタイル:92.92(Physics, Nuclear)

We present a detailed measurement of charged two-pion correlation functions in 0%-30% centrality $$sqrt{s_{_{NN}}}=200$$ GeV Au$$+$$Au collisions by the PHENIX experiment at the Relativistic Heavy Ion Collider. The data are well described by Bose-Einstein correlation functions stemming from L$'e$vy-stable source distributions. Using a fine transverse momentum binning, we extract the correlation strength parameter $$lambda$$, the L$'e$vy index of stability $$alpha$$ and the L$'e$vy length scale parameter $$R$$ as a function of average transverse mass of the pair $$m_T$$. We find that the positively and the negatively charged pion pairs yield consistent results, and their correlation functions are represented, within uncertainties, by the same L$'e$vy-stable source functions. The $$lambda(m_T)$$ measurements indicate a decrease of the strength of the correlations at low $$m_T$$. The L$'e$vy length scale parameter $$R(m_T)$$ decreases with increasing $$m_T$$, following a hydrodynamically predicted type of scaling behavior. The values of the L$'e$vy index of stability $$alpha$$ are found to be significantly lower than the Gaussian case of $$alpha=2$$, but also significantly larger than the conjectured value that may characterize the critical point of a second-order quark-hadron phase transition.

論文

Measurements of $$e^+e^-$$ pairs from open heavy flavor in $$p+p$$ and $$d+A$$ collisions at $$sqrt{s_{NN}}$$ = 200 GeV

Adare, A.*; 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497名*

Physical Review C, 96(2), p.024907_1 - 024907_19, 2017/08

AA2017-0466.pdf:2.14MB

 被引用回数:11 パーセンタイル:76.57(Physics, Nuclear)

We report a measurement of $$e^+e^-$$ pairs from semileptonic heavy-flavor decays in $$p+p$$ collisions at $$sqrt{s_{NN}}$$ = 200 GeV. The $$e^+e^-$$ pair yield from $$bbar{b}$$ and $$cbar{c}$$ is separated by exploiting a double differential fit done simultaneously in dielectron invariant mass and $$p_T$$. We used three different event generators, ${sc pythia}$, ${sc mc@nlo}$, and ${sc powheg}$, to simulate the $$e^+e^-$$ spectra from $$bbar{b}$$ and $$cbar{c}$$ production. The data can be well described by all three generators within the detector acceptance. However, when using the generators to extrapolate to $$4pi$$, significant differences are observed for the total cross section. These difference are less pronounced for $$bbar{b}$$ than for $$cbar{c}$$. The same model dependence was observed in already published $$d+A$$ data. The $$p+p$$ data are also directly compared with $$d+A$$ data in mass and $$p_T$$, and within the statistical accuracy no nuclear modification is seen.

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