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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

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.

論文

Estimate of economic impact of atmospheric radiation storm associated with solar energetic particle events on aircraft operations

斎藤 享*; Wickramasinghe, N. K.*; 佐藤 達彦; 塩田 大幸*

Earth, Planets and Space (Internet), 73(1), p.57_1 - 57_10, 2021/12

https://doi.org/10.1186/s40623-021-01377-5
 被引用回数：3 パーセンタイル：68.24(Geosciences, Multidisciplinary)

巨大な太陽フレアが発生した際、太陽放射線による被ばく線量を低減するために航路変更を余儀なくされる場合がある。本研究では、太陽放射線被ばく警報システムWASAVIESを用いて計算した実効線量率マップに基づいて、ニューヨークから東京に飛行する航空機が、実効線量率が一定値以下になるように航路を固定して高度のみ下げた場合、及び航路及び高度の両方を調整した場合について、その増加コストを推定した。その結果、航路と高度の両方で調整した方が、全体のコスト増加は抑えられることが分かった。ただし、本推定では、線量率は時間と共に変化しないと仮定しており、将来的には、太陽放射線被ばく線量率の時間変化を考慮したより高度な航路調整アルゴリズムを開発する必要がある。

論文

Space weather benchmarks on Japanese society

石井 守*; 塩田 大幸*; 垰 千尋*; 海老原 祐輔*; 藤原 均*; 石井 貴子*; 一本 潔*; 片岡 龍峰*; 古賀 清一*; 久保 勇樹*; et al.

Earth, Planets and Space (Internet), 73(1), p.108_1 - 108_20, 2021/12

https://doi.org/10.1186/s40623-021-01420-5
 被引用回数：2 パーセンタイル：53.28(Geosciences, Multidisciplinary)

科研費新学術領域研究・太陽地球圏環境予測(PSTEP)の一環として、日本における宇宙天気災害の発生規模と頻度の関係を包括的に調査した。調査した情報は、国内における宇宙天気ユーザーが理解できる形で公開した。本論文では、その包括的調査の結果をまとめるとともに、宇宙天気災害が電力や航空業界に与える経済的損失に関して定量評価した結果も紹介する。

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307名*

Physical Review Letters, 127(16), p.162001_1 - 162001_8, 2021/10

https://doi.org/10.1103/PhysRevLett.127.162001

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

Probabilistic risk assessment of solar particle events considering the cost of countermeasures to reduce the aviation radiation dose

藤田 萌*; 佐藤 達彦; 斎藤 享*; 山敷 庸亮*

Scientific Reports (Internet), 11, p.17091_1 - 17091_9, 2021/09

https://doi.org/10.1038/s41598-021-95235-9
 被引用回数：1 パーセンタイル：26.58(Multidisciplinary Sciences)

太陽高エネルギー粒子(SEP)による航空機乗務員被ばくは、放射線防護研究において重要なトピックである。そこで、我々は、5つの太陽フレアに対して太陽放射線被ばく警報システムWASAVIESで計算した4次元線量分布マップを元に8つの航路に対する被ばく線量及び線量率を計算した。そして、過去の太陽フレア発生頻度からその被ばく線量がしきい値を超える確率を計算し、その被ばく低減対策(高度低下及びフライトキャンセル)に掛かるコストを推定した。その結果、被ばく低減対策が必要となる太陽フレアの発生頻度は、線量及び線量率で規制した場合はそれぞれ47年及び17年に1回程度で、その発生確率とコストを乗じて推定した年間被ばく低減対策リスクは1航路1年間辺り最大で約1500米ドルであった。

論文

First observation of a nuclear $$s$$-state of a $$Xi$$ hypernucleus, $$^{15}_{Xi}{rm C}$$

吉本 雅浩*; 藤田 真奈美; 橋本 直; 早川 修平; 市川 裕大; 市川 真也; 今井 憲一*; 七村 拓野; 成木 恵; 佐甲 博之; et al.

Progress of Theoretical and Experimental Physics (Internet), 2021(7), p.073D02_1 - 073D02_19, 2021/07

https://doi.org/10.1093/ptep/ptab073

Bound-systems of $$Xi^-$$-$$^{14}_{}{rm N}$$ are studied via $$Xi^-$$ capture at rest followed by emission of a twin single-$$Lambda$$ hypernucleus in the emulsion detectors. Two events forming extremely deep $$Xi^-$$ bound states were obtained by analysis of a hybrid method in the E07 experiment at J-PARC and reanalysis of the E373 experiment at KEK-PS. The decay mode of one event was assigned as $$Xi^-+^{14}_{}{rm N}to^{5}_{Lambda}{rm He}$$+$$^{5}_{Lambda}{rm He}$$+$$^{4}_{}{rm He}$$+$$n$$. Since there are no excited states for daughter particles, the binding energy of the $$Xi^-$$ hyperon, $$B_{Xi^-}$$, in $$^{14}_{}{rm N}$$ nucleus was uniquely determined to be 6.27 $$pm$$ 0.27 MeV. Another $$Xi^-$$-$$^{14}_{}{rm N}$$ system via the decay $$^{9}_{Lambda}{rm Be}$$ + $$^{5}_{Lambda}{rm He}$$ + $$n$$ brings a $$B_{Xi^-}$$ value, 8.00 $$pm$$ 0.77 MeV or 4.96 $$pm$$ 0.77 MeV, where the two possible values of $$B_{Xi^-}$$ correspond to the ground and the excited states of the daughter $$^{9}_{Lambda}{rm Be}$$ nucleus, respectively. Because the $$B_{Xi^-}$$ values are larger than those of the previously reported events (KISO and IBUKI), which are both interpreted as the nuclear $$1p$$ state of the $$Xi^-$$-$$^{14}_{}{rm N}$$ system, these new events give the first indication of the nuclear $$1s$$ state of the $$Xi$$ hypernucleus, $$^{15}_{Xi}{rm C}$$.

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：2 パーセンタイル：47.58(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：1 パーセンタイル：28.04(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：19 パーセンタイル：97.98(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

X線光電子分光における時空間計測/解析技術の開発; NAP-HARPESから4D-XPSへ

豊田 智史*; 山本 知樹*; 吉村 真史*; 住田 弘祐*; 三根生 晋*; 町田 雅武*; 吉越 章隆; 鈴木 哲*; 横山 和司*; 大橋 雄二*; et al.

Vacuum and Surface Science, 64(2), p.86 - 91, 2021/02

https://doi.org/10.1380/vss.64.86

X線光電子分光法における時空間的な測定・解析技術を開発した。はじめに、NAP-HARPES (Near Ambient Pressure Hard X-ray Angle-Resolved Photo Emission Spectroscopy)データにより、ゲート積層膜界面の時分割深さプロファイル法を開発した。この手法を用いて時分割ARPESデータからピークフィッティングとデプスプロファイリングを迅速に行う手法を確立し、4D-XPS解析を実現した。その結果、従来の最大エントロピー法(MEM)とスパースモデリングのジャックナイフ平均法を組み合わせることで、深さ方向プロファイルを高精度に実現できることがわかった。

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：0 パーセンタイル：0.09

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

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：91.42

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

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：2 パーセンタイル：40.09(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：0 パーセンタイル：0.02(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

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

https://doi.org/10.1103/PhysRevD.102.072008
 被引用回数：2 パーセンタイル：13.24(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

https://doi.org/10.1103/PhysRevD.102.032001
 被引用回数：2 パーセンタイル：25.73(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

Measurement of $$J/psi$$ at forward and backward rapidity in $$p$$+$$p$$, $$p$$$$+A$$l, $$p$$$$+A$$u, and $$^3$$He+Au collisions at $$sqrt{s_{_{NN}}}$$ = 200 GeV

Acharya, U.*; 長谷川 勝一; 今井 憲一*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他358名*

Physical Review C, 102(1), p.014902_1 - 014902_23, 2020/07

https://doi.org/10.1103/PhysRevC.102.014902
 被引用回数：6 パーセンタイル：63.81(Physics, Nuclear)

Charmonium is a valuable probe in heavy-ion collisions to study the properties of the quark gluon plasma, and is also an interesting probe in small collision systems to study cold nuclear matter effects, which are also present in large collision systems. With the recent observations of collective behavior of produced particles in small system collisions, measurements of the modification of harmonium in small systems have become increasingly relevant. We present the results of $$J/psi$$ measurements at forward and backward rapidity in various small collision systems, $$p$$$$+$$$$p$$, $$p$$$$+$$Al, $$p$$$$+$$Au and $$^3$$He$$+$$Au, at $$sqrt{s_{_{NN}}}$$=200 GeV. The results are presented in the form of the observable $$R_{AB}$$, the nuclear modification factor, a measure of the ratio of the $$J/psi$$ invariant yield compared to the scaled yield in $$p$$$$+$$$$p$$ collisions. We examine the rapidity, transverse momentum, and collision centrality dependence of nuclear effects on $$J/psi$$ production with different projectile sizes $$p$$ and $$^3$$He, and different target sizes Al and Au. The modification is found to be strongly dependent on the target size, but to be very similar for $$p$$$$+$$Au and $$^{3}$$He$$+$$Au. However, for 0% - 20% central collisions at backward rapidity, the modification for $$^{3}$$He$$+$$Au is found to be smaller than that for $$p$$$$+$$Au, with a mean fit to the ratio of $$0.89pm0.03$$(stat)$${pm}0.08$$(syst), possibly indicating final state effects due to the larger projectile size.

論文

Nuclear-modification factor of charged hadrons at forward and backward rapidity in $$p+$$Al and $$p+$$Au collisions at $$sqrt{s_{_{NN}}}=200$$ GeV

Aidala, C.*; 長谷川 勝一; 今井 憲一*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他297名*

Physical Review C, 101(3), p.034910_1 - 034910_16, 2020/03

https://doi.org/10.1103/PhysRevC.101.034910
 被引用回数：9 パーセンタイル：87.48(Physics, Nuclear)

The PHENIX experiment has studied nuclear effects in $$p$$$$+$$Al and $$p$$$$+$$Au collisions at $$sqrt{s_{_{NN}}}=200$$ GeV on charged hadron production at forward rapidity ($$1.4< eta < 2.4$$, $$p$$-going direction) and backward rapidity ($$-2.2 < eta < -1.2$$, $$A$$-going direction). Such effects are quantified by measuring nuclear modification factors as a function of transverse momentum and pseudorapidity in various collision multiplicity selections. In central $$p$$$$+$$Al and $$p$$$$+$$Au collisions, a suppression (enhancement) is observed at forward (backward) rapidity compared to the binary scaled yields in $$p$$+$$p$$ collisions. The magnitude of enhancement at backward rapidity is larger in $$p$$$$+$$Au collisions than in $$p$$$$+$$Al collisions, which have a smaller number of participating nucleons. However, the results at forward rapidity show a similar suppression within uncertainties. The results in the integrated centrality are compared with calculations using nuclear parton distribution functions, which show a reasonable agreement at the forward rapidity but fail to describe the backward rapidity enhancement.

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

https://doi.org/10.1103/PhysRevD.101.052006
 被引用回数：3 パーセンタイル：36.56(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.

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