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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：9 パーセンタイル：72.45(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

Identification of sub-$$mu$$s isomeric states in the odd-odd nucleus $$^{178}$$Au

Gillespie, S. A.*; Stott, A.*; Andreyev, A. N.; 他30名*

Physical Review C, 103(4), p.044307_1 - 044307_9, 2021/04

https://doi.org/10.1103/PhysRevC.103.044307
 被引用回数：1 パーセンタイル：18.91(Physics, Nuclear)

Proton-rich Au isotopes are an excellent laboratory to study shape coexistence and isomerism at low excitation energies. In this work, two new isomeric states were found in the odd-odd nuclide $$^{178}$$Au in an experiment at RITU in JYFL, Jyvaskyla. These two isomers significantly extend the current knowledge of this nucleus and pave the way to future in beam studies where they will be used to tag new gamma rays. Possible spin assignments for the new isomeric states are proposed. Finally, the new data will help clarify the poorly known $$alpha$$-decay scheme of two long-lived states in the $$^{182}$$Tl to $$^{178}$$Au decay chain.

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：45.23(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：20.63(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

Recent results from the LHCf and RHICf experiments

伊藤 好孝*; 谷田 聖; 他30名*

EPJ Web of Conferences, 208, p.05004_1 - 05004_8, 2019/05

BB2019-0930.pdf:1.22MB

https://doi.org/10.1051/epjconf/201920805004
 被引用回数：0 パーセンタイル：0.06(Astronomy & Astrophysics)

The Large Hadron Collider forward and the Relativistic Heavy Ion Collider forward experiments measured forward particles produced in high-energy hadron collisions at the LHC and RHIC. Using compact calorimeters neutral particles produced in pseudorapidities $$eta > 8.4$$ and $$eta > 6.0$$ are observed by the respective experiments. Because the collision energies ranging from 0.51 TeV to 13 TeV correspond to the cosmic-ray equivalent energies of $$10^{14}$$ to $$10^{17}$$ eV, the measurements are important to understand the hadronic interaction relevant to extensive air shower measurements. This paper reviews recent results of LHCf and initial performance of RHICf that took data in the 2017 RHIC operation.

論文

Nuclear dependence of the transverse-single-spin asymmetry for forward neutron production in polarized $$p$$$$+$$$$A$$ 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309名*

Physical Review Letters, 120, p.022001_1 - 022001_9, 2018/01

AA2017-0512.pdf:0.42MB

https://doi.org/10.1103/PhysRevLett.120.022001
 被引用回数：9 パーセンタイル：57.38(Physics, Multidisciplinary)

During 2015 the Relativistic Heavy Ion Collider (RHIC) provided collisions of transversely polarized protons with Au and Al nuclei for the first time, enabling the exploration of transverse-single-spin asymmetries with heavy nuclei. Large single-spin asymmetries in very forward neutron production have been previously observed in transversely polarized $$p+p$$ collisions at RHIC, and the existing theoretical framework that was successful in describing the single-spin asymmetry in $$p+p$$ collisions predicts only a moderate atomic-mass-number ($$A$$) dependence. In contrast, the asymmetries observed at RHIC in $$p+A$$ collisions showed a surprisingly strong $$A$$ dependence in inclusive forward neutron production. The observed asymmetry in $$p$$+Al collisions is much smaller, while the asymmetry in $$p$$ + Au collisions is a factor of three larger in absolute value and of opposite sign. The interplay of different neutron production mechanisms is discussed as a possible explanation of the observed $$A$$ dependence.

論文

Characterization of the n_TOF EAR-2 neutron beam

Chen, Y. H.*; Tassan-Got, L.*; 原田 秀郎; 木村 敦; n_TOF Collaboration*; 他130名*

EPJ Web of Conferences, 146, p.03020_1 - 03020_4, 2017/09

https://doi.org/10.1051/epjconf/201714603020
 被引用回数：1 パーセンタイル：61.21(Nuclear Science & Technology)

CERNの中性子飛行時間測定施設において、長い中性子飛行距離を有する第1実験室に加え、短い中性子飛行距離位置に第2実験室を設計・建設した。パラレル・プレート・アバランチェ・カウンター(PPAC)を用いて、第2実験室における中性子ビームの空間的広がり及びエネルギー分布を測定した。また、第1実験室で観測され時間校正に使用されてきた$$gamma$$線フラッシュは観測されないという知見が得られ、本観測結果に基づき、$$gamma$$線フラッシュの物理的起源に関する考察結果を示した。

論文

Measurement of long-range angular correlations and azimuthal anisotropies in high-multiplicity $$p$$ + 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304名*

Physical Review C, 95(3), p.034910_1 - 034910_10, 2017/03

AA2017-0048.pdf:0.55MB

https://doi.org/10.1103/PhysRevC.95.034910
 被引用回数：39 パーセンタイル：94.4(Physics, Nuclear)

We present measurements of long-range angular correlations and the transverse momentum dependence of elliptic flow $$v_2$$ in high-multiplicity $$p$$ + Au collisions at $$sqrt{s_{NN}}=200$$ GeV. A comparison of these results to previous measurements in high-multiplicity $$d$$ + Au and $$^3$$He + Au collisions demonstrates a relation between $$v_2$$ and the initial collision eccentricity $$epsilon_2$$, suggesting that the observed momentum-space azimuthal anisotropies in these small systems have a collective origin and reflect the initial geometry. Good agreement is observed between the measured $$v_2$$ and hydrodynamic calculations for all systems, and an argument disfavoring theoretical explanations based on initial momentum-space domain correlations is presented. The set of measurements presented here allows us to leverage the distinct intrinsic geometry of each of these systems to distinguish between different theoretical descriptions of the long-range correlations observed in small collision systems.

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