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Walter, H.*; Colonna, M.*; Cozma, D.*; Danielewicz, P.*; Ko, C. M.*; Kumar, R.*; 小野 章*; Tsang, M. Y. B*; Xu, J.*; Zhang, Y.-X.*; et al.
Progress in Particle and Nuclear Physics, 125, p.103962_1 - 103962_90, 2022/07
被引用回数:32 パーセンタイル:96.94(Physics, Nuclear)原子核-原子核衝突や原子核の状態方程式の研究において、反応計算モデルは重要なツールとなり、世界中で開発が進んでいる。本論文は、原子力機構のJQMD-2.0を含め、現在開発中の複数のコード開発者の協力により、これらコードを同じ条件で比較することで共通点や差異を明らかにしたプロジェクトTransport Model Evaluation Project (TMEP)を総括したものである。参加したコードはBoltzmann-Uehling-Uhlenbeck(BUU)法に基づく13のコードと、Quantum Molecular Dynamics (QMD)法に基づく12のコードであった。プロジェクトでは、Au原子核同士を衝突させてその終状態を観測する現実的な計算や、一辺が640nmの箱に核子を詰めて時間発展させる仮想的な計算を行った。その結果、BUU法コードとQMD法コードは計算原理が異なるため、計算の設定に関係なく系統的な差異が生じることが明らかになった。その一方で、同じ方法を採用するコード間の比較では、時間発展を細かく計算することでコード間の差は埋まっていき、一定の収束値を持つことが示された。この結果は今後開発される同分野のコードのベンチマークデータとして有用なものであるだけでなく、原子核基礎物理学の実験や理論研究の標準的な指針としても役に立つことが期待される。
Li, H.*; 谷田 聖; Belle Collaboration*; 他131名*
Physical Review D, 100(9), p.092008_1 - 092008_26, 2019/11
被引用回数:8 パーセンタイル:48.75(Astronomy & Astrophysics)This work reports the first observation of azimuthal asymmetries around the thrust axis in annihilation of pairs of back-to-back charged pions in one hemisphere, and
and
mesons in the opposite hemisphere. These results are complemented by a new analysis of pairs of back-to-back charged pions. The
and
asymmetries rise with the relative momentum
of the detected hadrons as well as with the transverse momentum with respect to the thrust axis. These asymmetries are sensitive to the Collins fragmentation function
and provide complementary information to previous measurements with charged pions and kaons in the final state. In particular, the
final states will provide additional information on the flavor structure of
. This is the first measurement of the explicit transverse-momentum dependence of the Collins fragmentation function from Belle data. It uses a dataset of 980.4 fb
collected by the Belle experiment at or near a center-of-mass energy of 10.58 GeV.
Flavigny, F.*; Elseviers, J.*; Andreyev, A. N.; Bauer, C.*; Bildstein, V.*; Blazhev, A.*; 他31名*
Physical Review C, 99(5), p.054332_1 - 054332_6, 2019/05
被引用回数:7 パーセンタイル:63.98(Physics, Nuclear)The Ni isotope is known for exhibiting signs of shape coexistence at very low excitation energies. In this work, carried out at REX-Isolde, CERN, the
Ni(
,
) reaction in inverse kinematics was studied for the first time and used to assess directly the active neutrons orbitals responsible its shape coexistence. The main states populated were the
ground state, the second
state at 1604~keV, and the first excited 2
state at 2033 keV. The analysis of the differential transfer cross-sections and comparison with theoretical DWBA calculations permitted to quantify the contribution of neutron orbits below the
=40 gap in the structure of these states. This information is essential to better understand the phenomenon of shape coexistence in the region of medium-heavy nuclei.
Aidala, C.*; 長谷川 勝一; 今井 憲一; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他312名*
Nature Physics, 15(3), p.214 - 220, 2019/03
被引用回数:142 パーセンタイル:99.18(Physics, Multidisciplinary)Experimental studies of the collisions of heavy nuclei at relativistic energies have established the properties of the quark-gluon plasma (QGP), a state of hot, dense nuclear matter in which quarks and gluons are not bound into hadrons. In this state, matter behaves as a nearly inviscid fluid that efficiently translates initial spatial anisotropies into correlated momentum anisotropies among the particles produced, creating a common velocity field pattern known as collective flow. In recent years, comparable momentum anisotropies have been measured in small-system proton-proton and proton-nucleus (p+A) collisions, despite expectations that the volume and lifetime of the medium produced would be too small to form a QGP. Here we report on the observation of elliptic and triangular flow patterns of charged particles produced in proton-gold (p+Au), deuteron-gold (d+Au) and helium-gold (He+Au) collisions at a nucleon-nucleon centre-of-mass energy
= 200 GeV. The unique combination of three distinct initial geometries and two flow patterns provides unprecedented model discrimination. Hydrodynamical models, which include the formation of a short-lived QGP droplet, provide the best simultaneous description of these measurements.
Adare, A.*; 長谷川 勝一; 今井 憲一; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他317名*
Physical Review C, 99(2), p.024903_1 - 024903_16, 2019/02
被引用回数:11 パーセンタイル:75.38(Physics, Nuclear)We present measurements of elliptic and triangular azimuthal anisotropy of charged particles detected at forward rapidity in Au
Au collisions at
GeV, as a function of centrality. The multiparticle cumulant technique is used to obtain the elliptic flow coefficients
,
,
, and
, and triangular flow coefficients
and
. Using the small-variance limit, we estimate the mean and variance of the event-by-event
distribution from
and
. In a complementary analysis, we also use a folding procedure to study the distributions of
and
directly, extracting both the mean and variance. Implications for initial geometrical fluctuations and their translation into the final state momentum distributions are discussed.
Aidala, C.*; 長谷川 勝一; 今井 憲一; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他311名*
Physical Review Letters, 120(6), p.062302_1 - 062302_8, 2018/02
被引用回数:41 パーセンタイル:90.66(Physics, Multidisciplinary)Recently, multiparticle-correlation measurements of relativistic He
Au,
Pb, and even
collisions have shown surprising collective signatures. Here we present beam-energy-scan measurements of 2-, 4-, and 6-particle angular correlations in
Au collisions at
=200, 62.4, 39, and 19.6 GeV. We also present measurements of 2- and 4-particle angular correlations in
Au collisions at
=200 GeV. We find the 4-particle cumulant to be real-valued for
Au collisions at all four energies. We also find that the 4-particle cumulant in
Au has the opposite sign as that in
Au, indicating that the correlations are geometrical and therefore collective in origin. Further we find that the 6-particle cumulant agrees with the 4-particle cumulant in
Au collisions at 200 GeV, which indicates that nonflow effects are subdominant and provides strong evidence of collectivity.
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431名*
Physical Review D, 95(11), p.112001_1 - 112001_15, 2017/06
被引用回数:16 パーセンタイル:63.84(Astronomy & Astrophysics)The cross section and transverse single-spin asymmetries of and
from open heavy-flavor decays in polarized
collisions at
= 200 GeV were measured by the PHENIX experiment during 2012 at the Relativistic Heavy Ion Collider. Because heavy-flavor production is dominated by gluon-gluon interactions at
= 200 GeV, these measurements offer a unique opportunity to obtain information on the trigluon correlation functions. The measurements are performed at forward and backward rapidity (
) over the transverse momentum range of
GeV/
for the cross section and
GeV/
for the asymmetry measurements. The obtained cross section is compared to a fixed-order-plus-next-to-leading-log perturbative-quantum-chromodynamics calculation. The asymmetry results are consistent with zero within uncertainties, and a model calculation based on twist-3 three-gluon correlations agrees with the data.
永江 知文*; 江川 弘行; 長谷川 勝一; 細見 健二; 市川 裕大; 今井 憲一; 佐甲 博之; 佐藤 進; 杉村 仁志; 谷田 聖; et al.
Proceedings of Science (Internet), 281, p.038_1 - 038_7, 2017/05
We have carried out a pilot data taking of the J-PARC E05 experiment to search for the bound state peaks of Be in the
C
reaction at 1.8 GeV/
. The measurement was performed at the K1.8 beam line of the J-PARC hadron experimental hall with a typical
beam intensity of
every six seconds. So far the best energy resolution of about 6 MeV FWHM was achieved with the existing SKS spectrometer. With a reasonable statistics, we have succeeded to observe peak structures in the bound region, which seems to suggest that the potential depth of
would be deeper than 14 MeV estimated in the previous measurements.
市川 裕大; 江川 弘行; 長谷川 勝一; 早川 修平; 細見 健二; 今井 憲一; 金原 慎二; 中田 祥之; 佐甲 博之; 佐藤 進; et al.
JPS Conference Proceedings (Internet), 13, p.020007_1 - 020007_5, 2017/02
これまで反K中間子と原子核の間の相互作用はK中間子原子(K-中間子と原子核の電磁相互作用による束縛状態)のX線を用いて研究が行われてきた。しかし、このK中間子原子のX線測定では理論モデルの種類によって結果が大きく依存するという問題がため、X線測定だけでは相互作用を決定することが困難である。そこで、われわれはC(K
, p)反応におけるエネルギースペクトルを測定し、理論計算と比較する手法を用いて反K中間子と原子核の間の相互作用を決定しようとしている。この手法は既にKEK E548実験で行われているが、実験セットアップ上の問題点が指摘されているため、過去の高エネルギー加速器研究機構での実験では不十分である。そこで、われわれはJ-PARCにおいて再実験を行い、正しく
C(K
, p)のスペクトルを取得することに成功した。
山我 拓巳*; 谷田 聖; J-PARC E31 Collaboration*; 他70名*
JPS Conference Proceedings (Internet), 8, p.021016_1 - 021016_5, 2015/09
We are planning to carry out an experimental study of hyperon resonance via the reaction using kaon beam which has momentum of 1 GeV/
at the J-PARC hadron experimental facility. In the presented reaction,
can be produced dynamically from meson-baryon resonant state. The performance of the counters was tested at the previous beam time of the J-PARC. The counters worked as expected. The preparation of experimental setup had been done.
高橋 智則*; 江川 弘行; 早川 修平; 細見 健二; 市川 裕大; 今井 憲一; 佐甲 博之; 佐藤 進; 杉村 仁志; 谷田 聖; et al.
JPS Conference Proceedings (Internet), 8, p.022011_1 - 022011_6, 2015/09
A search for the pentaquark in the
reaction was performed at the J-PARC Hadron Facility. Two data samples were collected in 2010 and 2012 at
beam momenta of 1.92 and 2.0 GeV/
, respectively. No peak structure was observed in the missing mass spectra obtained from either data set. The upper limit for the production cross section averaged over the scattering-angle range of
to
in the laboratory frame was found to be 0.28
b/sr. The decay width of the
can be directly connected to the production cross section through a theoretical calculation using an effective Lagrangian. The estimated upper limits of the width were 0.41 and 2.8 MeV for the spin-parities of
and
, respectively.