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佐甲 博之
Nuclear Physics A, 982, p.959 - 962, 2019/02
パーセンタイル：100(Physics, Nuclear)We aim to study extremely dense matter in heavy-ion collisions at 1-19 AGeV/c at a future project of J-PARC (JPARC-HI). We will search for the first order phase boundary and its critical end point in the QCD phase diagram. We also aim at studying the properties of dense matter related to neutron stars and neutron star mergers, in particular the equation of state (EOS). We expect to produce world's highest rate heavy-ion beams of 
with the ion species from p to U. We design spectrometers based on a large dipole magnet to measure hadrons, dimuons, and hypernuclei. We evaluate some of key performance of the spectrometers based on detailed simulations.
江川 弘行; 足利 沙希子; 長谷川 勝一; 橋本 直; 早川 修平; 細見 健二; 市川 裕大; 今井 憲一; 金原 慎二*; 七村 拓野; et al.
Progress of Theoretical and Experimental Physics (Internet), 2019(2), p.021D02_1 - 021D02_11, 2019/02
A double-
hypernucleus, 
, was observed by the J-PARC E07 collaborationin nuclear emulsions tagged by the 
reaction. This event was interpreted as a production and decay of 
,
, or 
via 
capture in 
.By assuming the capture in the atomic 3D state, the binding energy of two hyperons
(
)of these double- hypernuclei are obtained to be
, 
, and 
, respectively. Based on the kinematic fitting, is the most likely explanation for the observed event.
GeVAdare, 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
パーセンタイル：100(Physics, Nuclear)We have measured direct photons for 
GeV/
in minimum bias and 0% - 40% most central events at midrapidity for Cu
Cu collisions at GeV. The 
contribution from quasi-real direct virtual photons has been determined as an excess over the known hadronic contributions in the mass distribution. A clear enhancement of photons over the binary scaled 
fit is observed for 
GeV/ in CuCu data. The 
spectra are consistent with the AuAu data covering a similar number of participants. The inverse slopes of the exponential fits to the excess after subtraction of the baseline are 285
53(stat)57(syst)~MeV/ and 33372(stat)45(syst)~MeV/ for minimum bias and 0% - 40% most central events, respectively. The rapidity density, 
, of photons demonstrates the same power law as a function of 
observed in AuAu at the same collision energy.
and 
mesons in Cu+Au collisions at 
=200 GeVAidala, 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：1 パーセンタイル：42.26(Physics, Nuclear)Production of and mesons has been measured at midrapidity in CuAu collisions at =200 GeV. Measurements were performed in 
decay channel in the 1(2)-20 GeV/ transverse momentum range. A strong suppression is observed for and meson production at high transverse momentum in central CuAu collisions relative to the results scaled by the number of nucleon-nucleon collisions. In central collisions the suppression is similar to AuAu with comparable nuclear overlap. The 
ratio measured as a function of transverse momentum is consistent with 
-scaling parameterization down to 
2 GeV/, its asymptotic value is constant and consistent with AuAu and 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 
collisions in a range of collision energies 
3-1800 GeV. This suggests that the quark-gluon-plasma medium produced in CuCu collisions either does not affect the jet fragmentation into light mesons or it affects the and the same way.
-meson production at forward rapidity in 
collisions at 
GeV and its energy dependence from 
GeV to 7 TeVAdare, 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
パーセンタイル：100(Astronomy & Astrophysics)The PHENIX experiment at the Relativistic Heavy Ion Collider has measured the differential cross section of (1020) meson production at forward rapidity in collisions at 
510 GeV via the dimuon decay channel. The integrated cross section in the rapidity and ranges 
and 
GeV/ is 
~mb. The energy dependence of 
(
; 
GeV/) is studied using the PHENIX measurements at 200 and 510 GeV and the Large-Hadron-Collider measurements at 2.76 and 7 TeV. The experimental results are compared to various event generator predictions (pythia6, pythia8, phojet, ampt, epos3, and epos-lhc).
+Al, +Au, 
+Au, and 
He+Au at = 200 GeVAdare, A.*; 長谷川 勝一; 今井 憲一; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他362名*
Physical Review Letters, 121(22), p.222301_1 - 222301_8, 2018/11
被引用回数：2 パーセンタイル：43.36(Physics, Multidisciplinary)Asymmetric nuclear collisions of +Al, +Au, +Au, and He+Au at = 200 GeV provide an excellent laboratory for understanding particle production, as well as exploring interactions among these particles after their initial creation in the collision. We present measurements of charged hadron production in all such collision systems over a broad pseudorapidity range and as a function of collision multiplicity. A simple wounded quark model is remarkably successful at describing the full data set. We also measure the elliptic flow 
over a similarly broad pseudorapidity range. These measurements provide key constraints on models of particle emission and their translation into flow.
collisions at GeVAidala, C.*; 長谷川 勝一; 今井 憲一; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他287名*
Physical Review D, 98(7), p.072004_1 - 072004_13, 2018/10
被引用回数：1 パーセンタイル：100(Astronomy & Astrophysics)Dihadron and isolated direct photon-hadron angular correlations are measured in collisions at GeV. The correlations are sensitive to nonperturbative initial-state and final-state transverse momentum 
and 
in the azimuthal nearly back-to-back region 
. In this region, transverse-momentum-dependent evolution can be studied when several different hard scales are measured. To have sensitivity to small transverse momentum scales, nonperturbative momentum widths of 
, the out-of-plane transverse momentum component perpendicular to the trigger particle, are measured. These widths are used to investigate possible effects from transverse-momentum-dependent factorization breaking. When accounting for the longitudinal momentum fraction of the away-side hadron with respect to the near-side trigger particle, the widths are found to increase with the hard scale; this is qualitatively similar to the observed behavior in Drell-Yan and semi-inclusive deep-inelastic scattering interactions. The momentum widths are also studied as a function of center-of-mass energy by comparing to previous measurements at GeV. The nonperturbative jet widths also appear to increase with 
at a similar 
, which is qualitatively consistent to similar measurements in Drell-Yan interactions.
for forward 
production in polarized collisions at GeVAdare, 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
We have measured the cross section and single spin asymmetries from forward production in longitudinally polarized collisions at 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 
bosons provides a natural flavor separation of the participating partons.
hadrons in Au and collisions at GeVAdare, 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
パーセンタイル：100(Physics, Nuclear)We present measurements of two-particle angular correlations between high-transverse-momentum (
GeV/) observed at midrapidity (
) and particles produced either at forward (
) or backward (
) rapidity in Au and collisions at 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 
GeV/ 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 -going direction as well as in 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.
production in , Al, and Au collisions with transversely polarized proton beams at GeVAidala, C.*; 長谷川 勝一; 今井 憲一; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他286名*
Physical Review D, 98(1), p.012006_1 - 012006_11, 2018/07
被引用回数：2 パーセンタイル：37.14(Astronomy & Astrophysics)We report the transverse single-spin asymmetries of production at forward and backward rapidity, 
, as a function of transverse momentum () and Feynman-
(
). The data analyzed were recorded by the PHENIX experiment at the Relativistic Heavy Ion Collider in 2015 from , Al, and Au collisions with transversely polarized proton beams at GeV. At this collision energy, single-spin asymmetries for heavy-flavor particle production of collisions provide access to the spin-dependent gluon distribution and higher-twist correlation functions inside the nucleon, such as the gluon Qiu-Sterman and trigluon correlation functions. Proton + nucleus collisions offer an excellent opportunity to study nuclear effects on the correlation functions. The data indicate negative asymmetries at the two-standard-deviation level in the Au data for 
GeV/ at both forward and backward rapidity, while in and Al collisions the asymmetries are consistent with zero within the range of experimental uncertainties.
+ Au, + Au, and 
He
=200$ GeVAdare, A.*; 長谷川 勝一; 今井 憲一; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他347名*
Physical Review C, 97, p.064904_1 - 064904_11, 2018/06
We present measurements of the transverse-momentum dependence of elliptic flow 
for identified pions and (anti)protons at midrapidity (), in 0% - 5% central + Au and He + Au collisions at = 200 GeV. When taken together with previously published measurements in + Au collisions at = 200 GeV, the results cover a broad range of small-collision-system multiplicities and intrinsic initial geometries. We observe a clear mass-dependent splitting of 
in + Au and He + Au collisions, just as in large nucleus-nucleus (
+ ) collisions, and a smaller splitting in + Au collisions. Both hydrodynamic and transport model calculations successfully describe the data at low (
GeV/), but fail to describe various features at higher . In all systems, the values follow an approximate quark-number scaling as a function of the hadron transverse kinetic energy per constituent quark(
), which was also seen previously in + collisions.
vy-stable two-pion Bose-Einstein correlations in 
GeV AuAu collisionsAdare, 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：3 パーセンタイル：13.86(Physics, Nuclear)We present a detailed measurement of charged two-pion correlation functions in 0%-30% centrality GeV AuAu collisions by the PHENIX experiment at the Relativistic Heavy Ion Collider. The data are well described by Bose-Einstein correlation functions stemming from L
vy-stable source distributions. Using a fine transverse momentum binning, we extract the correlation strength parameter 
, the Lvy index of stability 
and the Lvy length scale parameter 
as a function of average transverse mass of the pair . 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 Lvy-stable source functions. The 
measurements indicate a decrease of the strength of the correlations at low . The Lvy length scale parameter 
decreases with increasing , following a hydrodynamically predicted type of scaling behavior. The values of the Lvy index of stability are found to be significantly lower than the Gaussian case of 
, but also significantly larger than the conjectured value that may characterize the critical point of a second-order quark-hadron phase transition.
-shell hypernucleus, 
FYang, S. B.*; 江川 弘行; 長谷川 勝一; 早川 修平; 細見 健二; 市川 裕大; 今井 憲一; 佐甲 博之; 佐藤 進; 谷田 聖; et al.
Physical Review Letters, 120, p.132505_1 - 132505_5, 2018/03
被引用回数：1 パーセンタイル：43.36(Physics, Multidisciplinary)We report on the first observation of 
rays emitted from an -shell hypernucleus, F. The energy spacing between the ground state doublet, 
and 
states, of F is determined to be 
keV by measuring the -ray energy of the 
transition. In addition, three -ray peaks are observed and assigned as 
, 
, and 
transitions. The excitation energies of the 
and 
states are determined to be 
keV and 
keV, respectively. It is found that the ground state doublet spacing is well described by theoretical models based on existing 
- and -shell hypernuclear data.
+Au Collisions at 200, 62.4, 39, and 19.6 GeV and +Au Collisions at 200 GeV and implications for collective behaviorAidala, 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：8 パーセンタイル：7.91(Physics, Multidisciplinary)Recently, multiparticle-correlation measurements of relativistic 
HeAu, 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.
佐甲 博之
JPS Conference Proceedings (Internet), 20, p.011051_1 - 011051_5, 2018/01
At J-PARC, a future project with heavy-ion collisions to study high baryon density region of the QCD phase diagram is planned. In very high energy heavy-ion collisions at RHIC and LHC, quark-gluon plasma was discovered at high temperature but very low baryon density. On the other hand, little is known about properties of high baryon density matter which can be explored with lower-energy heavy-ion collisions at J-PARC. We will discuss physics to study QCD phase structures and an experimental plan at J-PARC.
collisions at GeVAidala, 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
被引用回数：2 パーセンタイル：24.36(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 collisions at RHIC, and the existing theoretical framework that was successful in describing the single-spin asymmetry in collisions predicts only a moderate atomic-mass-number () dependence. In contrast, the asymmetries observed at RHIC in 
collisions showed a surprisingly strong dependence in inclusive forward neutron production. The observed asymmetry in +Al collisions is much smaller, while the asymmetry in + 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 dependence.
佐甲 博之
Proceedings of Science (Internet), 311, 10 Pages, 2018/01
In order to explore phase structures in high-baryon density regime of the QCD phase diagram and study dense quark/hadronic matter which may exist in the core of neutron stars, we proposed a heavy-ion program at J-PARC (J-PARC-HI). In heavy-ion collisions at J-PARC (1-19 AGeV/c), the maximum baryon density reaches 5-10 times the normal nuclear density. We designed heavy-ion acceleration scheme at J-PARC. A heavy-ion beam will be produced in a new heavy-ion injector (a linac and a booster ring) and accelerated in the existing 3-GeV and 50-GeV synchrotrons (Rapid-Cycling Synchrotron and Main Ring). We designed a multi-purpose large acceptance Toroidal magnet spectrometer for lepton, photon, and hadron measurements. We also designed a spectrometer which measures hadrons and nuclei only around beam rapidity region to search for various hypernuclei and strangelets. The latter spectrometer could accept the full beam intensity of J-PARC. In this talk, physics goals, experimental design of the spectrometers, and expected physics results will be discussed.
-meson production at forward and backward rapidity in and Cu + Au collisions at = 200 GeVAidala, C.*; 長谷川 勝一; 今井 憲一; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他456名*
Physical Review C, 96(6), p.064901_1 - 064901_18, 2017/12
被引用回数：1 パーセンタイル：100(Physics, Nuclear)The fraction of mesons which come from B-meson decay, 
, is measured for J/
rapidity 
and 
in + and Cu+Au collisions at =200 GeV with the PHENIX detector. The extracted fraction is = 0.025 0.006(stat) 0.010(syst) for + collisions. For Cu+Au collisions, is 0.094 0.028(stat) 0.037(syst) in the Au-going direction (
) and 0.089 0.026(stat) 0.040(syst) in the Cu-going direction (
). The nuclear modification factor, 
, of B mesons in Cu+Au collisions is consistent with binary scaling of measured yields in + at both forward and backward rapidity.
+ Au collisions at = 200, 62.4, 39, and 19.6 GeVAidala, C.*; 長谷川 勝一; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他246名*
Physical Review C, 96(6), p.064905_1 - 064905_21, 2017/12
被引用回数：11 パーセンタイル：6.77(Physics, Nuclear)We present measurements of the elliptic flow, , as a function of transverse momentum (), pseudorapidity (), and centrality in Au collisions at 200, 62.4, 39, and 19.6 GeV. The beam-energy scan of Au collisions provides a testing ground for the onset of flow signatures in small collision systems. We measure a nonzero signal at all four collision energies, which, at midrapidity and low , is consistent with predictions from viscous hydrodynamic models. Comparisons with calculations from parton transport models (based on the 
Monte Carlo generator) show good agreement with the data at midrapidity to forward (-going) rapidities and low . At backward (Au-going) rapidities and 
GeV/, the data diverges from calculations of relative to the initial geometry, indicating the possible dominance of nongeometry related correlations, referred to as nonflow. We also present measurements of the charged-particle multiplicity () as a function of in central Au collisions at the same energies. We find that in Au collisions at 200 GeV the scales with over all in the PHENIX acceptance. At 62.4, and 39 GeV, scales with at midrapidity and forward rapidity, but falls off at backward rapidity. This departure from the scaling may be a further indication of nonflow effects dominating at backward rapidity.
佐甲 博之; 三浦 昭彦; 宮尾 智章*; 丸田 朋史*
Proceedings of 14th Annual Meeting of Particle Accelerator Society of Japan (インターネット), p.545 - 547, 2017/12
In J-PARC Linac, from ACS to L3BT sections, highest beam loss was observed. This beam loss is considered to be caused mainly by 
generated by ionization of 
by residual gas in the beam duct. The is further changed to 
when penetrating the beam duct. We have developed a detector system consisting of 8 planes of scintillating fiber horoscopes. The upstream detector is separated from the downstream detector by about 1.2 m to measure time-of-flight of charged particles. Each detector can move in horizontal and vertical directions with stepping motors. We observed proton tracks due to beam loss for the first time at 400 MeV from April to June of 2017.
