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.
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
We have measured direct photons for GeV/ in minimum bias and 0% - 40% most central events at midrapidity for CuCu 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 28553(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.
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
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.
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
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).
Adare, 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
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.
Aidala, 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
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.
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
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.
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
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.
Aidala, 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
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.
麻生 智一; 勅使河原 誠; 長谷川 勝一; 武藤 秀生; 青柳 克弘; 野村 一隆; 高田 弘
Journal of Physics; Conference Series, 1021(1), p.012085_1 - 012085_4, 2018/06
At J-PARC's pulsed spallation neutron source, a cryogenic hydrogen system has been operated to provide liquid para-hydrogen (20K and 1.5 MPa) to the moderators since 2008. Typical operating period of the cryogenic hydrogen system was approximately 3 months continuously. However, the pressure differences between No.1, No.2 heat exchangers (HXs) and an adsorber (ADS) in the helium refrigerator had begun to increase rapidly since the beginning of 2015, the refrigerator could not be operated continuously. The impurity in the refrigerator was measured by newly introduced quadrat mass spectrometer, but no significant impurities was observed. We suspected the oil contamination from the helium compressor, as it caused performance degradation of the cryogenic system in other facilities, such as RIKEN, CERN, etc. In the summer outage in 2016, we cleaned the HXs with Freon to remove the oil contamination, and replaced the activate charcoals of ADS and oil separator (OS-5). As a result, the performance of the helium refrigerator was recovered completely.
Adare, 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.
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
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 Lvy-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.
明午 伸一郎; 松田 洋樹; 岩元 洋介; 岩元 大樹; 長谷川 勝一; 前川 藤夫; 吉田 誠*; 石田 卓*; 牧村 俊助*; 中本 建志*
Proceedings of 9th International Particle Accelerator Conference (IPAC '18) (Internet), p.499 - 501, 2018/06
Yang, 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
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.
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
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.
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
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.
Aidala, 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
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.
Aidala, 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
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.
後神 利志*; 江川 弘行; 長谷川 勝一; 早川 修平; 細見 健二; 今井 憲一; 市川 裕大; 七村 拓野; 成木 恵; 佐甲 博之; et al.
JPS Conference Proceedings (Internet), 18, p.011031_1 - 011031_6, 2017/11
The missing mass spectroscopy of hypernuclei is planned at the Japan Proton Accelerator Research Complex (J-PARC) by using the reaction. We are constructing a new magnetic spectrometer, S-2S, which has a better momentum resolution [ (FHWM)] than that of an existing spectrometer (SKS) at J-PARC. S-2S would give us an opportunity to confirm the existence of hypernuclei as a peak structure owing to both the high momentum resolution and its reasonably large solid angle. Brief descriptions of our experiment and of its preparation status are presentedin this article.
麻生 智一; 勅使河原 誠; 長谷川 勝一; 青柳 克弘*; 武藤 秀生*; 野村 一隆*; 高田 弘; 池田 裕二郎
JAEA-Technology 2017-021, 75 Pages, 2017/08