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meson mass through 
decays佐甲 博之; 市川 真也; 成木 恵; 坂口 貴男; 佐藤 進; 他12名*
Journal of Subatomic Particles and Cosmology (Internet), 1-2, p.100012_1 - 100012_7, 2024/11
Experimental evidence for the mass and the chiral condensate of hadrons is still poor. To challenge this situation we aim to measure meson mass inside the nucleus through decays in proton-nucleus collisions at J-PARC. In this presentation we will show the experimental proposal (E88), and the status of preparation.
, 
, 
and 
mesons through their angular-dependent two-body decay modesPark, I. W.*; 佐甲 博之; 青木 和也*; Gubler, P.; Lee, S. H.*
Journal of Subatomic Particles and Cosmology (Internet), 1-2, p.100014_1 - 100014_11, 2024/11
The mass shift a spin-1 particle moving in the nuclear medium will depend on its polarization direction. To study polarization-independent mass shifts in the medium, we explore methods to isolate each polarization direction of spin-1 mesons through the angular-dependent two-body decay modes. Specifically, we study 
, 
, 
, 
and 
(
) decays. Concerning and mesons, since both particles have vacuum widths smaller than 100 MeV, they are ideal candidates for experimentally measuring chiral partners. The simultaneous observation of mass shifts of these chiral partners would provide valuable insights into the contribution of chiral symmetry breaking to the generation of hadron masses.
C
reaction at 1.8 GeV/
with the Superconducting Kaon spectrometer市川 裕大; 藤田 真奈美; 長谷川 勝一; 今井 憲一*; 七村 拓野; 成木 恵; 佐藤 進; 佐甲 博之; 田村 裕和; 谷田 聖; et al.
Progress of Theoretical and Experimental Physics (Internet), 2024(9), p.091D01_1 - 091D01_13, 2024/09
被引用回数：0 パーセンタイル：0.00(Physics, Multidisciplinary)We conducted a measurement of the inclusive missing-mass spectrum in the C
reaction at an incident beam momentum of 1.8 GeV/. This measurement was carried out utilizing the Superconducting Kaon Spectrometer (SKS) and the K1.8 beamline spectrometer at the Hadron Experimental Hall in J-PARC. Remarkably, our experimental setup yielded an exceptionaly good energy resolution of 8.2 MeV (FWHM), enabling us to observe significant enhancements in the vicinity of the 
Be threshold region. In order to estimate the spectrum information, we employed several fitting parameters assumptions. The best agreement with the spectrum shape was obtained with combining quasi-free (QF) component and two-Gaussian functions, with the experimental resolution 
being held constant. The peak positions were obtained to be 
(stat.) 
(syst.) MeV and 
(stat.) 
(syst.) MeV. Another model assumption, utilizing quasi-free (QF) and one Breit-Wigner function with 
(stat.) 
(syst.) MeV and 
(stat.) 
(syst.) MeV, also yielded a similar 
value.
and mesons through their angular-dependent decay modesPark, I. W.*; 佐甲 博之; 青木 和也*; Gubler, P.; Lee, S. H.*
Physical Review D, 109(11), p.114042_1 - 114042_10, 2024/06
被引用回数：0 パーセンタイル：0.00(Astronomy & Astrophysics)Observing the mass shifts of chiral partners will provide invaluable insight into the role of chiral symmetry breaking in the generation of hadron masses. Because both the and mesons have vacuum widths smaller than 100 MeV, they are ideal candidates for realizing mass shift measurements. On the other hand, the different momentum dependence of the longitudinal and transverse modes smear the peak positions. In this work, we analyze the angular dependence of the two-body decays of both the and . It is found that the longitudinal and transverse modes of the can be isolated by observing the pseudoscalar decay in either the forward or perpendicular directions, respectively. For the decaying into a vector meson and a pseudoscalar meson, one can accomplish the same goal by further observing the polarization of the vector meson through its angular dependence on the two pseudoscalar meson decay.
meson through dilepton and kaon decaysPark, I. W.*; 佐甲 博之; 青木 和也*; Gubler, P.; Lee, S. H.*
Physical Review D, 107(7), p.074033_1 - 074033_9, 2023/04
被引用回数：10 パーセンタイル：77.80(Astronomy & Astrophysics)Angular distributions of meson decay amplitudes of 
and 
channels are computed using both specific interaction Lagrangians and simple arguments relying on angular momentum conservation. Based on the obtained results, we assess methods to experimentally disentangle the longitudinal and transverse polarization modes of the meson and discuss advantages and disadvantages of employing either the leptonic or hadronic decay modes for this task.
Ahn, J. K.*; 長谷川 勝一; 今井 憲一*; 佐甲 博之; 佐藤 進; 谷田 聖; 他10名*
Nuclear Instruments and Methods in Physics Research A, 1047, p.167775_1 - 167775_13, 2023/02
被引用回数：1 パーセンタイル：18.16(Instruments & Instrumentation)We have constructed a conduction-cooled superconducting dipole magnet for the Hyperon spectrometer at Japan Proton Accelerator Research Complex (J-PARC). The magnet is a Helmholtz-type dipole magnet with two circular coils with a radius of 500 mm separated by 500 mm. It provides a uniform magnetic field of 1.0 T or higher in a volume of 
mm 
600 mm, covering the drift region of a time projection chamber (TPC). Owing to the target location inside the TPC, the Hyperon spectrometer has a broad angular coverage with a nearly 
solid angle. We have successfully excited the magnet up to 1.3 T. At 1.0 T, we operated it stably for more than 1 week in single-magnet configuration and double-magnet configuration with a normal-conducting 0.7-T dipole magnet located 30 cm apart. The measured magnetic field distribution in the TPC volume is consistent with the calculated field map.
atomic X-ray spectroscopy using a counter-emulsion hybrid method藤田 真奈美; 長谷川 勝一; 細見 健二; 市川 真也; 市川 裕大; Kim, S.; 七村 拓野; 佐甲 博之; 田村 裕和; 山本 剛史; et al.
Progress of Theoretical and Experimental Physics (Internet), 2022(12), p.123D01_1 - 123D01_17, 2022/12
被引用回数：1 パーセンタイル：15.88(Physics, Multidisciplinary) atomic X-ray spectroscopy is one of the most useful methods for investigation of the 
-nucleus strong interaction. Since the X-ray energy is shifted and/or broadened due to the -nucleus strong interaction compared to those calculated from electromagnetic interaction alone, the measurement of the energy shift, 
E, and the width, 
, give us information on the -nucleus potential. A serious problem in the measurement is the significant background derived from in-flight decay. A novel method of identifying stopped events using the nuclear emulsion was developed to realize the first atomic X-ray spectroscopy experiment as the J-PARC E07 experiment, which also aimed at searching for 
and hypernuclei in the emulsion. The X-rays emitted from Br and Ag atoms were measured using germanium detectors. No clear peaks were observed in the obtained spectra. However, we succeeded in reducing the background to 1/170 by this method employing coincidence measurements using nuclear emulsion and X-ray detectors.
後神 利志*; 江端 健悟; 藤田 真奈美; 原田 健志; 長谷川 勝一; 細見 健二; 市川 裕大; 今井 憲一*; Kim, S.; 七村 拓野; et al.
EPJ Web of Conferences, 271, p.11002_1 - 11002_7, 2022/11
In the K1.8 beam-line at Hadron Experimental Facility of J-PARC, a new magnetic spectrometer S-2S is being installed. S-2S was designed to achieve a high momentum resolution of 
in FWHM. Several strangeness-physics programs which require the high resolution will be realized by S-2S. The present article introduces J-PARC E70 (missing-mass spectroscopy of 
Be) and E94 (missing-mass spectroscopy of 
Li, 
B, and 
C) experiments.
三輪 浩司*; 藤田 真奈美; 原田 健志; 長谷川 勝一; 細見 健二; 市川 真也; 今井 憲一*; 佐甲 博之; 佐藤 進; 田村 裕和; et al.
EPJ Web of Conferences, 271, p.04001_1 - 04001_7, 2022/11
A new hyperon-proton scattering experiment, dubbed J-PARC E40, was performed to measure differential cross sections of the 
, 
elastic scatterings and the 
scattering by identifying a lot of 
particles in the momentum ranging from 0.4 to 0.8 GeV/ produced by the 
reactions. We successfully measured the differential cross sections of these three channels with a drastically improved accuracy with a fine angular step. These new data will become important experimental constraints to improve the theories of the two-body baryon-baryon interactions. Following this success, we proposed a new experiment to measure the differential cross sections and spin observables by using a highly polarized 
beam for providing quantitative information on the 
interaction. The results of three 
channels and future prospects of the 
scattering experiment are described.
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
被引用回数：16 パーセンタイル：83.44(Physics, Multidisciplinary)We performed a novel 
scattering experiment at the J-PARC Hadron Experimental Facility. Approximately 2400 elastic scattering events were identified from 
tagged 
particles in the momentum range 0.44 - 0.80 GeV/c. The differential cross sections of the 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 
and 
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 
. If the sign of 
is assumed to be negative, the interaction in this channel is moderately repulsive, as the Nijmegen extended-sort-core models predicted.
meson production in 
Al, Au, 
Au, and 
HeAu collisions at 
GeVAcharya, U. A.*; 長谷川 勝一; 今井 憲一*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他365名*
Physical Review C, 106(1), p.014908_1 - 014908_13, 2022/07
被引用回数：6 パーセンタイル：67.20(Physics, Nuclear)Small nuclear collisions are mainly sensitive to cold-nuclear-matter effects; however, the collective behavior observed in these collisions shows a hint of hot-nuclear-matter effects. The identified-particle spectra, especially the mesons which contain strange and antistrange quarks and have a relatively small hadronic-interaction cross section, are a good tool to study these effects. The PHENIX experiment has measured mesons in a specific set of small collision systems Al, Au, and HeAu, as well as Au, at GeV. The transverse-momentum spectra and nuclear-modification factors are presented and compared to theoretical-model predictions. The comparisons with different calculations suggest that quark-gluon plasma may be formed in these small collision systems at GeV. However, the volume and the lifetime of the produced medium may be insufficient for observing strangeness-enhancement and jet-quenching effects. Comparison with calculations suggests that the main production mechanisms of mesons at midrapidity may be different in Al versus 
HeAu collisions at GeV. While thermal quark recombination seems to dominate in HeAu collisions, fragmentation seems to be the main production mechanism in Al collisions.
nuclear modification at backward and forward rapidity in , Al, and Au collisions at GeVAcharya, U. A.*; 長谷川 勝一; 今井 憲一*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他310名*
Physical Review C, 105(6), p.064912_1 - 064912_15, 2022/06
被引用回数：15 パーセンタイル：91.22(Physics, Nuclear)Suppression of the 
nuclear-modification factor has been seen as a trademark signature of final-state effects in large collision systems for decades. In small systems, the nuclear modification was attributed to cold-nuclear-matter effects until the observation of strong differential suppression of the state in 
collisions suggested the presence of final-state effects. Results of and measurements in the dimuon decay channel are presented here for , Al, and Au collision systems at GeV. The results are predominantly shown in the form of the nuclear-modification factor, 
, the ratio of the invariant yield per nucleon-nucleon collision in collisions of proton on target nucleus to that in collisions. Measurements of the and nuclear-modification factor are compared with shadowing and transport-model predictions, as well as to complementary measurements at Large-Hadron-Collider energies.
Al, Au, Au, and 
HeAu collisions at GeV using 
productionAcharya, U. A.*; 長谷川 勝一; 今井 憲一*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他547名*
Physical Review C, 105(6), p.064902_1 - 064902_19, 2022/06
被引用回数：20 パーセンタイル：94.22(Physics, Nuclear)The PHENIX collaboration presents a systematic study of production from , Al, Au, Au, and HeAu collisions at GeV. Measurements were performed with different centrality selections as well as the total inelastic, 0% - 100%, selection for all collision systems. For 0% - 100% collisions, the nuclear modification factors, 
, are consistent with unity for 
above 8 GeV/, but exhibit an enhancement in peripheral collisions and a suppression in central collisions. The enhancement and suppression characteristics are similar for all systems for the same centrality class. It is shown that for high-- production, the nucleons in the and He interact mostly independently with the Au nucleus and that the counter intuitive centrality dependence is likely due to a physical correlation between multiplicity and the presence of a hard scattering process. These observations disfavor models where parton energy loss has a significant contribution to nuclear modifications in small systems. Nuclear modifications at lower resemble the Cronin effect - an increase followed by a peak in central or inelastic collisions and a plateau in peripheral collisions. The peak height has a characteristic ordering by system size as Au 
Au HeAu Al. For collisions with Au ions, current calculations based on initial state cold nuclear matter effects result in the opposite order, suggesting the presence of other contributions to nuclear modifications, in particular at lower .
Au, Au, and He+Au at 
= 200 GeVAcharya, U. A.*; 長谷川 勝一; 今井 憲一*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他378名*
Physical Review C, 105(2), p.024901_1 - 024901_13, 2022/02
被引用回数：12 パーセンタイル：87.03(Physics, Nuclear)There is strong evidence for the formation of small droplets of quark-gluon plasma in 
He+Au collisions at the Relativistic Heavy Ion Collider (RHIC) and in +/Pb collisions at the Large Hadron Collider. In particular, the analysis of data at RHIC for different geometries obtained by varying the projectile size and shape has proven insightful. In the present analysis, we find excellent agreement with the previously published PHENIX at RHIC results on elliptical and triangular flow with an independent analysis via the two-particle correlation method, which has quite different systematic uncertainties and an independent code base. In addition, the results are extended to other detector combinations with different kinematic (pseudorapidity) coverage. These results provide additional constraints on contributions from nonflow and longitudinal decorrelations.
, Al, and Au collisions at = 200 GeV as a function of transverse and longitudinal momentaAcharya, U. A.*; 長谷川 勝一; 今井 憲一*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他305名*
Physical Review D, 105(3), p.032004_1 - 032004_13, 2022/02
被引用回数：4 パーセンタイル：37.56(Astronomy & Astrophysics)In 2015 the PHENIX collaboration at the Relativistic Heavy Ion Collider recorded , Al, and Au collision data at center of mass energies of GeV with the proton beam(s) transversely polarized. At very forward rapidities 
relative to the polarized proton beam, neutrons were detected either inclusively or in (anti)correlation with detector activity related to hard collisions. The resulting single spin asymmetries, that were previously reported, have now been extracted as a function of the transverse momentum of the neutron as well as its longitudinal momentum fraction 
. The explicit kinematic dependence, combined with the correlation information allows for a closer look at the interplay of different mechanisms suggested to describe these asymmetries, such as hadronic interactions or electromagnetic interactions in ultra-peripheral collisions, UPC. Events that are correlated with a hard collision indeed display a mostly negative asymmetry that increases in magnitude as a function of transverse momentum with only little dependence on . In contrast, events that are not likely to have emerged from a hard collision display positive asymmetries for the nuclear collisions with a kinematic dependence that resembles that of a UPC based model. Because the UPC interaction depends strongly on the charge of the nucleus, those effects are very small for collisions, moderate for Al collisions, and large for Au collisions.
collisions at 
GeVAcharya, 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 D, 105(3), p.032003_1 - 032003_8, 2022/02
被引用回数：2 パーセンタイル：20.31(Astronomy & Astrophysics)In 2015, the PHENIX collaboration has measured single-spin asymmetries for charged pions in transversely polarized proton-proton collisions at the center of mass energy of GeV. The pions were detected at central rapidities of 
. The single-spin asymmetries are consistent with zero for each charge individually, as well as consistent with the previously published neutral-pion asymmetries in the same rapidity range. However, they show a slight indication of charge-dependent differences which may suggest a flavor dependence in the underlying mechanisms that create these asymmetries.
reaction in momentum range 470-650 MeV/三輪 浩司*; 藤田 真奈美; 長谷川 勝一; 細見 健二; 市川 裕大*; 今井 憲一*; 七村 拓野; 佐甲 博之; 佐藤 進; 田村 裕和; et al.
Physical Review Letters, 128(7), p.072501_1 - 072501_6, 2022/02
被引用回数：18 パーセンタイル：86.92(Physics, Multidisciplinary)The differential cross sections of the reaction were measured accurately for the 
momentum 
ranging from 470 to 650 MeV/ at the J-PARC Hadron Experimental Facility. Precise angular information about the reaction was obtained for the first time by detecting approximately 100 reaction events at each angular step of 
. The obtained differential cross sections show slightly forward-peaking structure in the measured momentum regions. The cross sections integrated for 
were obtained as 
mb and 
mb for 
(MeV/c) 
and 
(MeV/c)
, respectively. These results show a drastic improvement compared to past measurements of the hyperon-proton scattering experiments. They will play essential roles in updating the theoretical models of the baryon-baryon interactions.
elastic scattering in momentum range 470 to 850 MeV/三輪 浩司*; 藤田 真奈美; 長谷川 勝一; 細見 健二; 市川 裕大; 今井 憲一*; 七村 拓野; 成木 恵; 佐甲 博之; 佐藤 進; et al.
Physical Review C, 104(4), p.045204_1 - 045204_20, 2021/10
被引用回数：19 パーセンタイル：89.84(Physics, Nuclear)A high statistics scattering experiment is performed at the J-PARC Hadron Experimental Facility. Momentum-tagged 
s running in a liquid hydrogen target are accumulated by detecting the reaction with a high intensity 
beam of 20 M/spill. The differential cross sections of the elastic scattering were derived with a drastically improved accuracy by identifying approximately 4,500 events from 1.72 10
. The derived differential cross section shows a clear forward-peaking angular distribution for a momentum range from 470 to 850 MeV/. The accurate data will impose a strong constraint on the theoretical models of the baryon-baryon interactions.
collisions at 
=200 GeVAcharya, 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
被引用回数：9 パーセンタイル：61.95(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 collisions at =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.
-state of a hypernucleus, 
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
被引用回数：20 パーセンタイル：81.57(Physics, Multidisciplinary)Bound-systems of -
are studied via capture at rest followed by emission of a twin single- hypernucleus in the emulsion detectors. Two events forming extremely deep 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 
+
+
+
. Since there are no excited states for daughter particles, the binding energy of the hyperon, 
, in nucleus was uniquely determined to be 6.27 
0.27 MeV. Another - system via the decay 
+ + brings a value, 8.00 0.77 MeV or 4.96 0.77 MeV, where the two possible values of correspond to the ground and the excited states of the daughter nucleus, respectively. Because the values are larger than those of the previously reported events (KISO and IBUKI), which are both interpreted as the nuclear 
state of the - system, these new events give the first indication of the nuclear 
state of the hypernucleus, .
