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Journal Articles

How different is the core of $$^{25}$$F from $$^{24}$$O$$_{g.s.}$$ ?

Tang, T. L.*; Uesaka, Tomohiro*; Kawase, Shoichiro; Beaumel, D.*; Dozono, Masanori*; Fujii, Toshihiko*; Fukuda, Naoki*; Fukunaga, Taku*; Galindo-Uribarri. A.*; Hwang, S. H.*; et al.

Physical Review Letters, 124(21), p.212502_1 - 212502_6, 2020/05

 Times Cited Count:1 Percentile:30.13(Physics, Multidisciplinary)

The structure of a neutron-rich $$^{25}$$F nucleus is investigated by a quasifree ($$p,2p$$) knockout reaction. The sum of spectroscopic factors of $$pi 0d_{5/2}$$ orbital is found to be 1.0 $$pm$$ 0.3. The result shows that the $$^{24}$$O core of $$^{25}$$F nucleus significantly differs from a free $$^{24}$$O nucleus, and the core consists of $$sim$$35% $$^{24}$$O$$_{rm g.s.}$$, and $$sim$$65% excited $$^{24}$$O. The result shows that the $$^{24}$$O core of $$^{25}$$F nucleus significantly differs from a free $$^{24}$$O nucleus. The result may infer that the addition of the $$0d_{5/2}$$ proton considerably changes the neutron structure in $$^{25}$$F from that in $$^{24}$$O, which could be a possible mechanism responsible for the oxygen dripline anomaly.

Journal Articles

Baryon spectroscopy in $$(pi,2pi)$$ reactions with 10$$^{6}$$Hz pion beams at J-PARC

Sako, Hiroyuki; Hasegawa, Shoichi; Hosomi, Kenji; Ichikawa, Yudai; Imai, Kenichi; Hicks, K.*; Ahn, J. K.*; Kim, S. H.*; Lee, J. W.*; Hwang, S. H.*

Proceedings of Science (Internet), 5 Pages, 2017/05

Although baryon resonances have been studied for a long time, our knowledge on their properties are still limited. Recently a Dynamical-Couple Channel (DCC) model shows there are significant contributions of $$(pi,2pi)$$ reactions to these baryon resonances. However, there are only 240 thousand events of $$(pi, 2pi)$$ reaction data measured in 1970's. Thus, we proposed an experiment E45 to study baryon resonances in $$(pi,2pi)$$ reaction utilizing $$10^6$$ Hz $$pi$$ beams at J-PARC. We aim at clarifying most of baryon mass levels. We measure these reactions in a large acceptance Time Projection Chamber inside a Helmholtz dipole magnet. We will measure these reactions in small momentum steps over a large beam momentum range and perform partial wave analysis to extract properties of each resonance. In this presentation, we will show the experimental design, expected results in simulations, and the status of the detectors.

Journal Articles

Cosmic-ray test of a time-of-flight detector for double-strangeness experiments at J-PARC

Kim, S. H.*; Hwang, S.; Ahn, J. K.*; Ekawa, Hiroyuki; Hayakawa, Shuhei; Hong, B.*; Hosomi, Kenji; Imai, Kenichi; Kim, M. H.*; Lee, J. Y.*; et al.

Nuclear Instruments and Methods in Physics Research A, 795, p.39 - 44, 2015/09

 Times Cited Count:3 Percentile:63.46(Instruments & Instrumentation)

Journal Articles

Development of a prototype GEM TPC with a gating grid for an H-dibaryon search experiment at J-PARC

Sako, Hiroyuki; Sugimura, Hitoshi; Ahn, J. K.*; Han, Y.*; Hasegawa, Shoichi; Hwang, S. H.*; Ichikawa, Yudai; Imai, Kenichi; Kiuchi, Ryuta*; Ozawa, Kyoichiro; et al.

Nuclear Instruments and Methods in Physics Research A, 763, p.65 - 81, 2014/11

 Times Cited Count:4 Percentile:59.64(Instruments & Instrumentation)

We developed a prototype TPC for an H-dibaryon search experiment at J-PARC. To investigate its performance, we conducted tests with Ar-CH$$_{4}$$ (90:10) and Ar-CF$$_{4}$$ (95:5), where the former is mainly used. The detection efficiency was measured to be 98% at the beam rate up to $$5times10^{5}$$ cps/cm$$^{2}$$, and 90% at the rate of $$3times10^{6}$$ cps/cm$$^{2}$$. Based on the measured horizontal resolution of 0.19-0.46 mm at the drift length of 5-20 cm, the position resolution of better than 0.3 mm is estimated in 1 T magnetic field. The ion backflow fraction was measured to be 5% and reduced up to 3% at the gain of $$1.6times10^{4}$$. The horizontal position distortion due to ion backflow in the gate operation was suppressed within $$pm 0.2$$ mm at the beam rates up to $$5times10^{5}$$ cps/cm$$^{2}$$. On the other hand, the distortion with the gate open was measured to be $$pm2$$ mm. The distortion in the final experiment is estimated to be $$0.3 pm 0.2$$ mm.

Journal Articles

Development of a GEM-TPC for H-dibaryon search experiment at J-PARC

Sako, Hiroyuki; Ahn, J. K.*; Baek, K. H.*; Bassalleck, B.*; Fujioka, H.*; Guo, L.*; Hasegawa, Shoichi; Hicks, K.*; Honda, R.*; Hwang, S. H.*; et al.

Journal of Instrumentation (Internet), 9(4), p.C04009_1 - C04009_10, 2014/04

 Times Cited Count:3 Percentile:79.22(Instruments & Instrumentation)

A TPC has been developed for J-PARC E42 experiment to search for H-dibaryon in ($$K^-$$, $$K^+$$) reaction. An event with 2 $$pi^-$$ and 2 protons decaying from H-dibaryon is searched for inside the TPC. The TPC has octagonal prism shape drift volume with about 50 cm diameter with 55 cm drift length filled with Ar-CH$$_{4}$$ (90:10) gas. At the end of the drift volume, 3-layer GEMs are equipped. In order to analyze momenta of produced particles, the TPC is applied with 1 T dipole magnetic field parallel to the drift electric field with a superconducting Helmholz magnet. In order to maximize the acceptance of H-dibaryon events, a diamond target is installed inside the TPC drift volume, in a cylindrical hole opened from the top to the middle of the drift volume. Since extremely high-rate $$K^-$$ beam is directly injected into the TPC drift volume to the target, a gating grid and GEMs are adopted to suppress positive-ion feedback.

Journal Articles

Search for $$^6_{Lambda}$$H hypernucleus by the $$^{6}$$Li($$pi^-,K^+$$) reaction at $$p_pi$$- = 1.2 GeV/$$c$$

Sugimura, Hitoshi; Imai, Kenichi; Sako, Hiroyuki; Sato, Susumu; Kiuchi, Ryuta; Ichikawa, Yudai; Hwang, S. H.*; Hasegawa, Shoichi; Tanida, Kiyoshi; J-PARC E10 Collaboration*

Physics Letters B, 729, p.39 - 44, 2014/02

 Times Cited Count:26 Percentile:10.88(Astronomy & Astrophysics)

We have carried out an experiment to search for a neutron-rich hypernucleus, $$^6_Lambda$$H, by the $$^{6}$$Li($$pi$$$$^{-}$$,K$$^{+}$$) reaction at p$$_{pi-}$$ = 1.2 GeV/c. The obtained missing-mass spectrum with an estimated energy resolution of 3.2 MeV (FWHM) showed no peak structure corresponding to the $$^6_Lambda$$H hypernucleus neither below nor above the $$^4_Lambda$$H+2n particle decay threshold. An upper limit of the production cross section for the bound $$^6_Lambda$$H hypernucleus was estimated to be 1.2 nb/sr at 90% confidence level.

Journal Articles

Search for the $$K^-pp$$ bound state via $$gamma d rightarrow K^+pi^- X$$ reaction at $$E_{gamma}$$ = 1.5 - 2.4 GeV

Tokiyasu, Atsushi*; Imai, Kenichi; Hwang, S. H.*; LEPS Collaboration*

Physics Letters B, 728, p.616 - 621, 2014/01

 Times Cited Count:51 Percentile:3.23(Astronomy & Astrophysics)

Journal Articles

$$K^{ast 0}Sigma^+$$ photoproduction with evidence for the Kappa Meson Exchange at SPring-8/LEPS

Hwang, S. H.*; Hicks, K.*; Ahn, J. K.*; Nakano, Takashi*

Few-Body Systems, 54(7-10), p.1037 - 1041, 2013/08

 Times Cited Count:0 Percentile:100(Physics, Multidisciplinary)

Journal Articles

Spin-density matrix elements for $$gamma p rightarrow K^{*0} Sigma^+$$ at $$E_{gamma} = 1.85 - 3.0$$ GeV with evidence for $$kappa (800)$$ meson exchange

Imai, Kenichi; Hwang, S. H.*; Hicks, K.*; LEPS Collaboration*

Physical Review Letters, 108(9), p.092001_1 - 092001_5, 2012/03

 Times Cited Count:18 Percentile:27.02(Physics, Multidisciplinary)

The exclusive reaction $$gamma p rightarrow K^{*0} Sigma^+ $$ was measured using lineraly polarized photon at $$E_{gamma} - 1.85 - 3.0$$ GeV. Angular distributions of the $$K^+pi^-$$ system were fitted to extract spin-density matrix elements of the $$K^{*0}$$ decay. The measured parity asymmetry shows that natural parity exchange is dominant in this reaction. This result clearly indicates the need for $$t$$-channel exchange of the $$kappa (800)$$ scalar exchange.

Journal Articles

Development of high power long-pulse RF transmitter for ICRF heating in fusion researches and cyclotron accelerator

Kwak, J. G.*; Wang, S. J.*; Bae, Y. D.*; Kim, S. H.*; Hwang, C. K.*; Moriyama, Shinichi

Fusion Engineering and Design, 86(6-8), p.938 - 941, 2011/10

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

KAERI have been developing the transmitters for ICRF heating for KSTAR and the cyclotron accelerator since 1996. The toroidal magnetic field of KSTAR is nominally 3 T so that 25-60 MHz transmitter is required to cover ICRF heating scenarios of the KSTAR. The first transmitter is operating up to 60 MHz and it succeeded in achieving 2 MW for 300 s in 2008. Up to 300 kW RF power was successfully injected to KSTAR plasmas. The second one is 70 kW/CW transmitter used for the cyclotron accelerator and their frequency range is from 25 to 50 MHz. Its engineering design was finished. The third one is 1 MW/VHF transmitter which was loaned from JAEA. As the operating ICRF frequency of KSTAR is lower, its cavity structure will be modified from 110 MHz to 60 MHz. The test results of 60 MHz and lessons from the high power test of 2 MW transmitter will be introduced and the circuit analysis and engineering design work for the second and third amplifiers will be shown.

Journal Articles

Hybridization between the conduction band and 3$$d$$ orbitals in the oxide-based diluted magnetic semiconductor In$$_{2-x}$$V$$_x$$O$$_3$$

Kobayashi, Masaki*; Ishida, Yukiaki*; Hwang, J. I.*; Song, G. S.*; Takizawa, Masaru*; Fujimori, Atsushi; Takeda, Yukiharu; Okochi, Takuo*; Okane, Tetsuo; Saito, Yuji; et al.

Physical Review B, 79(20), p.205203_1 - 205203_5, 2009/05

 Times Cited Count:7 Percentile:67.66(Materials Science, Multidisciplinary)

Journal Articles

Local electronic structure of Cr in the II-VI diluted ferromagnetic semiconductor Zn$$_{1-x}$$Cr$$_x$$Te

Kobayashi, Masaki*; Ishida, Yukiaki*; Hwang, J. I.*; Song, G. S.*; Fujimori, Atsushi; Yang, C. S.*; Lee, L.*; Lin, H.-J.*; Huang, D.-J.*; Chen, C. T.*; et al.

New Journal of Physics (Internet), 10, p.055011_1 - 055011_15, 2008/05

 Times Cited Count:11 Percentile:39.82(Physics, Multidisciplinary)

Journal Articles

Bulk-sensitive photoemission spectroscopy of $$A_{2}$$FeMoO$$_{6}$$ double perovskites ($$A$$=Sr, Ba)

Kang, J.-S.*; Kim, J. H.*; Sekiyama, Akira*; Kasai, Shuichi*; Suga, Shigemasa*; Han, S. W.*; Kim, K. H.*; Muro, Takayuki*; Saito, Yuji; Hwang, C.*; et al.

Physical Review B, 66(11), p.113105_1 - 113105_4, 2002/09

 Times Cited Count:62 Percentile:9.29(Materials Science, Multidisciplinary)

The electronic structures of Sr$$_{2}$$FeMoO$$_{6}$$ (SFMO) and Ba$$_{2}$$FeMoO$$_{6}$$ (BFMO) double perovskites have been investigated using Fe 2p-3d resonant photoemission spectroscopy (PES) and the Cooper minimum in the Mo 4d photoionization cross section. The states close to the Fermi level are found to have a strongly mixed Mo–Fe t$$_{2g}$$ character, indicating that the Fe valence is far from pure 3+. The Fe 2p$$_{3/2}$$ x-ray absorption spectroscopy spectra reveal the mixed-valent Fe $$^{3+}$$–Fe$$^{2+}$$ configurations, and a larger Fe$$^{2+}$$ component for BFMO than for SFMO, suggesting an operative double exchange interaction. The valence-band PES spectra reveal good agreement with the local-spin-density-approximation (LSDA+U) calculation.

Oral presentation

Developments of gate functioning used GEM

Sato, Susumu; Sako, Hiroyuki; Hasegawa, Shoichi; Sugimura, Hitoshi; Ichikawa, Yudai; Ozawa, Kyoichiro; Kiuchi, Ryuta*; Hwang, S. H.*; Imai, Kenichi

no journal, , 

no abstracts in English

Oral presentation

Search for H-dibaryon in ($$K^{-}$$,$$K^{+}$$) reaction at J-PARC, 1

Sako, Hiroyuki; Imai, Kenichi; Sato, Susumu; Hasegawa, Shoichi; Hwang, S. H.*; Sugimura, Hitoshi; Ichikawa, Yudai; Tanida, Kiyoshi; Kiuchi, Ryuta*; Ahn, J. K.*; et al.

no journal, , 

The H-dibaryon has been proposed as a stable 6-quark sate, and various experiments have been performed to search for it, but never been successful. KEK-PS E224 and E522 experiments observed peaks near the $$Lambda$$ $$Lambda$$ threshold in the invariant mass spectra although statistics is not enough. On the other hand, recent lattice QCD calculations predict the H is a shallow bound state or a resonance state. We proposed J-PARC E42 experiment to search for the H-dibaryon in ($$K^{+}$$,$$K^{-}$$) reaction with two-order higher statistics and higher mass resolutions.

Oral presentation

Development of hypTPC for H-dibaryon search experiment at J-PARC

Imai, Kenichi; Hwang, S. H.*

no journal, , 

Oral presentation

Development of the Monte-Carlo simulation for E42 experiment

Imai, Kenichi; Hwang, S. H.*

no journal, , 

Oral presentation

Development of Hyperon Time-Projection-Chamber (HypTPC) for J-PARC E42

Imai, Kenichi; Hwang, S. H.*

no journal, , 

Oral presentation

Development of KURAMA spectrometer at J-PARC K1.8 beamline

Imai, Kenichi; Hwang, S. H.*

no journal, , 

Oral presentation

Development of TPC for J-PARC-E42 experiment; Performance evaluation of a prototype TPC in the magnetic field and development of large area GEMs

Sako, Hiroyuki; Imai, Kenichi; Sato, Susumu; Hasegawa, Shoichi; Hwang, S. H.*; Sugimura, Hitoshi; Ichikawa, Yudai; Tanida, Kiyoshi; Kiuchi, Ryuta*

no journal, , 

J-PARC E42 is an experiment to search for the H-dibaryon in ($$K^{-}$$,$$K^{+}$$) reactions. The experimental setup consists of a larget solid angle TPC, a Helmholtz dipole magnet, and a $$K^{+}$$ spectrometer (Kurama). We have performed an experiment of a prototype TPC injecting a UV laser under magnetic field with the FM magnet in the J-PARC hadron facility hall. We have been also developing the second TPC which has the real size the pad plane and GEMs. In this presentation, we report the results of the prototype TPC and the status for the second TPC.

29 (Records 1-20 displayed on this page)