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Journal Articles

Production and decay of charmed baryons

Hosaka, Atsushi; Hiyama, Emiko; Kim, S.-H.*; Kim, H.-C.*; Nagahiro, Hideko*; Noumi, Hiroyuki*; Oka, Makoto; Shirotori, Kotaro*; Yoshida, Tetsuya*; Yasui, Shigehiro*

Nuclear Physics A, 954, p.341 - 351, 2016/10

https://doi.org/10.1016/j.nuclphysa.2016.05.009
 Times Cited Count：3 Percentile：26.8(Physics, Nuclear)

In this paper, we discuss reactions involving charmed baryons to explore their unique features. A well known phenomenon, the separation of the two internal motions of the $$rho$$ and $$lambda$$ types of a three-quark system is revisited. First we discuss the mass spectrum of low-lying excitations as functions of the heavy quark mass, smoothly connecting the $$SU(3)$$ and heavy quark limits. The properties of these modes can be tested in the production and decay reactions of the baryons. For the productions, we consider a one step process which excites dominantly $$lambda$$ mode excitations. We find abundant production rates for some of excited states. For decays, we study pion emission process, which provides a clean tool to test the structure of heavy quark systems due to well controlled low energy dynamics of the pion and quark. Both productions and decays of the charmed baryons are the issues of the future experiments at J-PARC.

Journal Articles

Charmed baryon spectroscopy experiment at J-PARC

Shirotori, Kotaro*; Tanida, Kiyoshi; 19 of others*

JPS Conference Proceedings (Internet), 8, p.022012_1 - 022012_6, 2015/09

https://doi.org/10.7566/JPSCP.8.022012

Journal Articles

Precise determination of $$^{12}_{Lambda}$$C level structure by $$gamma$$-ray spectroscopy

Hosomi, Kenji; Ma, Y.*; Ajimura, Shuhei*; Aoki, Kanae*; Dairaku, Seishi*; Fu, Y.*; Fujioka, Hiroyuki*; Futatsukawa, Kenta*; Imoto, Wataru*; Kakiguchi, Yutaka*; et al.

Progress of Theoretical and Experimental Physics (Internet), 2015(8), p.081D01_1 - 081D01_8, 2015/08

https://doi.org/10.1093/ptep/ptv113
 Times Cited Count：14 Percentile：66.59(Physics, Multidisciplinary)

Level structure of the $$^{12}_{Lambda}$$C hypernucleus was precisely determined by means of $$gamma$$-ray spectroscopy. We identified four $$gamma$$-ray transitions via the $$^{12}$$C$$(pi^{+},K^{+}gamma)$$ reaction using a germanium detector array, Hyperball2. The spacing of the ground-state doublet $$(2^{-}, 1^{-}_{1})$$ was measured to be $$161.5pm0.3$$(stat)$$pm0.3$$ (syst)keV from the direct $$M1$$ transition. Excitation energies of the $$1^{-}_{2}$$ and $$1^{-}_{3}$$ states were measured to be $$2832pm3pm4$$, keV and $$6050pm8pm7$$, keV, respectively. The obtained level energies provide definitive references for the reaction spectroscopy of $$Lambda$$ hypernuclei.

Journal Articles

Superdeformation in $$^{35}$$S

Go, Shintaro*; Ideguchi, Eiji*; Yokoyama, Rin*; Kobayashi, Motoki*; Kisamori, Keiichi*; Takaki, Motonobu*; Miya, Hiroyuki*; Ota, Shinsuke*; Michimasa, Shinichiro*; Shimoura, Susumu*; et al.

JPS Conference Proceedings (Internet), 6, p.030005_1 - 030005_4, 2015/06

https://doi.org/10.7566/JPSCP.6.030005

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

https://doi.org/10.1016/j.nima.2014.06.007
 Times Cited Count：5 Percentile：38.03(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

https://doi.org/10.1088/1748-0221/9/04/C04009
 Times Cited Count：3 Percentile：16.04(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 $$Theta^+$$ via the pion induced reaction at J-PARC; J-PARC E19

Shirotori, Kotaro

Few-Body Systems, 54(1-4), p.145 - 150, 2013/03

https://doi.org/10.1007/s00601-012-0367-5
 Times Cited Count：0 Percentile：0(Physics, Multidisciplinary)

The $$Theta^+$$ pentaquark baryon was searched for via the $$pi^-prightarrow K^-X$$ reaction at J-PARC. $$pi^-$$ meson beams were irradiated on the liquid hydrogen target with the beam momentum of 1.92 GeV/$$c$$. In the missing mass spectrum, no peak structure corresponding to $$Theta^{+}$$ mass was observed. The preliminary upper limit of the differential cross section averaged over the scattering angle of 2$$^{circ}$$ to 15$$^{circ}$$ at the laboratory frame was less than 0.3 $$mu$$b/sr at the 90% confidence level in the missing mass region over 1.51 GeV/$$c^2$$ to 1.55 GeV/$$c^2$$.

Journal Articles

Search for the $$Theta^{+}$$ pentaquark via the $$pi^-prightarrow K^-X$$ reaction at 1.92 GeV/$$c$$

Shirotori, Kotaro; Imai, Kenichi; Sako, Hiroyuki; Sato, Susumu; 64 of others*

Physical Review Letters, 109(13), p.132002_1 - 132002_5, 2012/09

https://doi.org/10.1103/PhysRevLett.109.132002

The $$Theta^+$$ pentaquark baryon was searched for via the $$pi^-prightarrow K^-X$$ reaction in a missing-mass resolution of 1.4 MeV/$$c^2$$ (FWHM) at J-PARC. $$pi^-$$ meson beams were incident on the liquid hydrogen target with the beam momentum of 1.92 GeV/$$c$$. No peak structure corresponding to the $$Theta^+$$ mass was observed. The upper limit of the production cross section averaged over the scattering angle of 2$$^{circ}$$ to 15$$^{circ}$$ in the laboratory frame was obtained to be 0.26 $$mu$$b/sr in the mass region of 1.51$$-$$1.55 GeV/$$c^2$$. The upper limit of the $$Theta^+$$ decay width using the effective Lagrangian approach was obtained to be 0.72 MeV/$$c^2$$ and 3.1 MeV/$$c^2$$ for $$J^P_{Theta}=1/2^+$$ and $$J^P_{Theta}= 1/2^-$$, respectively.

Journal Articles

Search for the $$Theta^+$$ pentaquark via $$pi^-p rightarrow K^-X$$ reaction at 1.92 GeV/$$c$$

Shirotori, Kotaro*; Imai, Kenichi; Sako, Hiroyuki; Sato, Susumu; Sugimura, Hitoshi; Ichikawa, Yudai; Tanida, Kiyoshi; 61 of others*

Physical Review Letters, 109(13), p.132002_1 - 132002_5, 2012/09

https://doi.org/10.1103/PhysRevLett.109.132002
 Times Cited Count：31 Percentile：79.11(Physics, Multidisciplinary)

The $$Theta^+$$ pentaquark baryon was searched for via the $$pi^-p rightarrow K^-X$$ reaction at 1.92 GeV/$$c$$ with a missing mass resolution of 1.4 MeV/c$$^2$$ (FWHM) at J-PARC. No peak structure corresponding to the $$Theta^+$$ mass was observed. The upper limit of the production cross section is obtained to be 0.26$$mu$$b/sr in the pentaquark mass region.

Oral presentation

Search for $$Theta^+$$ penta-quark baryon at the J-PARC K1.8 beam line; First result and current status

Shirotori, Kotaro

no journal, , 

An observation of the $$Theta^+$$ pentaquarck baryon which consists of five quarks was firstly reported by the LEPS collaboration in 2003. The LEPS report triggered the investigation of $$Theta^+$$. Several experiments reported both positive and negative results. Therefore, the existence of $$Theta^+$$ has been not confirmed. The J-PARC E19 experiment was performed at the J-PARC K1.8 beam line in 2010. The purpose of experiment is to search for $$Theta^+$$ using the SKS system. The missing mass resolution of the system was 1.4 MeV/$$c^2$$ (FWHM) by which the highest sensitivity can be achieved. We irradiated $$pi^-$$ mesons on the liquid hydrogen target with the beam momentum of 1.92 GeV/$$c$$. In the missing mass spectrum, any prominent structure corresponding to $$Theta^+$$ was not observed. The upper limit of the cross section was obtained to be less than 200 nb. The experimental result gives a strong constraint to the existence of $$Theta^+$$.

Oral presentation

Search for $$Theta^+$$ via the pion induced reaction at J-PARC; J-PARC E19

Shirotori, Kotaro

no journal, , 

An observation of the $$Theta^+$$ pentaquark which consists of five quarks was firstly reported by the LEPS collaboration in 2003. However, the existence of $$Theta^+$$ has been not confirmed. The 1st step of the J-PARC E19 experiment was performed at the J-PARC K1.8 beam line in 2011. The purpose of the experiment is to search for $$Theta^+$$ in the $$p(pi^-, K^-)$$ reaction using the K1.8 beam line spectrometer and the SKS system. The missing mass resolution using both systems was 1.4 MeV/$$c^2$$ (FWHM) by which the highest sensitivity could be achieved. We irradiated $$pi^-$$ mesons on the liquid hydrogen target with the beam momentum of 1.92 GeV/$$c$$. In the missing mass spectrum, any peak structure corresponding to $$Theta^+$$ mass was not observed. The upper limit of the cross section was obtained to be less than 0.3 $$mu$$b.

Oral presentation

Design of spectrometer for H-dibaryon search at J-PARC

Sako, Hiroyuki; Imai, Kenichi; Sato, Susumu; Sugimura, Hitoshi; Ichikawa, Yudai; Hasegawa, Shoichi; Shirotori, Kotaro; Kiuchi, Ryuta*; Honda, Ryotaro

no journal, , 

Recent Lattice-QCD calculations show the baryon-baryon potential corresponding to the H-dibaryon is attactive, and predicts H-dibaryon is either a weakly bound state or a resonance state. On the other hand, KEK-E224, E522 experiments observed a peak near the $$LambdaLambda$$ invariant mass spectrum, which suggests existence of H-dibaryon. However, due to low statistics and low mass resolution, they did not discover the evidence for H-dibaryon. We propose an experiment (P-42) to search for H-dibaryon at J-PARC with $$10^{6}$$ Kaon beams with improved statistics and mass resolutions. In this experiment, a dipole magnet spectrometer based on high-rate capable GEM-TPC is designed to reconstruct 2 protons and to 2 $$pi^{-}$$s decaying from a H-dibaryon.

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