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論文

Missing-mass measurement of the $$^{12}$$C$$(K^-,K^+)$$ reaction at 1.8 GeV/$$c$$ 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

https://doi.org/10.1093/ptep/ptae133
 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 $$^{12}$$C$$(K^-, K^+)$$ reaction at an incident beam momentum of 1.8 GeV/$$c$$. 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 $$^{12}_{Xi}$$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 $$sigma$$ being held constant. The peak positions were obtained to be $$B_{Xi} = 8.9 pm 1.4$$ (stat.) $$^{+3.8}_{-3.1}$$ (syst.) MeV and $$B_{Xi} = -2.4 pm 1.3$$ (stat.) $$^{+2.8}_{-1.2}$$ (syst.) MeV. Another model assumption, utilizing quasi-free (QF) and one Breit-Wigner function with $$B_{Xi} = -2.7 pm 2.2$$ (stat.) $$^{+0.5}_{-0.7}$$ (syst.) MeV and $$Gamma = 4.1 pm 2.1$$ (stat.) $$^{+1.2}_{-0.7}$$ (syst.) MeV, also yielded a similar $$chi^2$$ value.

論文

Measurement of differential cross sections for $$Sigma^+ p$$ 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

https://doi.org/10.1093/ptep/ptac101
 被引用回数：16 パーセンタイル：83.97(Physics, Multidisciplinary)

We performed a novel $$Sigma^+p$$ scattering experiment at the J-PARC Hadron Experimental Facility. Approximately 2400 $$Sigma^+p$$ elastic scattering events were identified from $$4.9 times 10^7$$ tagged $$Sigma^+$$ particles in the $$Sigma^+$$ momentum range 0.44 - 0.80 GeV/c. The differential cross sections of the $$Sigma^+p$$ 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 $$^3S_1$$ and $$^1P_1$$ 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 $$20^circ<|delta_{^3S_1}|<35^circ$$. If the sign of $$delta_{^3S_1}$$ is assumed to be negative, the interaction in this channel is moderately repulsive, as the Nijmegen extended-sort-core models predicted.

論文

First observation of a nuclear $$s$$-state of a $$Xi$$ hypernucleus, $$^{15}_{Xi}{rm C}$$

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

https://doi.org/10.1093/ptep/ptab073
 被引用回数：21 パーセンタイル：81.08(Physics, Multidisciplinary)

Bound-systems of $$Xi^-$$-$$^{14}_{}{rm N}$$ are studied via $$Xi^-$$ capture at rest followed by emission of a twin single-$$Lambda$$ hypernucleus in the emulsion detectors. Two events forming extremely deep $$Xi^-$$ 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 $$Xi^-+^{14}_{}{rm N}to^{5}_{Lambda}{rm He}$$+$$^{5}_{Lambda}{rm He}$$+$$^{4}_{}{rm He}$$+$$n$$. Since there are no excited states for daughter particles, the binding energy of the $$Xi^-$$ hyperon, $$B_{Xi^-}$$, in $$^{14}_{}{rm N}$$ nucleus was uniquely determined to be 6.27 $$pm$$ 0.27 MeV. Another $$Xi^-$$-$$^{14}_{}{rm N}$$ system via the decay $$^{9}_{Lambda}{rm Be}$$ + $$^{5}_{Lambda}{rm He}$$ + $$n$$ brings a $$B_{Xi^-}$$ value, 8.00 $$pm$$ 0.77 MeV or 4.96 $$pm$$ 0.77 MeV, where the two possible values of $$B_{Xi^-}$$ correspond to the ground and the excited states of the daughter $$^{9}_{Lambda}{rm Be}$$ nucleus, respectively. Because the $$B_{Xi^-}$$ values are larger than those of the previously reported events (KISO and IBUKI), which are both interpreted as the nuclear $$1p$$ state of the $$Xi^-$$-$$^{14}_{}{rm N}$$ system, these new events give the first indication of the nuclear $$1s$$ state of the $$Xi$$ hypernucleus, $$^{15}_{Xi}{rm C}$$.

論文

Observation of Coulomb-assisted nuclear bound state of $$Xi^-$$-$$^{14}$$N system

早川 修平; 藤田 真奈美; 長谷川 勝一; 橋本 直; 細見 健二; 市川 裕大; 今井 憲一*; 七村 拓野; 成木 恵; 佐甲 博之; et al.

Physical Review Letters, 126(6), p.062501_1 - 062501_6, 2021/02

https://doi.org/10.1103/PhysRevLett.126.062501
 被引用回数：45 パーセンタイル：93.51(Physics, Multidisciplinary)

In an emulsion-counter hybrid experiment performed at J-PARC, a $$Xi^-$$ absorption event was observed which decayed into twin single-$$Lambda$$ hypernuclei. Kinematic calculations enabled a unique identification of the reaction process as $$Xi^{-} + ^{14}$$N$$ rightarrow ^{10}_Lambda$$Be + $$^5_Lambda$$He. For the binding energy of the $$Xi^{-}$$ hyperon in the $$Xi^-$$-$$^{14}$$N system a value of $$1.27 pm 0.21$$ MeV was deduced. The energy level of $$Xi^-$$ is likely a nuclear $$1p$$ state which indicates a weak $${Xi}N$$-$$LambdaLambda$$ coupling.

論文

Study on the baryon interaction by $$Xi$$ hypernuclear spectroscopy with the $$(K^-, K^+)$$ reaction

後神 利志*; 藤田 真奈美; 長谷川 勝一; 細見 健二; 今井 憲一*; 市川 裕大; 七村 拓野; 成木 恵; 佐甲 博之; 佐藤 進; et al.

Journal of Physics; Conference Series, 1643, p.012133_1 - 012133_6, 2020/12

BB2021-0622.pdf:0.71MB

https://doi.org/10.1088/1742-6596/1643/1/012133
 被引用回数：2 パーセンタイル：78.92(Astronomy & Astrophysics)

We performed $$Xi$$ hypernuclear spectroscopy with the $$(K^-, K^+)$$ reaction at J-PARC to investigate the $$Xi N$$ interaction (J-PARC E05). A new experiment (J-PARC E70) in which a better energy resolution could be achieved is now being prepared. In this article, an analysis status of J-PARC E05 and a preparation status of J-PARC E70 are described.

論文

Search for excited state of $$_{Sigma }^{4}{rm He}$$ hypernucleus in the J-PARC E13 experiment

中川 真菜美*; 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; 田村 裕和; 谷田 聖; et al.

JPS Conference Proceedings (Internet), 26, p.023005_1 - 023005_3, 2019/11

https://doi.org/10.7566/JPSCP.26.023005

The $$Sigma N$$ interaction is not much studied than the $$Lambda N$$ interaction. To understand the $$Sigma N$$ interaction, we study $$Sigma$$ hypernuclei. As for the $$Sigma$$ hypernucleus, only the ground state of $$_{Sigma }^{4}{rm He}$$ has been observed. To obtain more information about the $$Sigma N$$ interaction, the excited state should be studied. Therefore, we measure the missing-mass of the $$^4$$He$$(K^-,pi^-)$$ reaction at $$p_{K^-} = 1.5$$ GeV/$$c$$ and $$theta_{rm Lab} =$$ 2-14$$^{circ}$$ at the J-PARC K1.8 beam line. The ground state of $$_{Sigma }^{4}{rm He}$$ is observed whereas a peak of the excited states is not observed. We also observe suppression of the $$Sigma$$ quasi-free process at smaller angles.

論文

First $$gamma$$-ray spectroscopy of an $$sd$$-shell hypernucleus, $$^{19}_{Lambda}$$F

Yang, S. B.*; 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; 田村 裕和*; 谷田 聖; et al.

JPS Conference Proceedings (Internet), 26, p.023015_1 - 023015_5, 2019/11

https://doi.org/10.7566/JPSCP.26.023015

We performed a gamma-ray spectroscopy of $$({}_{Lambda}^{19}{rm F})$$ at J-PARC Hadron Experimental Facility in 2015. It is the first measurement of $$gamma$$ rays emitted from $$sd$$-shell hypernuclei. In this experiment, we determined the energy spacing between the ground state spin doublet, $$3/2^+$$ and $$1/2^+$$ states, as 316 keV. The excitation energies of $$5/2^+$$ and $$1/2^+$$ states are also determined to be 895 and 1266 keV, respectively. The energy spacing is found to be well reproduced by shell-model calculations which describe $$s$$- and $$p$$-shell $$Lambda$$ hypernuclei well. The results show that the present theories of the $$Lambda N$$ interaction describe not only the light hypernuclei but also a heavier hypernucleus.

論文

Gamma-ray spectroscopy of single $$Lambda$$-hypernuclei at J-PARC; Results and perspective

小池 武志*; 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; 杉村 仁志; 田村 裕和; et al.

AIP Conference Proceedings 2130, p.020011_1 - 020011_9, 2019/07

https://doi.org/10.1063/1.5118379
 被引用回数：2 パーセンタイル：69.74(Physics, Nuclear)

Experimental results from the J-PARC E13 experiments are summarized. A new experimental set up of E13 has established a platform for the future $$gamma$$-ray hypernuclear spectroscopy at J-PARC using kaon beams. New $$gamma$$ rays are identified in $$^4_{Lambda}$$He and $$^{19}_{Lambda}$$F. The energy of 1.406 MeV for the $$^4_{Lambda}$$He$$(1^+ to 0^+)$$ transition confirmed a sizable effect of Charge Symmetry Breaking (CSB) in $$Lambda N$$ interaction in the $$A=4$$ hypernuclear system. The identification of four $$gamma$$ rays in $$^{19}_{Lambda}$$F is made for the first time in $$sd$$ shell hypernuclei. Especially, energy spacing of the ground state doublet is found to be 315.5 keV. A good agreement with two theoretical calculations suggests that the theoretical formalism used in $$p$$ shell hypernuclei is also applicable to heavier hypernuclei. Lastly, an overview of the future J-PARC E63 experiment is given.

論文

Observation of a $$Xi$$ bound state in the $$^{12}$$C$$(K^-, K^+)$$ reaction at 1.8 GeV/$$c$$

永江 知文*; 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; 金原 慎二; 七村 拓野*; 成木 恵; et al.

AIP Conference Proceedings 2130, p.020015_1 - 020015_9, 2019/07

https://doi.org/10.1063/1.5118383
 被引用回数：12 パーセンタイル：97.60(Physics, Nuclear)

For the full understanding of baryon-baryon interactions in flavor $$SU(3)$$, the $$Xi N$$ interaction is the last missing piece of information. So far, we have revealed the $$Lambda N$$ interaction to be attractive ($$U_{Lambda} cong 30$$ MeV), and $$Sigma N$$ interaction to be repulsive in the medium to heavy mass-number region. The $$Lambda Lambda$$ bonding energy is weakly attractive. While we have a few experimental observations suggesting the $$Xi N$$ interaction would be attractive, there still exist large theoretical ambiguities weather it is attractive or not. Experimental determinations on the existence of bound states of $$Xi$$ hypernuclei by observing bound-state peaks are strongly awaited. In this report, a new preliminary result on the missing-mass spectrum of a $$^{12}$$C$$(K^-, K^+)$$ reaction, which strongly suggests the existence of $$Xi$$-hypernuclear bound states, is presented.

論文

Observation of a Be double-Lambda hypernucleus in the J-PARC E07 experiment

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

https://doi.org/10.1093/ptep/pty149
 被引用回数：31 パーセンタイル：82.94(Physics, Multidisciplinary)

A double-$$Lambda$$ hypernucleus, $${}_{LambdaLambda}mathrm{Be}$$, was observed by the J-PARC E07 collaborationin nuclear emulsions tagged by the $$(K^{-},K^{+})$$ reaction. This event was interpreted as a production and decay of $$ {}_{LambdaLambda}^{;10}mathrm{Be}$$,$${}_{LambdaLambda}^{;11}mathrm{Be}$$, or $${}_{LambdaLambda}^{;12}mathrm{Be}^{*}$$ via $$Xi^{-}$$ capture in $${}^{16}mathrm{O}$$.By assuming the capture in the atomic 3D state, the binding energy of two $$Lambda$$ hyperons$$,$$($$B_{LambdaLambda}$$)of these double-$$Lambda$$ hypernuclei are obtained to be$$15.05 pm 0.11,mathrm{MeV}$$, $$19.07 pm 0.11,mathrm{MeV}$$, and $$13.68 pm 0.11,mathrm{MeV}$$, respectively. Based on the kinematic fitting, $${}_{LambdaLambda}^{;11}mathrm{Be}$$ is the most likely explanation for the observed event.

論文

Charge identification of low-energy particles for double-strangeness nuclei in nuclear emulsion

金原 慎二*; 江川 弘行; 早川 修平; 吉田 純也; 他12名*

Progress of Theoretical and Experimental Physics (Internet), 2019(1), p.011H01_1 - 011H01_9, 2019/01

https://doi.org/10.1093/ptep/pty137
 被引用回数：6 パーセンタイル：37.62(Physics, Multidisciplinary)

ダブルハイパー核の崩壊から放出された核種を識別してその親核種を同定するため、電荷1から5までの核種を識別する技術を開発した。この方法は基本的には原子核乾板中の飛跡体積を測定するもので、その太さ、乾板の表面からの深さ、角度を、$$^{1}$$H, $$^{4}$$He, $$^{7}$$Li, $$^{9}$$Be, $$^{11}$$Bについて理研RIBFで照射したサンプルについて評価した。$$alpha$$線を用いた較正ののち、$$alpha$$線飛跡との体積比を用いて5種類の電荷を識別する二次関数の関係式を得た。この手法を、過去に検出された複数解釈のあるグザイハイパー核候補について、その識別に用いた。その結果、シングルラムダハイパー核の崩壊の娘粒子の一つを、尤度比0.9で$$^{6}$$Heと識別した。そして、この事象は$$Xi$$$$^{-}$$ + $$^{14}$$N $$rightarrow$$ $$_{Lambda}$$$$^{9}$$Be + $$_{Lambda}$$$$^{5}$$He + $$n$$と一意に同定された。

論文

First determination of the level structure of an $$sd$$-shell hypernucleus, $$^{19}_{Lambda}$$F

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(13), p.132505_1 - 132505_5, 2018/03

AA2018-0124.pdf:0.62MB

https://doi.org/10.1103/PhysRevLett.120.132505
 被引用回数：9 パーセンタイル：53.40(Physics, Multidisciplinary)

We report on the first observation of $$gamma$$ rays emitted from an $$sd$$-shell hypernucleus, $$^{19}_{Lambda}$$F. The energy spacing between the ground state doublet, $$1/2^+$$ and $$3/2^+$$ states, of $$^{19}_{Lambda}$$F is determined to be $$315.5pm0.4({rm stat.})^{+0.6}_{-0.5}({rm syst.})$$ keV by measuring the $$gamma$$-ray energy of the $$M1(3/2^+ to 1/2^+)$$ transition. In addition, three $$gamma$$-ray peaks are observed and assigned as $$E2(5/2^+ to 1/2^+)$$, $$E1(1/2^- to 1/2^+)$$, and $$E1(1/2^- to 3/2^+)$$ transitions. The excitation energies of the $$5/2^+$$ and $$1/2^-$$ states are determined to be $$895.2pm0.3({rm stat.})pm0.5({rm syst.})$$ keV and $$1265.6pm1.2({rm stat.})^{+0.5}_{-0.7}({rm syst.})$$ keV, respectively. It is found that the ground state doublet spacing is well described by theoretical models based on existing $$s$$- and $$p$$-shell hypernuclear data.

論文

Spectroscopy of nuclei with multi-strangeness by using new S-2S spectrometer at J-PARC

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

https://doi.org/10.7566/JPSCP.18.011031

The missing mass spectroscopy of $$Xi^-$$ hypernuclei is planned at the Japan Proton Accelerator Research Complex (J-PARC) by using the $$(K^-,K^+)$$ reaction. We are constructing a new magnetic spectrometer, S-2S, which has a better momentum resolution [$$Delta p/p = 5 times 10^{-4}$$ (FHWM)] than that of an existing spectrometer (SKS) at J-PARC. S-2S would give us an opportunity to confirm the existence of $$Xi^-$$ 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.

論文

$$gamma$$-ray spectroscopy of hypernuclei; Recent results and prospect at J-PARC

田村 裕和*; 江川 弘行; 長谷川 勝一; 早川 修平; 細見 健二; Hwang, S.; 市川 裕大; 今井 憲一; 佐甲 博之; 佐藤 進; et al.

JPS Conference Proceedings (Internet), 17, p.011004_1 - 011004_11, 2017/07

https://doi.org/10.7566/JPSCP.17.011004

The present status and future prospects of precision $$gamma$$-ray spectroscopy of $$Lambda$$ hypernuclei are described. A new experiment (J-PARC E13) has been performed at the J-PARC K1.8 line employing a newly-developed germanium (Ge) detector array, Hyperball-J, via the $$(K^-,pi^-)$$ reaction on $$^4$$He and $$^{19}$$F targets. This is the first study of $$s$$-shell and $$sd$$-shell $$Lambda$$ hypernuclei with Ge detectors. The $$^4$$He target spectrum exhibited a $$gamma$$-ray peak of $$^4_{Lambda}{rm He}(1^+to 0^+)$$ at $$1.406 pm 0.002 pm 0.002$$ MeV. Compared with the energy ($$1.09 pm 0.02$$ MeV) of the corresponding transition for the mirror hypernucleus, $$^4_{Lambda}{rm H}(1^+to 0^+)$$, the present result clearly indicates a large charge symmetry breaking (CSB) effect. This decisive data for CSB allows a stringent test of baryon-baryon interaction models. As for the $$^{19}$$F target run, a preliminary spectrum shows several $$gamma$$-ray peaks assigned to $$^{19}_{Lambda}{rm F}$$ transitions. Future plans of $$gamma$$-ray spectroscopy are also discussed.

論文

The First gamma-ray spectroscopic study of $$sd$$-shell hypernucleus, $$^{19}_{Lambda}$$F

Yang, S. B.*; 江川 弘行; 長谷川 勝一; 早川 修平; 細見 健二; Hwang, S.; 市川 裕大; 今井 憲一; 佐甲 博之; 佐藤 進; et al.

JPS Conference Proceedings (Internet), 17, p.012004_1 - 012004_4, 2017/07

https://doi.org/10.7566/JPSCP.17.012004

The first $$gamma$$-ray spectroscopy of $$sd$$-shell hypernucleus, $$^{19}_{Lambda}$$F, is performed in June, 2015 at the J-PARC K1.8 beam line (J-PARC E13). Precise energy levels of $$^{19}_{Lambda}$$F can be revealed by measured $$gamma$$ rays in this experiment. Especially, the strength of $$Lambda N$$ spin-spin interaction in $$sd$$-shell hypernucleus is obtained through the energy spacing of the ground-state doublet of the hypernucleus. By comparing its strength between the $$s$$, $$p$$, and $$sd$$-shell hypernuclei, a radial dependence $$Lambda N$$ interaction is investigated. The hypernucleus is produced through the $$(K^-,pi^-)$$ reaction with the beam momentum of 1.8 GeV/c. In very preliminary results, we observed two $$gamma$$ rays, and their energies are $$315.8 pm 0.4$$ keV and $$ 895.3 pm 0.3$$ keV where the uncertainties are only statistical.

論文

Search for excited state of $$Sigma$$ hypernucleus in the J-PARC E13 experiment

中川 真菜美*; 江川 弘行; 長谷川 勝一; 早川 修平; 細見 健二; Hwang, S.; 市川 裕大; 今井 憲一; 佐甲 博之; 佐藤 進; et al.

JPS Conference Proceedings (Internet), 17, p.012009_1 - 012009_4, 2017/07

https://doi.org/10.7566/JPSCP.17.012009

One of the main items of the J-PARC E13 experiment is the search for excited states of the $$^4_{Sigma}$$He hypernucleus via the $$^4$$He$$(K^-,pi^-)$$ reaction at 1.5 GeV/c. The missing-mass spectrum of the $$^4$$He$$(K^-,pi^-)X$$ reaction was obtained in an angular range from 0 to 20 degrees. We show the count-base spectrum of the missing-mass in the angular range from 2 to 14 degrees. The ground state of $$^4_{Lambda}$$He and $$^4_{Sigma}$$He were clearly observed in the missing-mass spectrum. We also show three missing-mass spectra divided by the reaction angle.

論文

Missing-mass spectroscopy with the $$^6$$Li$$(pi^-,K^+)X$$ reaction to search for $$^6_Lambda$$H

本多 良太郎*; 長谷川 勝一; 早川 修平; 細見 健二; 市川 裕大; 今井 憲一; 永宮 正治; 佐甲 博之; 佐藤 進; 杉村 仁志; et al.

Physical Review C, 96(1), p.014005_1 - 014005_23, 2017/07

AA2017-0465.pdf:1.08MB

https://doi.org/10.1103/PhysRevC.96.014005
 被引用回数：14 パーセンタイル：69.51(Physics, Nuclear)

We searched for the bound state of the neutron-rich $$Lambda$$-hypernucleus $$^6_Lambda$$H, using the $$^6$$Li$$(pi^-,K^+)X$$ double charge-exchange reaction at a $$pi^-$$ beam momentum of 1.2 GeV/$$c$$ at J-PARC. A total of $$1.4 times 10^{12}$$ $$pi^-$$ was driven onto a $$^6$$Li target of 3.5 g/cm$$^2$$ thickness. No event was observed below the bound threshold, i.e., the mass of $$^4_Lambda$$H+$$2n$$, in the missing-mass spectrum of the $$^6$$Li$$(pi^-,K^+)X$$ reaction in the $$2^{circ} < theta_{pi K} <20^{circ}$$ angular range. Furthermore, no event was found up to 2.8 MeV/c$$^2$$ above the bound threshold.

論文

Observation of $$Xi$$ bound states in the $$^{12}$$C$$(K^-,K^+)X$$ reaction at 1.8 GeV/$$c$$ in J-PARC

永江 知文*; 江川 弘行; 長谷川 勝一; 細見 健二; 市川 裕大; 今井 憲一; 佐甲 博之; 佐藤 進; 杉村 仁志; 谷田 聖; et al.

Proceedings of Science (Internet), 281, p.038_1 - 038_7, 2017/05

https://doi.org/10.22323/1.281.0038

We have carried out a pilot data taking of the J-PARC E05 experiment to search for the bound state peaks of $$^{12}_{Xi}$$Be in the $$^{12}$$C$$(K^-,K^+)X$$ reaction at 1.8 GeV/$$c$$. The measurement was performed at the K1.8 beam line of the J-PARC hadron experimental hall with a typical $$K^-$$ beam intensity of $$6 times 10^5$$ every six seconds. So far the best energy resolution of about 6 MeV FWHM was achieved with the existing SKS spectrometer. With a reasonable statistics, we have succeeded to observe peak structures in the bound region, which seems to suggest that the potential depth of $$Xi$$ would be deeper than 14 MeV estimated in the previous measurements.

論文

Observation of spin-dependent charge symmetry breaking in $$Lambda N$$ interaction; $$gamma$$-ray spectroscopy of $$^4_{Lambda}$$He

山本 剛史*; 長谷川 勝一; 早川 修平; 細見 健二; Hwang, S.; 市川 裕大; 今井 憲一; 金原 慎二; 中田 祥之; 佐甲 博之; et al.

Physical Review Letters, 115(22), p.222501_1 - 222501_5, 2015/11

AA2015-0707.pdf:0.5MB

https://doi.org/10.1103/PhysRevLett.115.222501
 被引用回数：74 パーセンタイル：92.32(Physics, Multidisciplinary)

The energy spacing between the spin-doublet bound state of $$^4_{Lambda}$$He$$(1^+,0^+)$$ was determined to be $$1406 pm 2 pm 2$$ keV, by measuring $$gamma$$ rays for the $$1^+ to 0^+$$ transition with a high efficiency germanium detector array in coincidence with the $$^4{rm He}(K^-,pi^-)^4_{Lambda}$$He reaction at J-PARC. In comparison to the corresponding energy spacing in the mirror hypernucleus $$^4_{Lambda}$$H, the present result clearly indicates the existence of charge symmetry breaking (CSB) in $$Lambda N$$ interaction. By combining the energy spacings with the known ground-state binding energies, it is also found that the CSB effect is large in the $$0^+$$ ground state but is vanishingly small in the $$1^+$$ excited state, demonstrating that the $$Lambda N$$ CSB interaction has spin dependence.

論文

Double hypernuclei experiment with hybrid emulsion method at J-PARC

江川 弘行; J-PARC E07 Collaboration*

JPS Conference Proceedings (Internet), 8, p.021019_1 - 021019_6, 2015/09

ダブルハイパー核はストレンジネス$$S=$$-2の物理の研究において重要な要素である。これまでに核種が同定されたダブルハイパー核はKEK E373実験で観測された$${}^{6}_{LambdaLambda}$$Heのみである。J-PARC E07実験ではハイブリッドエマルジョン法を用いてダブルハイパー核の実験を行う。この実験では、K1.8ビームラインに設置されたKURAMAスペクトロメータシステムを用いて、$$(K^-,K^+)$$反応により生成された$$Xi^-$$を検出する。ターゲットの上流と下流に置かれたSSDによって$$Xi^-$$の軌跡を記録し、エマルジョン内の軌跡と自動的に結びつけることで、大量のダブルハイパー核を探索する。E373実験の10倍の統計が得られると見積もられており、10個以上の新しい核種を発見することを目指す。また、Ge検出器による$$Xi^-$$原子の$$X$$線測定も同時に行なう。この測定は世界初の試みであり、$$Xi^-$$の原子核表面付近でのポテンシャルの情報が得られる。この発表では、E07実験の現状と物理的意義について述べる。

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