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論文

Precise lifetime measurement of $$^4_Lambda$$H hypernucleus using in-flight $$^4$$He$$(K^-, pi^0)^4_Lambda$$H reaction

赤石 貴也; 橋本 直; 谷田 聖; 他35名*

Physics Letters B, 845, p.138128_1 - 138128_4, 2023/10

We present a new measurement of the $$^4_Lambda$$H hypernuclear lifetime using in-flight $$K^-$$ + $$^4$$He $$rightarrow$$ $$^4_Lambda$$H + $$pi^0$$ reaction at the J-PARC hadron facility. We demonstrate, for the first time, the effective selection of the hypernuclear bound state using only the $$gamma$$-ray energy decayed from $$pi^0$$. This opens the possibility for a systematic study of isospin partner hypernuclei through comparison with data from ($$K^-$$, $$pi^-$$) reaction. As the first application of this method, our result for the $$^4_Lambda$$H lifetime, $$tau(^4_Lambda mathrm{H}) = 206 pm 8 (mathrm{stat.}) pm 12 (mathrm{syst.}) mathrm{ps}$$, is one of the most precise measurements to date. We are also preparing to measure the lifetime of the hypertriton ($$^3_Lambda$$H) using the same setup in the near future.

論文

Chiral symmetry restoration at high matter density observed in pionic atoms

西 隆博*; 橋本 直; 他46名*

Nature Physics, 19(6), p.788 - 793, 2023/06

 被引用回数:2 パーセンタイル:83.24(Physics, Multidisciplinary)

According to quantum chromodynamics, vacuum is not an empty space, because it is filled with quark-antiquark pairs. The pair has the same quantum numbers as the vacuum and forms a condensate because the strong interaction of the quantum chromodynamics is too strong to leave the vacuum empty. This quark-antiquark condensation, the chiral condensate, breaks the chiral symmetry of the vacuum. The expectation value of the chiral condensate is an order parameter of the chiral symmetry, which is expected to decrease at high temperatures or high matter densities where the chiral symmetry is partially restored. Head-on collisions of nuclei at ultra-relativistic energies have explored the high-temperature regime, but experiments at high densities are rare. Here we measure the spectrum of pionic $$^{121}$$Sn atoms and study the interaction between the pion and the nucleus. We find that the expectation value of the chiral condensate is reduced at finite density compared to the value in vacuum. The reduction is linearly extrapolated to the nuclear saturation density and indicates that the chiral symmetry is partially restored due to the extremely high density of the nucleus.

論文

Proof-of-principle experiment for testing strong-field quantum electrodynamics with exotic atoms; High precision X-ray spectroscopy of muonic neon

奥村 拓馬*; 橋本 直; 他40名*

Physical Review Letters, 130(17), p.173001_1 - 173001_7, 2023/04

 被引用回数:1 パーセンタイル:83.24(Physics, Multidisciplinary)

To test bound-state quantum electrodynamics (BSQED) in the strong-field regime, we have performed high-precision X-ray spectroscopy of the 5$$g$$-4$$f$$ and 5$$f$$-4$$d$$ transitions (BSQED contribution of 2.4 eV and 5.2 eV, respectively) of muonic neon atoms in the low-pressure gas phase without bound electrons. Muonic atoms have been recently proposed as an alternative to few-electron high-Z ions for BSQED tests by focusing on circular Rydberg states where nuclear contributions are negligibly small. We determined the $$5g_{9/2}$$-$$4f_{7/2}$$ transition energy to be 6297.08 $$pm$$ 0.04 (stat.) $$pm$$ 0.13 (syst.) eV using superconducting transition-edge sensor microcalorimeters (5.2-5.5 eV FWHM resolution), which agrees well with the most advanced BSQED theoretical prediction of 6297.26 eV.

論文

High-sensitive XANES analysis at Ce L$$_{2}$$-edge for Ce in bauxites using transition-edge sensors; Implications for Ti-rich geological samples

Li, W.*; 山田 真也*; 橋本 直; 奥村 拓馬*; 早川 亮大*; 新田 清文*; 関澤 央輝*; 菅 大暉*; 宇留賀 朋哉*; 一戸 悠人*; et al.

Analytica Chimica Acta, 1240, p.340755_1 - 340755_9, 2023/02

 被引用回数:1 パーセンタイル:34.31(Chemistry, Analytical)

希土類元素は放射性元素であるアクチノイドのアナログ元素としてしばしば利用される。セリウム(Ce)は希土類元素の中でも+3価と+4価の両方をとり得る特別な元素である。環境試料中のCeの+3価と+4価の比を調べる手段としてX線吸収端近傍構造(XANES)が有力であったが、チタン濃度が高いと蛍光X線の干渉のために測定ができないという問題があった。本研究では、L$$_{3}$$吸収端だけでなくL$$_{2}$$吸収端を調べ、さらに新しい検出器であるtransition-edge sensor (TES)を利用することでこれまでは測定が難しかった試料も測定可能にした。この結果は様々な環境試料に応用可能である。

論文

Pole position of $$Lambda(1405)$$ measured in $$d(K^-,n)piSigma$$ reactions

相川 脩*; 橋本 直; 谷田 聖; 他73名*

Physics Letters B, 837, p.137637_1 - 137637_8, 2023/02

 被引用回数:0 パーセンタイル:0.02(Astronomy & Astrophysics)

We measured a set of $$pi^pmSigma^mp$$, $$pi^0Sigma^0$$, and $$pi^-Sigma^0$$ invariant mass spectra below and above the $$bar{K}N$$ mass threshold in $$K^-$$-induced reactions on deuteron. We deduced the $$S$$-wave$$bar{K}NrightarrowpiSigma$$ and $$bar{K}Nrightarrowbar{K}N$$ scattering amplitudes in the isospin 0 channel in the framework of a $$bar{K}N$$ and $$piSigma$$ coupled channel. We find that a resonance pole corresponding to $$Lambda(1405)$$ is located at 1417.7$$^{+6.0}_{-7.4}$$(fitting errors)$$^{+1.1}_{-1.0}$$(systematic errors) + $$[-26.1^{+6.0}_{-7.9}$$(fitting errors)$$^{+1.7}_{-2.0}$$(systematic errors)]$$i$$ MeV/$$c^2$$, closer to the $$bar{K}N$$ mass threshold than the value determined by the Particle Data Group.

論文

Measurements of strong-interaction effects in kaonic-helium isotopes at sub-eV precision with X-ray microcalorimeters

橋本 直; 谷田 聖; 他68名*

Physical Review Letters, 128(11), p.112503_1 - 112503_6, 2022/03

 被引用回数:4 パーセンタイル:79.93(Physics, Multidisciplinary)

We have measured the $$3d to 2p$$ transition X-rays of kaonic $$^3$$He and $$^4$$He atoms using superconducting transition-edge-sensor microcalorimeters with an energy resolution better than 6 eV (FWHM). We determined the energies to be $$6224.5 pm 0.4$$ (stat) $$pm 0.2$$ (syst) eV and $$6463.7pm 0.3$$ (stat) $$pm 0.1$$ (syst) eV, and widths to be $$2.5pm 1.0$$ (stat) $$pm 0.4$$ (syst) eV and $$1.0 pm 0.6$$ (stat) $$pm 0.3$$ (stat) eV, for kaonic $$^3$$He and $$^4$$He, respectively. These values are nearly 10 times more precise than in previous measurements. Our results exclude the large strong-interaction shifts and widths that are suggested by a coupled-channel approach, and agree with calculations based on optical-potential models.

論文

Dynamical response of transition-edge sensor microcalorimeters to a pulsed charged-particle beam

奥村 拓馬*; 東 俊行*; Bennet, D. A.*; Caradonna, P.*; Chiu, I.-H.*; Doriese, W. B.*; Durkin, M. S.*; Fowler, J. W.*; Gard, J. D.*; 橋本 直; et al.

IEEE Transactions on Applied Superconductivity, 31(5), p.2101704_1 - 2101704_4, 2021/08

 被引用回数:1 パーセンタイル:11.71(Engineering, Electrical & Electronic)

超伝導転移端センサー(TES)マイクロ熱量計は、優れたエネルギー分解能と高い効率を持った、加速器施設での実験に理想的なX線検出器である。高強度パルス荷電粒子ビームを用いたTES検出器の性能を研究するために、日本の陽子加速器研究施設(J-PARC)でパルスミュオンビームを用いてX線スペクトルを測定した。X線エネルギーの実質的な時間的シフトがパルスミュオンビームの到着時間と相関していることを発見した。これは、最初のパルスビームからのエネルギー粒子の入射によるパルスパイルアップによって合理的に説明された。

論文

Deexcitation dynamics of muonic atoms revealed by high-precision spectroscopy of electronic $$K$$ X rays

奥村 拓馬*; 東 俊行*; Bennet, D. A.*; Caradonna, P.*; Chiu, I. H.*; Doriese, W. B.*; Durkin, M. S.*; Fowler, J. W.*; Gard, J. D.*; 橋本 直; et al.

Physical Review Letters, 127(5), p.053001_1 - 053001_7, 2021/07

 被引用回数:9 パーセンタイル:78.48(Physics, Multidisciplinary)

超伝導遷移エッジ型センサーマイクロカロリメーターを用いて、鉄のミュー原子から放出される電子$$K$$X線を観測した。FWHMでの5.2eVのエネルギー分解能により、電子特性$$K$$$$alpha$$および$$K$$$$beta$$X線の非対称の広いプロファイルを約6keVの超衛星線$$K$$$$alpha$$線とともに観察することができた。このスペクトルは、電子のサイドフィードを伴う、負ミュオンと$$L$$殻電子による核電荷の時間依存スクリーニングを反映している。シミュレーションによると、このデータは電子$$K$$殻および$$L$$殻の正孔生成と、ミュオンカスケードプロセス中のそれらの時間発展を明確に示している。

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

 被引用回数:8 パーセンタイル:80.33(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

 被引用回数:28 パーセンタイル:95.73(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

Observation of a $$bar{K}NN$$ bound state in the $$^{3}$$He $$(K^-, Lambda p)n$$ reaction

山我 拓巳*; 橋本 直; 谷田 聖; 他66名*

Physical Review C, 102(4), p.044002_1 - 044002_14, 2020/10

 被引用回数:13 パーセンタイル:87.6(Physics, Nuclear)

We have performed an exclusive measurement of the $$K^{-}+! ~^{3}{rm He} to Lambda pn$$ reaction at an incident kaon momentum of $$1 {rm GeV}/c$$. In the $$Lambda p$$ invariant mass spectrum, a clear peak was observed below the mass threshold of $$bar{K}+N+N$$, as a signal of the kaonic nuclear bound state, $$bar{K}NN$$. The binding energy, decay width, and $$S$$-wave Gaussian reaction form-factor of this state were observed to be $$B_{K} = 42pm3({rm stat.})^{+3}_{-4}({rm syst.}) {rm MeV}$$, $$Gamma_{K} = 100pm7({rm stat.})^{+19}_{-9}({rm syst.}) {rm MeV}$$, and $$Q_{K} = 383pm11({rm stat.})^{+4}_{-1}({rm syst.}) {rm MeV}/c$$, respectively. The total production cross-section of $$bar{K}NN$$, determined by its $$Lambda p$$ decay mode, was $$sigma^{tot}_{K} cdot BR_{Lambda p} = 9.3pm0.8({rm stat.})^{+1.4}_{-1.0}({rm syst.}) mu{rm b}$$. We estimated the branching ratio of the $$bar{K}NN$$ state to the $$Lambda p$$ and $$Sigma^{0}p$$ decay modes as $$BR_{Lambda p}/BR_{Sigma ^{0}p} sim 1.7$$, by assuming that the physical processes leading to the $$Sigma N!N$$ final states are analogous to those of $$Lambda pn$$.

論文

$$K^-pp$$ bound system at J-PARC

佐久間 史典*; 橋本 直; 谷田 聖; 他66名*

AIP Conference Proceedings 2249, p.020005_1 - 020005_10, 2020/07

 被引用回数:1 パーセンタイル:69.41

The $$bar{K}NN$$ bound system, symbolically denoted as "$$K^-pp$$", is the simplest $$bar{K}$$-nuclear bound system which has been widely discussed as a consequence of the strongly attractive $$bar{K}N$$ interaction in $$I = 0$$ channels. Many theoretical works have pointed out the existence of the "$$K^-pp$$" bound system, but the calculated properties such as the binding energy and the width spread out due to the uncertainty of the $$bar{K}N$$ interaction below the $$bar{K}+N$$ mass threshold. Experimentally, there are several reports on observation of a "$$K^-pp$$" candidate with the binding energy of around 100 MeV, however, no definitive evidence was available so far. At J-PARC, we conducted a experimental search for the "$$K^-pp$$" bound system using $$K^- + ^3$$He reaction at 1.0 GeV/$$c$$ where the "$$K^-pp$$" is expected to be directly produced via the $$(K^-, n)$$ reaction. We finally observed a bound state below the $$K^- +p+p$$ mass threshold in the $$Lambda pn$$ final state, which can be interpreted as the "$$K^- pp$$" bound state. The possible existence of the "$$K^- pp$$" state is discussed from both aspects of production and decay.

論文

$$bar{K}$$-nuclear bound state at J-PARC

佐久間 史典*; 橋本 直; 谷田 聖; 他66名*

JPS Conference Proceedings (Internet), 32, p.010088_1 - 010088_8, 2020/07

$$bar{K}$$-nuclear bound states have been widely discussed as a consequence of the strongly attractive $$bar{K}N$$ interaction in $$I = 0$$ channels. Especially, the simplest $$bar{K}$$-nuclear bound state of $$bar{K}NN$$ (denoted as "$$K^-pp$$") has attracted the strong interest both of theoretical and experimental studies. We observed a bound state below the $$K^- + p + p$$ mass threshold with in-flight $$K^-$$ induced reactions on $$^3$$He target, which can be interpreted as the "$$K^-pp$$" bound state. The possible existence of the "$$K^-pp$$" state is discussed from both aspects of production and decay: "$$K^-pp$$" and $$Lambda(1405)p$$ productions, and non-mesonic $$Lambda p$$ and mesonic $$(pi Sigma)^0p$$ decays, respectively.

論文

Results of $$bar{K}NN$$ search via the $$(K^-, n)$$ reaction at J-PARC

山我 拓巳*; 橋本 直; 谷田 聖; 他66名*

JPS Conference Proceedings (Internet), 26, p.023008_1 - 023008_6, 2019/11

There is a long-standing argument of the existence of kaonic nucleus, which is a bound state of anti-kaon and nucleus. Theoretically, its existence is strongly supported, however its binding energy and width have not been established yet. It is strongly desired to have an experiment to investigate the simplest kaonic nucleus, so-called $$K^-pp$$ bound state. We performed an experiment to search for $$K^-pp$$ via the in-flight $$(K^-, n)$$ reaction at J-PARC. By studying $$Lambda p$$ invariant mass spectrum in the $$Lambda pn$$ final state and its dependence on momentum transfer of $$K^{-}N to bar{K}N$$, we observed a resonant state located below $$M_{K^{-}pp}$$. The mass and width of this resonant state are $$2324 pm 3(textit{stat}.)_{-3}^{+6}(textit{syst}.)$$ MeV/$$c^2$$, and $$115 pm 7(textit{stat}.)_{-20}^{+10}(textit{syst}.)$$ MeV, respectively, which can be naturally interpreted as a theoretically predicted $$K^-pp$$ bound state.

論文

$$Lambda(1405)$$ spectroscopy via the in-flight $$d(K^-, n)$$ reaction at the J-PARC K1.8BR

川崎 新吾*; 橋本 直; 谷田 聖; 他72名*

JPS Conference Proceedings (Internet), 26, p.022009_1 - 022009_5, 2019/11

The spectral shape of the $$Lambda(1405)$$ baryon was measured via the in-flight $$d(K^-, n)$$ reaction at the J-PARC K1.8BR beam-line (J-PARC E31). The second E31 physics run was carried out in January and February, 2018. Approximately $$3.9 times 10^{10}$$ kaons were irradiated on the deuteron target. The missing mass spectrum for the $$d(K^-, n)$$ where the residual final-state particles were $$Sigma^0$$ and $$pi^0$$ ($$d(K^-, n)$$"$$Sigma^0pi^0$$" spectrum) was measured for the first time.

論文

Spectroscopic study of the $$Lambda$$(1405) resonance via the $$d(K^-, n)$$ reaction at J-PARC

浅野 秀光*; 橋本 直; 谷田 聖; 他72名*

AIP Conference Proceedings 2130, p.040018_1 - 040018_6, 2019/07

 被引用回数:3 パーセンタイル:82.57

The structure of the $$Lambda(1405)$$ hyperon is an important and long-standing issue related to the $$bar{K}$$-nucleus interaction. The J-PARC E31 experiment has been performed to investigate the $$Lambda(1405)$$ spectrum shape. Because it is hard to form the $$Lambda(1405)$$ directly by a $$bar{K}N$$ scattering in free space, E31 uses the $$d(K^-, n)$$ reaction with an incident kaon momentum of 1 GeV/$$c$$. We will identify three final states - $$Sigma^-pi^+$$, $$Sigma^+pi^-$$, $$Sigma^0pi^0$$ so that the isospin structure of hyperon resonance states produced can be decomposed. The first physics run of the E31 experiment was performed in 2016. To enhance the statistics of the data set, we have performed the second physics run in the beginning of 2018. During the second run of E31, around $$3.9 times 10^{10}$$ kaons impacted on the deuteron target.

論文

"$$K^-pp$$", a $$bar K$$-meson nuclear bound state, observed in $$^3$$He($$K^-,Lambda p)n$$ reactions

橋本 直; 谷田 聖; 他67名*

Physics Letters B, 789, p.620 - 625, 2019/02

 被引用回数:32 パーセンタイル:95.3(Astronomy & Astrophysics)

$$^{3}{rm He}(K^-, , Lambda p)n$$における$$Lambda p$$不変質量分布において$$m_K + 2m_p$$、つまり$$K^-$$が2つの陽子に束縛する質量閾値以下に顕著なピークを観測した。$$q$$ = 350$$sim$$650MeV/$$c$$という比較的大きな運動量移行領域を選ぶことで、準弾性散乱($$overline{K}N rightarrow overline{K}N$$)に続いて残りの2各紙に吸収される反応($$overline{K}NN rightarrow Lambda N$$)をはっきり分離することができる。観測したピークの単純なフィットによってBreit-Wignerポール位置$$B_{rm {it Kpp}} = 47 pm 3 , (stat.) ,^{+3}_{-6},(sys.)$$ MeV、幅$$Gamma_{rm {it Kpp}} = 115 pm 7 , (stat.),^{+10}_{-20} ,(sys.)$$ MeV、そして$$S$$波ガウス形状因子パラメータ$$Q_{rm {it Kpp}} = 381 pm 14 , (stat.),^{+57}_{-0} ,(sys.)$$MeV/$$c$$という値が"$$K^-pp$$"というストレンジネスを含む新しい原子核束縛システムについて得られた。

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

 被引用回数:23 パーセンタイル:84.13(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

Kaonic-atom X-ray spectroscopy with superconducting microcalorimeters

橋本 直; 谷田 聖; 他45名*

JPS Conference Proceedings (Internet), 17, p.072001_1 - 072001_4, 2017/07

We will measure kaonic helium X-rays using transition-edge-sensor microcalorimeters, TES, in the J-PARC hadron experimental facility. To demonstrate the feasibility of the experiment, we performed a measurement of pionic carbon X-rays at PSI, where an excellent FWHM energy resolution of 7 eV at 6.4 keV was achieved. We also evaluated the expected TES performance in the kaon beam at J-PARC. The simulation results show that the TES spectrometer would work with a good energy resolution, and clear peaks of kaonic helium X-rays would be observed on a reasonably suppressed background.

論文

Spectroscopic study of hyperon resonance below $$bar{K}N$$ threshold via the $$d(K^-,n)$$ reaction

井上 謙太郎*; 橋本 直; 谷田 聖; 他69名*

JPS Conference Proceedings (Internet), 17, p.072003_1 - 072003_4, 2017/07

We have taken the data of the $$(K^-,n)$$ reaction on the $$D_2$$ target in May, 2015. In this reaction, it is expected that the $$K^-$$ kicks a neutron and produces the $$Lambda(1405)$$ in a backward angle. We identify the final state of $$K^- d to npi^+pi^-n$$ by detecting the forward neutron, $$pi^+$$ and $$pi^-$$ and obtain the $$d(K^-,n)pi^{mp}Sigma^{pm}$$ spectrum excluded $$K^0$$ and forward-going $$Sigma$$ productions. We observed few hundred events in the region below the $$bar{K}N$$ threshold.

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