K. Hosomi, a Y. Ma, b S. Ajimura, c K. Aoki, S. Dairaku, Y. Y. Fu, H. Fujioka, d K. Futatsukawa, e W. Imoto, Y. Kakiguchi, M. Kawai, S. Kinoshita, T. Koike, N. Maruyama, M. Mimori, S. Minami, f Y. Miura, K. Miwa, g Y. Miyagi, T. Nagae, d D. Nakajima, h H. Noumi, c K. Shirotori, c T. Suzuki, c T. Takahashi, T. N. Takahashi, c H. Tamura, K. Tanida, i N. Terada, A. Toyoda, K. Tsukada, j M. Ukai, g and S. H. Zhou

The level structure of the |${}^{12}_{\Lambda }{\rm C}$| hypernucleus was precisely determined by means of |$\gamma$|-ray spectroscopy. We identified four |$\gamma$|-ray transitions via the |${}^{12}{\rm C}(\pi ^{+ },K^{+ }\gamma )$| reaction using a germanium detector array, Hyperball2. The spacing of the ground-state doublet |$(2^{-},1^{-}_{1})$| was measured to be |$161.5 \pm 0.3{\text {(stat)}}\pm 0.3(\hbox {syst})$|keV from the direct |$M1$| transition. Excitation energies of the |$1^{-}_{2}$| and |$1^{-}_{3}$| states were measured to be |$2832\pm 3\pm 4$|keV and |$6050\pm 8\pm 7$|keV, respectively. The level energies obtained provide definitive references for the reaction spectroscopy of |$\Lambda$| hypernuclei.

The level structure of the C-12(Lambda) hypernucleus was precisely determined by means of gamma-ray spectroscopy. We identified four gamma-ray transitions via the C-12(pi(+), K+gamma) reaction using a germanium detector array, Hyperball2. The spacing of the ground-state doublet (2(-) , 1(1)(-))was measured to be 161.5 +/- 0.3(stat) +/- 0.3(syst) keV from the direct M1 transition. Excitation energies of the 1(2)(-) and 1(3)(-) states were measured to be 2832 +/- 3 +/- 4 keV and 6050 +/- 8 +/- 7 keV, respectively. The level energies obtained provide definitive references for the reaction spectroscopy of Lambda hypernuclei.

A γ-ray spectroscopy experiment via the C12(π+,K+) reaction was carried out at KEK-PS in 2005. The K6 beam line and Superconducting Kaon Spectrometer (SKS) were employed to obtain a missing mass spectrum for 12ΛC. An upgraded germanium detector array, Hyperball2, was introduced to detect γ rays emitted from hypernuclei in coincidence with the (π+,K+) reaction. As a result of further analysis, a γ-ray peak at 6048 keV (preliminary) was newly observed and assigned as the M1 transition from the 6-MeV excited state to the ground state.

Since 1998 we have conducted the project of precision hypernuclear γ-ray spectroscopy using the Ge detector array, Hyperball, and revealed precise level schemes of various p-shell hypernuclei. In the latest experiment at KEK (E566), the ground-state spacing of CΛ11 and CΛ12 hypernuclei have been obtained using the C12(π+,K+)BΛ11,CΛ12 reaction. The accumulated data on the p-shell hypernuclear level energies allow us to establish all of the four strengths of the ΛN spin-dependent interactions and to discuss the ΛN-ΣN coupling force in a nucleus. Further experiments at J-PARC are being prepared, where we tackle new experimental challenges such as a precise measurement of the Λ-spin-flip B(M1) values and exploration of sd-shell hypernuclei.

The updated results from the hypernuclear γ-ray spectroscopy experiment, KEK-E566, are presented in this paper with emphasis on the γ-ray spin assignment. The KEK-E566 experiment was performed at the KEK-PS K6 beam line in 2005. In this experiment, C12(π+,K+)CΛ12 reaction was used to produce CΛ12/BΛ11 hypernuclei. A germanium detector array, Hyperball2, was constructed to detect γ rays emitted from the hypernuclei. Six hypernuclear γ-ray peaks were observed and assigned successfully.

In this proceeding,we will first outline the experimental setup and main results of the most recent hypernuclear γ-ray spectroscopy experiment （KEK-E566） performed at KEK-PS K6 beam line. The main feature and characteristics of this type of research will be emphasised. After that,the approved experimental proposal （E13） at J-PARC facility will be introduced briefly.

A series of hypernuclear γ-ray spectroscopy experiments using a germanium detector array, Hyperball, have accumulated precise data on various p-shell Λ hypernuclei. Recently, 12ΛC and 11ΛB were studied at KEK using the (π+,K+γ) reaction, and a transition from a directly-populated spin-flip state, 16ΛO(2−), was observed in BNL E930 data. It is discussed whether the spin-dependent ΛN interaction parameters determined from previous experiments can consistently explain other γ spectroscopy data. At the J-PARC facility, further hypernuclear γ-ray spectroscopy experiments are planned, particularly to measure the g factor of a Λ in a nucleus from a spin-flip B(M1) value and to investigate the ΛN interaction more in detail.

Hypernuclear γ-ray spectroscopy experiments using a germanium detector array, Hyperball, have accumulated precise data on various p-shell Λ hypernuclei. A common parameter set of the spin-dependent effective interaction strengths (Δ, SΛ, SN, and T), which reproduces most of the hypernuclear data, has been determined. In the J-PARC facility, further experiments of hypernuclear γ-ray spectroscopy are planned to be performed.

The total cross sections for the π+π− photoproduction on the deuteron were measured in an energy range of 0.8 to 1.1 GeV. The obtained total cross section for the quasi-free π+π− photoproduction on the deuteron was about 60 % of those on the free proton. The cross section for Δ++Δ− photoproduction was derived from the non-quasi-free π+π− photoproduction events. It was smaller than the previous data.

We present our plan to measure X rays from Ξ − atoms for the first time in the world at J-PARC. The measurement of X rays from Ξ − atoms is a promising method to study the optical potential between Ξ − and a nucleus as proved in the cases of other negative hadrons (π −, K −, \( \bar p \) , and Σ −). While we are intending to measure X rays from as many targets as possible over the periodic table, we have chosen Fe (iron) as the first target because the measurement will be the easiest and because large X-ray energy shift and width may be expected. Choice of other targets will be determined based on the result of the first experiment. We can accumulate several thousand counts of X rays and determine its energy shift down to ∼0.05 keV. This is sensitive enough to observe expected energy shift (∼1 keV) with reasonable accuracy, while sensitivities for X-ray width is somewhat weaker (measurable down to ∼1 keV).

From the 12C(π +, K +) 12 ΛC reaction, the γ-rays of 261.60.24keV (7/2 +5/2 +) and 1481.70.7keV (1/2 +5/2 +) of 11 ΛB, and 2667.32.8keV (1 2 -2 1 -) of 12 ΛC hypernuclei have been identified using a large germanium detector array Hyperball2 at K6 beam line of KEK. The observed energies of the transitions 1481.7keV and 261.6keV are significantly different from the values predicted by the shell model using the Δ and S N parameters determined from the 7 ΛLi data. © 2007 Chinese Physical Society and IOP Publishing Ltd.

In this paper, a preliminary result from the latest hypernuclear γ -ray spectroscopy experiment (KEK-E566) is presented together with a short discussion. The experiment was performed at the KEK-PS K6 beam line in 2005. In this experiment, the 12C(π+, K +)12 ΛC reaction was employed to populate 12 ΛC/11 ΛB hypernuclei. A germanium detector array, Hyperball2, was constructed to detect γ -rays emitted from the hypernuclei produced. Three hypernuclear γ -ray peaks were observed and assigned.

<正>本工作涉及的1Λ2C和1Λ1B超核的γ谱学实验的目的是在交叉检验前实验确定与自旋相关的ΛN相互作用参数。试图通过测量1Λ2C基态二重态能级间隔来理解1Λ0B基态二重态能量间隔的理论预期值与

In this paper, a preliminary result from the latest bypernuclear gamma-ray spectroscopy experiment (KEK-E566) is presented together with a short discussion. The experiment was performed at the KEK-PS K6 beam line in 2005. In this experiment, the C-12(pi(+), K+)(Lambda)C-12 reaction was employed to populate C-12(Lambda)/B-11(Lambda) hypernuclei. A germanium detector array, Hyperball2, was constructed to detect gamma-rays emitted from the hypernuclei produced. Three hypernuclear gamma-ray peaks were observed and assigned.

From the 12C(π+, K+)12ΛC reaction, the γ-rays of 261.6±0.24 keV (7/2+→5/2+) and 1481.7±0.7 keV (1/2+→5/2+) of 11ΛB, and 2667.3±2.8 keV (12−→21−) of 12ΛC hypernuclei have been identified using a large germanium detector array Hyperball2 at K6 beam line of KEK. The observed energies of the transitions 1481.7 keV and 261.6 keV are significantly different from the values predicted by the shell model using the Δ and SN parameters determined from the 7ΛLi data.