S.H. Hwang

Observation of Spin-Dependent Charge Symmetry Breaking in

The energy spacing between the spin-doublet bound state of _{Λ}^{4}He(1^{+},0^{+}) was determined to be 1406±2±2u2009u2009keV, by measuring γ rays for the 1^{+}→0^{+} transition with a high efficiency germanium detector array in coincidence with the ^{4}He(K^{-},π^{-})_{Λ}^{4}He reaction at J-PARC. In comparison to the corresponding energy spacing in the mirror hypernucleus _{Λ}^{4}H, the present result clearly indicates the existence of charge symmetry breaking (CSB) in ΛN 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 ΛN CSB interaction has spin dependence.

\Lambda N

A search forKpp bound state (the lightest kaonic nucleus) has been performe d using theγd → KπX reaction at Eγ=1.5-2.4 GeV at LEPS / Pring-8. The di fferential cross section of Kπ photo-production o ff deuterium has been measured for the first time in this energy region, and a bump st ructure was searched for in the inclusive missing mass spectrum. A statistically significant bump structure was no t observed in the region from 2.22 to 2.36 GeV /c2, and the upper limits of the di fferential cross section for the Kpp bound state production were determined to be 0.1 − 7μ b (95% confidence level) for a set of assumed binding energy and width values.

Interaction: Gamma-Ray Spectroscopy of

We have carried out an experiment to search for a neutron-ric h hypernucleus, 6 Λ H, by the6Li(π−,K+) reaction atpπ− =1.2 GeV/c. The obtained missing-mass spectrum with an estimated energy re solution of 3.2 MeV (FWHM) showed no peak structure correspo nding to the6 Λ H hypernucleus neither below nor above the 4 Λ H+2n particle decay threshold. An upper limit of the production c ross section for the bound6 Λ H hypernucleus was estimated to be 1.2 nb /sr at 90% confidence level.

^4_{\Lambda }

A search forKpp bound state (the lightest kaonic nucleus) has been performe d using theγd → KπX reaction at Eγ=1.5-2.4 GeV at LEPS / Pring-8. The di fferential cross section of Kπ photo-production o ff deuterium has been measured for the first time in this energy region, and a bump st ructure was searched for in the inclusive missing mass spectrum. A statistically significant bump structure was no t observed in the region from 2.22 to 2.36 GeV /c2, and the upper limits of the di fferential cross section for the Kpp bound state production were determined to be 0.1 − 7μ b (95% confidence level) for a set of assumed binding energy and width values.

He

We searched for the bound state of the neutron-rich Lambda-hypernucleus H-6(Lambda), using the Li-6(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 x 10(12) pi(-) was driven onto a Li-6 target of 3.5-g/cm(2) thickness. No event was observed below the bound threshold, i.e., the mass of H-4(Lambda) + 2n, in the missing-mass spectrum of the Li-6(pi(-), K+) X reaction in the 2 degrees < theta(pi K) < 20 degrees angular range. Furthermore, no event was found up to 2.8 MeV/c(2) above the bound threshold. We obtained the double-differential cross section spectra of the Li-6(pi(-), K+)X reaction in the angular range of 2 degrees < theta(pi K) < 14 degrees. An upper limit of 0.56 nb/sr (90% C.L.) was obtained for the production cross section of the H-6(Lambda) hypernucleus bound state. In addition, not only the bound state region, but also the Lambda continuum region and part of the Sigma(-) quasifree production region of the Li-6(pi(-), K+) reaction were obtained with high statistics. The present missing-mass spectrum will facilitate the investigation of the Sigma(-) -nucleus optical potential for Sigma(-) -He-5 through spectrum shape analysis.

Search for

We searched for the bound state of the neutron-rich Lambda-hypernucleus H-6(Lambda), using the Li-6(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 x 10(12) pi(-) was driven onto a Li-6 target of 3.5-g/cm(2) thickness. No event was observed below the bound threshold, i.e., the mass of H-4(Lambda) + 2n, in the missing-mass spectrum of the Li-6(pi(-), K+) X reaction in the 2 degrees < theta(pi K) < 20 degrees angular range. Furthermore, no event was found up to 2.8 MeV/c(2) above the bound threshold. We obtained the double-differential cross section spectra of the Li-6(pi(-), K+)X reaction in the angular range of 2 degrees < theta(pi K) < 14 degrees. An upper limit of 0.56 nb/sr (90% C.L.) was obtained for the production cross section of the H-6(Lambda) hypernucleus bound state. In addition, not only the bound state region, but also the Lambda continuum region and part of the Sigma(-) quasifree production region of the Li-6(pi(-), K+) reaction were obtained with high statistics. The present missing-mass spectrum will facilitate the investigation of the Sigma(-) -nucleus optical potential for Sigma(-) -He-5 through spectrum shape analysis.

K^-pp

We have carried out an experiment to search for a neutron-ric h hypernucleus, 6 Λ H, by the6Li(π−,K+) reaction atpπ− =1.2 GeV/c. The obtained missing-mass spectrum with an estimated energy re solution of 3.2 MeV (FWHM) showed no peak structure correspo nding to the6 Λ H hypernucleus neither below nor above the 4 Λ H+2n particle decay threshold. An upper limit of the production c ross section for the bound6 Λ H hypernucleus was estimated to be 1.2 nb /sr at 90% confidence level.

bound state via

We have carried out an experiment to search for a neutron-ric h hypernucleus, 6 Λ H, by the6Li(π−,K+) reaction atpπ− =1.2 GeV/c. The obtained missing-mass spectrum with an estimated energy re solution of 3.2 MeV (FWHM) showed no peak structure correspo nding to the6 Λ H hypernucleus neither below nor above the 4 Λ H+2n particle decay threshold. An upper limit of the production c ross section for the bound6 Λ H hypernucleus was estimated to be 1.2 nb /sr at 90% confidence level.

\gamma d \rightarrow K^+ \pi^-X

A search forKpp bound state (the lightest kaonic nucleus) has been performe d using theγd → KπX reaction at Eγ=1.5-2.4 GeV at LEPS / Pring-8. The di fferential cross section of Kπ photo-production o ff deuterium has been measured for the first time in this energy region, and a bump st ructure was searched for in the inclusive missing mass spectrum. A statistically significant bump structure was no t observed in the region from 2.22 to 2.36 GeV /c2, and the upper limits of the di fferential cross section for the Kpp bound state production were determined to be 0.1 − 7μ b (95% confidence level) for a set of assumed binding energy and width values.

reaction at

We have carried out an experiment to search for a neutron-ric h hypernucleus, 6 Λ H, by the6Li(π−,K+) reaction atpπ− =1.2 GeV/c. The obtained missing-mass spectrum with an estimated energy re solution of 3.2 MeV (FWHM) showed no peak structure correspo nding to the6 Λ H hypernucleus neither below nor above the 4 Λ H+2n particle decay threshold. An upper limit of the production c ross section for the bound6 Λ H hypernucleus was estimated to be 1.2 nb /sr at 90% confidence level.