95 research outputs found
The Cross-Section Measurement for the \u3csup\u3e3\u3c/sup\u3eH (e, e\u27, K\u3csup\u3e+\u3c/sup\u3e) nnĪ Reaction
The small binding energy of the hypertriton leads to predictions of the non-existence of bound hypernuclei for isotriplet three-body systems such as nnĪ. However, invariant mass spectroscopy at GSI has reported events that may be interpreted as the bound nnĪ state. The nnĪ state was sought by missing-mass spectroscopy via the (e, eā²K+) reaction at Jefferson Labās experimental Hall A. The present experiment has higher sensitivity to the nnĪ-state investigation in terms of better precision by a factor of about three. The analysis shown in this article focuses on the derivation of the reaction cross-section for the 3H(Ī³*, K+)X reaction. Events that were detected in an acceptance, where a Monte Carlo simulation could reproduce the data well (ā Ęp/pā® \u3c 4%), were analyzed to minimize the systematic uncertainty. No significant structures were observed with the acceptance cuts, and the upper limits of the production cross-section of the nnĪ state were obtained to be 21 and 31nbsr-1 at the 90% confidence level when theoretical predictions of (āBĪ, Ī) = (0.25, 0.8)āMeV and (0.55, 4.7)āMeV, respectively, were assumed. The cross-section result provides valuable information for examining the existence of nnĪ
Spectroscopic Study of a Possible Ī Resonance and a Pair of (e, e\u27Kāŗ) Reaction With a Tritium Target
A mass spectroscopy experiment with a pair of nearly identical high-resolution spectrometers and a tritium target was performed in Hall A at Jefferson Lab. Utilizing the (e,eā²K+) reaction, enhancements, which may correspond to a possible Īnn resonance and a pair of Ī£NN states, were observed with an energy resolution of about 1.21 MeV (Ļ), although greater statistics are needed to make definitive identifications. An experimentally measured Īnn state may provide a unique constraint in determining the Īn interaction, for which no scattering data exist. In addition, although bound A = 3 and 4 Ī£ hypernuclei have been predicted, only an A=4 Ī£ hypernucleus (4Ī£He) was found, utilizing the (Kā,Ļā) reaction on a 4He target. The possible bound Ī£NN state is likely a Ī£ā°nn state, although this has to be confirmed by future experiments
Observation of Spin-Dependent Charge Symmetry Breaking in Interaction: Gamma-Ray Spectroscopy of He
The energy spacing between the ground-state spin doublet of He(1,0) was determined to be keV, by measuring
rays for the transition with a high efficiency germanium
detector array in coincidence with the He He
reaction at J-PARC. In comparison to the corresponding energy spacing in the
mirror hypernucleus H, the present result clearly indicates the
existence of charge symmetry breaking (CSB) in interaction. It is
also found that the CSB effect is large in the ground state but is by one
order of magnitude smaller in the excited state, demonstrating that the
CSB interaction has spin dependence
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