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

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    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, eā€²K+) reaction at Jefferson Labā€™s 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 Ęp/pāŽ® \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 (āˆ’BĪ›, Ī“) = (0.25, 0.8)ā€‰MeV and (0.55, 4.7)ā€‰MeV, 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\u27Kāŗ) Reaction With a Tritium Target

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    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,eā€²K+) reaction, enhancements, which may correspond to a possible Ī›nn resonance and a pair of Ī£NN states, were observed with an energy resolution of about 1.21 MeV (Ļƒ), although greater statistics are needed to make definitive identifications. An experimentally measured Ī›nn state may provide a unique constraint in determining the Ī›n 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 (Kāˆ’,Ļ€āˆ’) 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 Ī›N\Lambda N Interaction: Gamma-Ray Spectroscopy of Ī›4^4_{\Lambda }He

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    The energy spacing between the ground-state spin doublet of Ī›4^4_\Lambda He(1+^+,0+^+) was determined to be 1406Ā±2Ā±21406 \pm 2 \pm 2 keV, by measuring Ī³\gamma rays for the 1+ā†’0+1^+ \to 0^+ transition with a high efficiency germanium detector array in coincidence with the 4^4He(Kāˆ’,Ļ€āˆ’)(K^-,\pi^-) Ī›4^4_\Lambda He reaction at J-PARC. In comparison to the corresponding energy spacing in the mirror hypernucleus Ī›4^4_\Lambda H, the present result clearly indicates the existence of charge symmetry breaking (CSB) in Ī›N\Lambda N interaction. It is also found that the CSB effect is large in the 0+0^+ ground state but is by one order of magnitude smaller in the 1+1^+ excited state, demonstrating that the Ī›N\Lambda N CSB interaction has spin dependence
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