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تسجيل مستخدم جديدSearch for the neutron-rich hypernucleus 9{Lambda}He
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Search for the neutron-rich hypernucleus 9LHe is reported by the FINUDA experiment at DAFNE, INFN-LNF, studying (pi+, pi-) pairs in coincidence from the K-stop + 9Be --> 9LHe + pi+ production reaction followed by 9LHe --> 9Li + pi- weak decay. An upper limit of the production rate of 9LHe undergoing this two-body pi- decay is determined to be (2.3 +/- 1.9) 10-6/K-stop at 90% confidence level.
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The missing mass spectroscopy of the $^{7}_{Lambda}$He hypernucleus was performed, using the $^{7}$Li$(e,e^{prime}K^{+})^{7}_{Lambda}$He reaction at the Thomas Jefferson National Accelerator Facility Hall C. The $Lambda$ binding energy of the ground
state (1/2$^{+}$) was determined with a smaller error than that of the previous measurement, being $B_{Lambda}$ = 5.55 $pm$ 0.10(stat.) $pm$ 0.11(sys.) MeV. The experiment also provided new insight into charge symmetry breaking in p-shell hypernuclear systems. Finally, a peak at $B_{Lambda}$ = 3.65 $pm$ 0.20(stat.) $pm$ 0.11(sys.) MeV was observed and assigned as a mixture of 3/2$^{+}$ and 5/2$^{+}$ states, confirming the gluelike behavior of $Lambda$, which makes an unstable state in $^{6}$He stable against neutron emission.
The 8He(d,p) reaction was studied in inverse kinematics at 15.4A MeV using the MUST2 Si-CsI array in order to shed light on the level structure of 9He. The well known 16O(d,p)17O reaction, performed here in reverse kinematics, was used as a test to v
alidate the experimental methods. The 9He missing mass spectrum was deduced from the kinetic energies and emission angles of the recoiling protons. Several structures were observed above the neutron-emission threshold and the angular distributions were used to deduce the multipolarity of the transitions. This work confirms that the ground state of 9He is located very close to the neutron threshold of 8He and supports the occurrence of parity inversion in 9He.
We performed a coincidence measurement of two nucleons emitted from the nonmesonic weak decay (NMWD) of ^{5}_{Lambda}He formed via the ^{6}Li(pi^+,K^+) reaction. The energies of two nucleons and the pair number distributions in the opening angle betw
een them were measured. In both np and nn pairs, we observed a clean back-to-back correlation coming from the two-body decay of Lambda p --> n p and Lambda n --> n n, respectively. The ratio of the nucleon pair numbers was N_{nn}/N_{np}=0.45 pm 0.11(stat)pm 0.03(syst) in the kinematic region of cos(theta_{NN}) < -0.8. Since each decay mode was exclusively detected, the measured ratio should be close to the ratio of Gamma(Lambda p --> np)/Gamma(Lambda n --> nn). The ratio is consistent with recent theoretical calculations based on the heavy meson/direct quark exchange picture.
An experiment with a newly developed high-resolution kaon spectrometer (HKS) and a scattered electron spectrometer with a novel configuration was performed in Hall C at Jefferson Lab (JLab). The ground state of a neutron-rich hypernucleus, He 7 Lambd
a, was observed for the first time with the (e,eK+) reaction with an energy resolution of ~0.6 MeV. This resolution is the best reported to date for hypernuclear reaction spectroscopy. The he 7 Lambda binding energy supplies the last missing information of the A=7, T=1 hypernuclear iso-triplet, providing a new input for the charge symmetry breaking (CSB) effect of Lambda N potential.
The neutron rich nucleus $^{193}$Os was produced in the $^{192}$Os($^{7}$Li,$^{6}$Li)$^{193}$Os reaction. An isomeric state based on the $9/2^-$[505] nilsson orbital was identified in the present work. Half-life of the isomeric state was extracted an
d discussed in terms of the $K$ quantum number. Level scheme built on the isomeric state was proposed based on the experimental data.
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