High Resolution Spectroscopy of 12B_Lambda by Electroproduction

An experiment measuring electroproduction of hypernuclei has been performed in Hall A at Jefferson Lab on a $^{12}$C target. In order to increase counting rates and provide unambiguous kaon identification two superconducting septum magnets and a Ring Imaging CHerenkov detector (RICH) were added to the Hall A standard equipment. An unprecedented energy resolution of less than 700 keV FWHM has been achieved. Thus, the observed \lam{12}{B} spectrum shows for the first time identifiable strength in the core-excited region between the ground-state {\it s}-wave $\Lambda$ peak and the 11 MeV {\it p}-wave $\Lambda$ peak.Comment: Paper submitted to Physical Review Letter

Spectroscopy of Lambda-9Li by electroproduction

In the absence of accurate data on the free two-body hyperon-nucleon interaction, the spectra of hypernuclei can provide information on the details of the effective hyperon-nucleon interaction. Electroproduction of the hypernucleus Lambda-9Li has been studied for the first time with sub-MeV energy resolution in Hall A at Jefferson Lab on a 9Be target. In order to increase the counting rate and to provide unambiguous kaon identification, two superconducting septum magnets and a Ring Imaging CHerenkov detector (RICH) were added to the Hall A standard equipment. The cross section to low-lying states of Lambda-9Li is concentrated within 3 MeV of the ground state and can be fitted with four peaks. The positions of the doublets agree with theory while a disagreement could exist with respect to the relative strengths of the peaks in the doublets. A Lambda separation energy of 8.36 +- 0.08 (stat.) +- 0.08 (syst.) MeV was measured, in agreement with an earlier experiment.Comment: 14 pages, 8 figure

High-Resolution Spectroscopy of N-16(Lambda) [ superscript 16 subscript lambda N] by Electroproduction

An experimental study of the 16O(e,e′K+)Λ16N [superscript 16 O (e, e prime K superscript +) superscript 16 subscript lambda N] reaction has been performed at Jefferson Lab. A thin film of falling water was used as a target. This permitted a simultaneous measurement of the p(e,e′K+)Λ,Σ0 [p (e, e prime K superscript +) lambda, sigma superscript 0] exclusive reactions and a precise calibration of the energy scale. A ground-state binding energy of 13.76±0.16  MeV was obtained for Λ16N [superscript 16 subscript lambda N] with better precision than previous measurements on the mirror hypernucleus Λ16O [superscript 16 subscript lambda O]. Precise energies have been determined for peaks arising from a Λ [lambda]in s and p orbits coupled to the p1/2 [p subscript 1/2] and p3/2 [p subscript 3/2] hole states of the 15N [superscript 15 N] core nucleusUnited States. Dept. of Energy (Contract No. DE-AC05-84ER40150)Czech Science Foundation (Grant no. 202/08/ 0984)United States. Dept. of Energy (Contract No. DE-AC02-06CH11357)United States. Dept. of Energy (Contract No. DE-FG02-99ER41110)United States. Dept. of Energy (Contract No. DE-AC02-98-CH10886)National Science Foundation (U.S.

High-resolution hypernuclear spectroscopy at Jefferson Lab, Hall A

International audienceThe experiment E94-107 in Hall A at Jefferson Lab started a systematic study of high-resolution hypernuclear spectroscopy in the 0p-shell region of nuclei such as the hypernuclei produced in electroproduction on Be9,C12, and O16 targets. In order to increase counting rates and provide unambiguous kaon identification, two superconducting septum magnets and a ring-imaging Cherenkov detector were added to the Hall A standard equipment. The high-quality beam, the good spectrometers, and the new experimental devices allowed us to obtain very good results. For the first time, measurable strength with sub-MeV energy resolution was observed for the core-excited states of BΛ12. A high-quality NΛ16 hypernuclear spectrum was likewise obtained. A first measurement of the Λ binding energy for NΛ16, calibrated against the elementary reaction on hydrogen, was obtained with high precision, 13.76±0.16 MeV. Similarly, the first LiΛ9 hypernuclear spectrum shows general agreement with theory (distorted-wave impulse approximation with the SLA and BS3 electroproduction models and shell-model wave functions). Some disagreement exists with respect to the relative strength of the states making up the first multiplet. A Λ separation energy of 8.36 MeV was obtained, in agreement with previous results. It has been shown that the electroproduction of hypernuclei can provide information complementary to that obtained with hadronic probes and the γ-ray spectroscopy technique