Spectroscopic study of the Lambda hypernuclei by the (e,e'K+) reaction
- Tohoku Univ., Sendai (Japan)
Hypernuclear spectroscopy study via the (e,e'K+) reaction has been carried out for the first time, establishing a new technique to study Lambda hypernuclei. The high quality electron beam at Jefferson Lab made it possible to measure Lambda hypernuclear spectra with an energy resolution better than 1 MeV (FWHM). The present experiment was designed to make full use of the virtual photon flux, which peaks at very forward angles, by detecting scattered electrons at 0 degrees. Scattered positive kaons were also detected near 0 degrees, where the cross section of the kaon photo-production is maximized. This unique kinematical configuration was realized with the HyperNuclear Spectrometer System (HNSS), which consisted of the Short-Orbit Spectrometer, the Enge Split-Pole Spectrometer, and the splitter magnet. The $$12\atop{Λ}$$B mass spectrum was measured in the 12C(e,e'K+)$$12\atop{Λ}$$ reaction with 0.9 MeV (FWHM) energy resolution. The averaged binding energy of the $$12\atop{Λ}$$B ground state doublet was obtained to be 11.7 ± 0.1 (statistical) ± 0.3 (systematic) MeV, which is consistent with emulsion data. The general spectral structure of the 12C(e,e'K+) $$12\atop{Λ}$$B reaction was found to be similar to that of the 12C(Λ+,K+)$$12\atop{Λ}$$C reaction, showing characteristic peaks corresponding to sLambda and pLambda orbits, as well as a few core-excited states. The cross section of the $$12\atop{Λ}$$B ground state doublet was derived to be 117 ± 13 (statistical) ± 14 (systematic) nb/sr. The theoretical prediction of the cross section was consistent with the present result, validating DWIA calculation for hypernuclear yields. The present study proved the effectiveness of the (e,e'K+) reaction for future Lambda hypernuclear spectroscopy studies.
- Research Organization:
- Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- AC05-84ER40150
- OSTI ID:
- 920648
- Report Number(s):
- JLAB-PHY-03-240; DOE/ER/40150-4401; TRN: US0805333
- Country of Publication:
- United States
- Language:
- English
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