Spectroscopy of [superscript 9][subscript lambda]Li by electroproduction

Abstract

Background: In the absence of accurate data on the free two-body hyperon-nucleon interaction, the spectra of hypernuclei provides information on the details of the effective hyperon-nucleon interaction. Purpose: To obtain a high-resolution binding-energy spectrum for the [superscript 9]Be(e,e'K[superscript plus])[superscript 9][lambda] Li reaction. Method: Electroproduction of the hypernucleus [superscript 9][lambda] Li has been studied for the first time with sub-MeV energy resolution in Hall A at Jefferson Lab on a [superscript 9]Be target. In order to increase the counting rate and to provide unambiguous kaon identification, two superconducting septum magnets and a ring imaging Cherenkov detector were added to the Hall A standard equipment. Results: The cross section to low-lying states of [superscript 9][lambda] Li is concentrated within 3 MeV of the ground state and can be fit 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. The [lambda] separation energy, B[subscript lambda], of 8.36 [plus or minus] 0.08 (stat.) [plus or minus]0.08 (syst.) MeV was measured, in agreement with an earlier experiment.