title: Hypernuclear fine structure in (9)(lambda)Be.
abstract: With a germanium detector array (Hyperball), we observed two gamma-ray peaks corresponding to the two transitions (5/2(+)-->1/2(+) and 3/2(+)-->1/2(+)) in the (9)(Lambda)Be hypernucleus which was produced by the 9Be(K-,pi(-)) reaction. The energies of the gamma rays are 3029 +/- 2 +/- 1 keV and 3060 +/- 2 +/- 1 keV. The energy difference was measured to be 31.4(+2.5)(-3.6) keV, which indicates a very small Lambda-spin-dependent spin-orbit force between a Lambda and a nucleon. This is the smallest level splitting by far ever measured in a hypernucleus.
authors.affiliation: Department of Physics, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Akikawa
authors.forename: S
authors.initials: S
authors.lastname: Ajimura
authors.forename: R E
authors.initials: RE
authors.lastname: Chrien
authors.forename: P M
authors.initials: PM
authors.lastname: Eugenio
authors.forename: G B
authors.initials: GB
authors.lastname: Franklin
authors.forename: J
authors.initials: J
authors.lastname: Franz
authors.forename: L
authors.initials: L
authors.lastname: Gang
authors.forename: K
authors.initials: K
authors.lastname: Imai
authors.forename: P
authors.initials: P
authors.lastname: Khaustov
authors.forename: M
authors.initials: M
authors.lastname: May
authors.forename: P H
authors.initials: PH
authors.lastname: Pile
authors.forename: B
authors.initials: B
authors.lastname: Quinn
authors.forename: A
authors.initials: A
authors.lastname: Rusek
authors.forename: J
authors.initials: J
authors.lastname: Sasao
authors.forename: R I
authors.initials: RI
authors.lastname: Sawafta
authors.forename: H
authors.initials: H
authors.lastname: Schmitt
authors.forename: H
authors.initials: H
authors.lastname: Tamura
authors.forename: L
authors.initials: L
authors.lastname: Tang
authors.forename: K
authors.initials: K
authors.lastname: Tanida
authors.forename: L
authors.initials: L
authors.lastname: Yuan
authors.forename: S H
authors.initials: SH
authors.lastname: Zhou
authors.forename: L H
authors.initials: LH
authors.lastname: Zhu
authors.forename: X F
authors.initials: XF
authors.lastname: Zhu