Search for double-Λ hypernuclei formation via (Ξ-,12C)atom→ΛΛ12B+n -: art. no. 027601

Measurement of the energy of neutrons in coincidence with the production of free Xi(-) hyperons can be used to determine the masses of B-12(Lambda Lambda) hypernuclear states and branching ratios of their formation from (Xi(-), C-12)(atom) --> B-12(Lambda Lambda)+n. The E885 Collaboration utilized the Alternating Gradient Synchrotron 1.8 GeV/c K- beam incident on a diamond target to accumulate the largest-to-date data sample of (K-,K+) events. A total of about 3x10(5) (K-,K+) events have been collected and analyzed. The neutron spectrum shows no apparent peaks from the neutron-emission channel of double-Lambda hypernuclear formation from (Xi(-), C-12)(atom) decay. The upper limit on the branching ratio of the above process has been set to be at or below 4% in the region of expected neutron energies.