Search for superfragments and measurement of the production of hyperfragments in neutrino-nucleus interactions

A systematic search for superfragments (charmed nuclei) has been performed in 22 200 neutrino-emulsion interactions obtained with the CHORUS experiment making use of automatic off-line image analysis. The absence of candidates provides an upper limit for the superfragment production rate of 1.9×10−4 (90% C.L.) relative to neutrino charged-current interactions at an average neutrino energy of 27 GeV. In the same analysis 28 hyperfragment decays were found. For the first time, a production rate of hyperfragments in neutrino-emulsion interactions was obtained. The value of the hyperfragment production rate relative to the neutrino charged-current cross-section was found to be (2.0±0.4(stat)±0.3(syst))×10−3.