Search

A hybrid emulsion experiment E373 at KEK has been carried out to study doubly strange nuclear system. By the 8% data analysis of all, one twin single-Λ hypernuclei event and two events of double-Λ hypernucleus have been successfully detected. The twin single-Λ event is uniquely interpreted as Ⅺ−+14N→Λ5He+Λ5He+4He+n for the first time. In the first double-Λ hypernucleus event, “Demachi-Yanagi,” it is interpreted as Ⅺ−+12C→ΛΛ10Be* (or ΛΛ10Be*)+t. The second double-Λ hypernucleus event, “NAGARA,” shows a clearly recognized topology and the interpretation is unique as Ⅺ−+12C→ΛΛ6He+4He+t, ΛΛ6He→Λ5He+π−+p, Λ5He→p+d+2n etc. By the preliminary result of the ΛΛ6He, the attractive ΛΛ interaction has been confirmed with the ΔBΛΛ∼1 MeV.

Recent results from a hybrid emulsion experiment in the Fermilab wide‐band neutrino beam of the measurement of the lifetimes of the charmed D+, Do and F+ mesons and Λc+ charmed baryon are presented.

Technical aspects of small emulsion chamber are discussed. Emulsion chamber is a detector which consists of nuclear emulsion plates and other light or heavy material plates. While a pure emulsion stack is likened to a micro bubble chamber, it could be compared to a complex counter detector assembly with super high spatial resolving power. It is possible to measure particle momenta by relative scattering method and trace back γ ray cascades to vertices a few centimeters away. Charged secondary tracks could be examined for sudden changes in direction several centimeters from production vertices. ’’Invention’’ of the emulsion chamber enabled one to extend the power of pure emulsions to study very high energy interactions to tens of TeV, and it opend a new windnow for search of short‐lived particles.