A cosmic-ray nuclear event of abnormally high multiplicity and large transverse momenta

Abstract

We give a description of a nuclear event of new character observed in an emulsion chamber exposed on Mt. Chacaltaya. The interaction has its vertex within the chamber and contains 40 γ-rays, whose energies sum up to ∼42 TeV. The most remarkable feature of the event are: 1) Abnormally large transverse momenta. The average transverse momentum of the γ-rays is ∼0.5 GeV/c. 2) Abnormally high transverse-momentum density. That of the γ-rays is (70÷90) GeV/c per unit log tgϑ interval. 3) Multijetlike angular structure. At least three structures are observed. 4) Noncoplanarity. The γ-ray momentum distribution deviates appreciably from a coplanar one. If a fireball picture is adopted, the event can be interpreted as a production of a giant fireball, out of whose rest energy an energy of (60÷80) GeV is liberated in the form of γ-rays, and which decays into hadrons through smaller fireballs. The highest-energy γ-ray pair starts in an empty space within the chamber, suggesting that they come from a parent particle with a lifetime of the order of 10−13 s.