CESR shows bare‐bottomed mesons
In its first year of operation, the Cornell electron–positron storage ring, CESR, has provided strong evidence for the existence of a fifth quark flavor. The three narrow upsilon mesonic states near 10 GeV, first seen at Fermilab in 1977 and 1978, had offered the initial experimental evidence for a hadronic building block heavier than the charmed quark (see PHYSICS TODAY, October 1977, page 17 and January 1979, page 17). The Γ, Γ′ and Γ″ were generally believed to be bound states of a massive new “bottom” quark, b, and its antiparticle.