Leon Lederman and coworkers studied the production of muon anti-muon pairs in 1977. The mass distribution of the m+m- system showed a clear peak at a mass of 9.5 GeV/c2 and another one at 10.1 GeV/c2. The mass width was measured to be less than 0.6 GeV. The new particle, ¡, consists of a new quark anti-quark pair. The new quark is called "beauty" quark (sometimes "bottom"). Most often it is referred to as the b-quark. The key to anti-matter can perhaps be found in the interactions between quarks in this system.
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