Evidence for a new particle with naked «beauty» and for its associated production in high-energy (pp) interactions

Abstract

Evidence is reported for the existence, with six-standard-deviation significance, of a new particle: the heaviest baryon observed so far, whose mass is measured to bem=(5425−75+175) MeV/c2. Its width is compatible with zero. It is electrically neutral and it decays into a proton, a Do and a π–. This particle is produced in association with a hadronic state whose semi-leptonic decay contains a positive electron. The partial cross-section for the observed effect is Δσ=(3.8±1.2)·10−35 cm2. The interpretation of these results is in terms of the associated production of naked-«beauty» states in (pp) interactions at\(\sqrt 8 = 62 GeV c.m.\) GeV c.m. energy. The new particle is identified as the first «beauty»-flavoured baryon with quark composition (udb),i.e. the Λb0. The discrimination power of the experiment against «known» physics is of the order of 10−10.