An enhancement has been observed in the inclusive cross section for direct single electrons produced in e*e~ annihilations at the T(4S). This is interpreted as evidence for a new weakly decaying particle, the B meson. A branching ratio for B -Xev of ll3± 3 (±3)]% is inferred, where the first set of errors is statistical and the estimated systematic error is enclosed in parentheses.PACS numbers: 14.40.Pe, 13.20.Jf, 13.65.+ iThe recently discovered resonance in e*e~ annihilations at 10.55 GeV total energy 1 ' 2 has a natural interpretation as the T (4S) bound state of bfi quarks. Its width indicates that this state is above the threshold for producing pairs of B mesons, bound states of b quarks with u or i? quarks, and has as its dominant decay mode BB meson final states. 3 The existence of a new, weakly decaying flavor can be inferred from the semileptonic decay B-+Xlv and the branching ratio (BR) for this 84

Three narrow resonances have been observed ine+e' annihilation into hadrons at total energies between 9.4 and 10.4 GeV. Measurements of mass spacings and ratios of lepton pair widths support the interpretation of these "T" states as the lowest triplet-5 levels of the bb quark-antiquark system. PACS numbers: 13.65.+iWe report here on the first results from the CLEO detector at the Cornell Electron Storage Ring (CESR). CLEO is a magnetic detector built around a 1.05-m-radius, 3-m-long solenoid coil producing a magnetic field parallel to the beams (see Fig. 1). Charged particles are observed and their momenta measured over a solid angle of 0.90 X47T sr in a cylindrical drift chamber occupying most of the field volume. A smaller cylindrical proportional chamber immediately surrounding the beam pipe provides improved resolution along the beam axis. Outside the 0.9-radiationlength thick aluminum solenoid coil are scintillation counters 2.2 m from the beam line (covering 1108

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