B Decays -measurements and Predictions * 1 Basic Methods on Upsilon-4s Resonance

Hadronic decays of B mesons are reviewed. First, masses of B mesons and observed patterns together with physics behind them are discussed. Then the effective Hamiltonian responsible for major decays is presented and its practical applications are discussed in the context of factorization. Various tests of factorization are then studied. For rare decays, the focus is placed on Kπ, ππ final state and the penguin-mediated Xsγ. In general, the measurements are in excellent agreement with predictions of the standard model. 1 Basic Methods on Upsilon-4S Resonance Most of the data presented in the following are collected on the upsilon-4S resonance, and some basic experimental techniques are briefly described below. The B meson pair production cross section on the upsilon-4S resonance is roughly 1 nb; namely, an integrated luminosity of 1 fb would generate 1 million B meson pairs. The CLEO-II detector has logged about 1.2 fb of data thus generating 1.2 million B meson pairs. On the upsilon-4S resonance, light quark pairs (uu, dd, ss, and cc often referred to as the ‘continuum’) are also generated in addition to the B meson pairs. The cross section ratio of B meson pair to the continuum is roughly 1 to 2.5. The continuum is often a major background and in order to understand this component, data are taken right below the resonance (32 MeV below the peak) corresponding to about one half of the integrated luminosity taken on the resonance. When we want to plot a distribution of certain parameter for B meson pairs, we can subtract the distribution for the data taken off-resonance from that taken on-resonance (with a proper normalization). The distribution is then said to be ‘continuum subtracted’. At the upsilon-4S resonance, the B mesons are generated with definite energy and momentum given by EB = Ebeam = 5.289GeV, PB = 0.325GeV/c (1) ∗A talk given at ’B Physics at Hadron Colliders’, Snowmass 1993.