Interference Effects in B - Decays to Flavor - Mixed Neutral Mesons Clues to Small Amplitudes and CP - Violation Harry

CP violation can be observed in B decays when a given process depends upon interference between two weak amplitudes which have different CP-violating phases. Since most weak decay diagrams have quark lines where each has a definite flavor label, neutral mesons which are flavor mixtures are particularly interesting. Different diagrams can contribute to the different flavor components of the meson, and the wave function itself provides interference. The total amplitude for the decay of a B meson consisting of a b quark and an antiquark denoted by ¯ q can be expressed as as the sum of three independent amplitudes with different flavor topologies[1]: where U denotes a quark of charge (+2/3), D a quark of charge (-1/3) and U b denotes the U quark produced in the initial b → U transition with the emission of the W −. The spectator tree diagram (QQ1) has all three flavors produced by the b decay present in the final state together with the spectator antiquark ¯ q. The spectator annihilation diagrams (QQ2a) and (QQ2b) have the spectator antiquark ¯ q annihilated either by the U b or the D quark produced in the tree diagram. These can arise from a weak annihilation diagram, a weak W-exchange diagram or a tree diagram followed by final state interactions. Note that (QQ2a) is allowed only if the spectator ¯ q is a ¯ c or ¯ u and that (QQ2b) is allowed only if the spectator ¯ q 0