– 1– Branching Ratios of Ψ(2s) and Χ C0,1,2

In this edition, the treatment of the branching ratios of the ψ(2S) and χc0,1,2 has undergone an important restructuring. When measuring a branching ratio experimentally, it is not always possible to normalize the number of events observed in the corresponding decay mode to the total number of particles produced. Therefore, the experimenters sometimes report the number of observed decays with respect to another decay mode of the same or another particle in the relevant decay chain. This is actually equivalent to measuring combinations of branching fractions of several decay modes. To extract the branching ratio of a given decay mode, the collaborations use some previously reported measurements of the required branching ratios. However, the values are frequently taken from the Review of Particle Physics (RPP), which in turn uses the branching ratio reported by the experiment in the following edition, giving rise either to correlations or to plain vicious circles. One of these inconsistencies within the ψ(2S) decays was reported in Ref. 9. To obtain the branching ratios of the decay modes ψ(2S) → J/ψ(1S)π+ π−, ψ(2S) → J/ψ(1S)π0 π0, and ψ(2S) → J/ψ(1S) η, E760 Collaboration [2] used the value of B(ψ(2S)→ J/ψ(1S) anything) given in Ref. 6, obtained with a fit that included the above decays. The values obtained in this way in Ref. 2 were subsequently used in the 1998 edition of RPP [7] as new entries in the same fit. A more subtle correlation, among others, was pointed out in Ref. 5. BES Collaboration [3] obtained the value of B(χc0 → p p) in e+e− collisions from the number of observed decays ψ(2S)→ γ χc0 → γ p p, and the total number of ψ(2S) produced, which was estimated in turn from the observed number of decays of the type ψ(2S) → J/ψ(1S)π+ π− [4]. To this end, they used the values of the branching ratios ofψ(2S)→ J/ψ(1S)π+ π− and ψ(2S)→ γ χc0 given in the 1996 edition of RPP [6]. On the other hand, in p p collision experiments (e.g., E835 Collaboration [1]), the value of B(ψ(2S) → γ χc0) was