Working Group 6: Default Branching Ratios and Background Information

If you want to use an unknown or poorly known BR, please tell us! We want to avoid having different assumptions on these numbers in different chapters of THE BOOK.

Tables with experimental and theoretical input

1. B -> pi pi

BR(B0 -> pi+ pi-) = 1.2*10^-5

This is kept for historical reasons. The uncertainty is still very large, a value of 0.5*10^-5 should be considered as a possible worse (not worst!) case.

2. B -> psi K_s

BR(B0 -> J/psi K_s -> l+ l- K_s) = 2.9*10^-5

This is the product branching fraction including the J/psi decay into a lepton pair. This is the quantity measured by previous experiments, and the one relevant for BABAR. The uncertainty in BR(J/psi -> l+ l-) is irrelevant. It is for one channel, i.e. e+ e- or mu+ mu-. The total accessible states at 100% efficiency are twice that fraction (assuming K_s is reconstructed in pi+ pi- and pi0 pi0).

The number given assumes (a) equal B+ B- and B0 B0 production on the Y(4S) and (b) equal BR(B+ -> J/psi K+) and BR(B0 -> J/psi K0). If one drops assumption (b), the best estimate is
BR(B0 -> J/psi K_s -> l+ l- K_s) = 2.3*10^-5
with errors of 0.6*10^-5, i.e. well compatible with our default value.

comments or contributions welcome: just send email to Roland or use the hypernet BABAR Discussion group 6.

Last update: 09 Dec 96, RW.