Width effects in resonant three-body decays: B decay as an example

For three-body hadron decays mediated by intermediate resonances with large widths, we show how to properly extract the quasi-two-body decay rates for a meaningful comparison with the corresponding theoretical estimates, using several B decays as explicit examples. We compute the correction factor from finite width effects in the QCD factorization approach, and make a comparison with that using the experimental parameterization in which the momentum dependence in the weak dynamics is absent. Although the difference is generally less than 10% for tensor and vector resonances, it can be as large as (25−40)% for scalar resonances. Our finding can in fact be applied to general quasi-two-body decays.