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Elastic s-wave scattering phase shifts and |Vub| from lattice calculations of form factors for exclusive semileptonic decays

Presenter: Jonathan Flynn — University of Southampton

Jonathan M Flynn and Juan Nieves

We show how lattice, calculations of the scalar form factors in semileptonic pseudoscalar-to-pseudoscalar decays can be used to extract information about the corresponding elastic s-wave scattering channels. For this purpose, we use the Omnes representation of the scalar form factor. We find values for the scattering lengths mπa = 0.179(17)(14), 0.26(26) and 0.29(4) for elastic s-wave isospin-1/2 Kπ, Bπ and Dπ channels respectively. We also determine phase shifts. For the DK channel we find hints that there is a bound state which can be identified with the recently discovered Ds0+(2317). More details can be found in PRD75 (2007) 074024.

The Omnes representation can also be used for the vector form factor and provides a well-motivated parametrisation to be used when combining experimental branching fraction data with lattice form factor calculations to extract |Vub| from exclusive semileptonic B to pi decays.