Improved Unitarity Bounds for B -> Pi Decays

Abstract

We obtain model independent bounds for the form factors which arise in semileptonic B -> Pi decays. To this end we derive a theoretical restriction for possible combinations of the value of the form factor and its derivatives at the endpoint region. These restrictions are then used as an input in a - slightly modified - general formalism, which has already been deduced and applied in earlier publications. Our results can be used to set constraints on the form factors which have to be obeyed by all model dependent parametrizations.

Comments: 20 pages, 10 Postscript figures, uses espf. Minor modifications, two references added and aknowledgements changed. The complete paper, including figures, is also available via anonymous ftp at ftp://ttpux2.physik.uni-karlsruhe.de/ , or via www at http://www-ttp.physik.uni-karlsruhe.de/cgi-bin/preprints