Reweighting of the form factors in exclusive $B \rightarrow X \ell \nu_{\ell}$ decays

Abstract.A form factor reweighting technique has been elaborated to permit relatively easy comparisons between different form factor models applied to exclusive $B \rightarrow X \ell \nu_{\ell}$ decays. The software tool developed for this purpose is described. It can be used with any event generator, three of which were used in this work: ISGW2, PHSP and FLATQ2, a new powerful generator. The software tool allows for an easy and reliable implementation of any form factor model. The tool has been fully validated with the ISGW2 form factor hypothesis. The results of our present studies indicate that the combined use of the FLATQ2 generator and the form factor reweighting tool should play a very important role in future exclusive |Vub| measurements, with largely reduced errors.