DISPERSIVE BOUNDS ON THE SHAPE OF $\Lambda_b\to \Lambda_b l\bar{\nu}_l$ FORM FACTORS

Abstract

We derive a theoretically allowed domain for the charge radius ρ and the curvature c of the Isgur–Wise function describing the decay [Formula: see text]. Our method uses crossing symmetry, dispersion relations and analyticity in the context of the heavy quark effective theory (HQET), but is independent of the specifics of any given model. The experimentally determined values of the ϒ masses have been used as input information. The results are of interest for testing different models employed to calculate the heavy baryon form factors which are used for the extraction of |Vcb| from experimental data.