Isgur‐Wise functions and the Lorentz group

Abstract

AbstractBjorken‐like sum rules have proven to be very powerful in constraining the derivatives of the Isgur‐Wise (IW) function. We expose here, adapted to the simpler case of the baryon transition Λb → Λc ℓ ν (j = 0 for the light could), that the reason behind these strong constraints is the general idea that the IW function is expressed in terms of scalar products of states of the light cloud in a Hilbert space, related by Lorentz transformations. This fact leads to strong constraints on their possible shape. Both Lorentz group and the sum rule approaches are equivalent.