Abstract :
The main application of heavy quark effective theory (HQET) and of soft collinear effective theory (SCET) is in establishing factorization theorems for exclusive and semi-inclusive decays of heavy mesons. However, the calculation of the soft factors from the HQET or SCET factorization relations is, as usual, impeded by the non-perturbative aspect of the strong interactions. In the hope of gaining some insights into some of these quantities we compute them in the ʹt Hooft model. We find that the B-meson shape function is exactly given by the square of the B-meson light-cone wave-function. The structure of the image soft function is more complicated: it is given by the product of wave-functions or by a resonant sum depending on the kinematics. The result simplifies dramatically in the chiral limit, where it can be compared with general arguments based on heavy meson-chiral perturbation theory. No attempt is made to use these results for applications to phenomenology.
