B<inf>K</inf> in the chiral limit within the 1/N<inf>c</inf> expansion

I report on a recent calculation done in collaboration with E. de Rafael [7] of the invariant B̂K factor of K0-K0 mixing in the chiral limit and to next-to- leading order in the 1/Nc expansion. This calculation is, to the best of our knowledge, the first example of a calculation of B̂K in which there is an explicit analytic cancellation of the μ renormalization scale and the scheme dependence between the Wilson coefficient and the corresponding kaon matrix element. I try to emphasize the ideas involved in the approach and how the method could be applied to other physical situations, rather than the details of the numerical analysis for which I refer the reader to ref. [7]. © 2001 Elsevier Science B.V. All rights reserved.