2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/184146The correlation function of a $V-A$ current with a $V+A$ current is discussed within the framework of QCD in the limit of a large number of colours $N_c$. Applications to the evaluation of chiral condensates of dimension six and higher, as well as to the matrix elements of the $Q_7$ and $Q_8$ electroweak penguin operators are discussed. A critical comparison with previous determinations of the same parameters has also been made.Layout modified, size of first figure correctedHigh Energy Physics - Phenomenologytext