2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/203251Due to the weak current non-conservation the diffractive excitation of charm and strangeness dominates the longitudinal structure function $F_L(x,Q^2)$ of neutrino DIS at small Bjorken $x$. Based on the color dipole BFKL approach we report quantitative predictions for this effect in the kinematical range of the CCFR/NuTeV experiment. We comment on the relevance of our findings to experimental tests of PCAC.13 pages, 3 figures, Version to appear in JETP LettersHigh Energy Physics - Phenomenologytext