The most important part of the order αs2 corrections to the charm
component of the charged-current structure functions F2(x,Q2) and
F3(x,Q2) have been calculated. This calculation is based on the asymptotic
form of the heavy-quark coefficient functions corresponding to the higher order
corrections to the W-boson-gluon fusion process. These coefficient functions
which are in principle only valid for Q2≫m2 can be also used to
estimate the order αs2 contributions at lower Q2 values provided x<0.1. It turns out that the above corrections are appreciable in the large
Q2-region and they explain the discrepancy found for the structure functions
between the fixed-flavour scheme (FFS) and the variable-flavour-number scheme
(VFNS). These corrections also hamper the extraction of the strange-quark
density from the data obtained for the charged-current and the
electromagnetic-current processes.Comment: 45 pages LaTeX, 17 Postscript Figure