Eur. Phys. J. C 19, 339-349
DOI: 10.1007/s100520100605

A variable flavour number scheme for charged current heavy flavour structure functions

R.S. Thorne¹ and R.G. Roberts<sup>2

1</sup>  Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge, CB3 0HE, UK
²  Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, OX11 0QX, UK

(Received: 3 November 2000 / Revised version: 16 January 2001 / Published online: 15 March 2001 -© Springer-Verlag 2001)

Abstract
The Thorne-Roberts variable flavour number scheme (VFNS) for heavy quarks is presented in detail for the specific case of charged current DIS. As in neutral current DIS this provides a smooth extrapolation from the fixed flavour number scheme (FFNS) appropriate at low Q² to the zero-mass variable flavour number scheme (ZM-VFNS) appropriate as , and differs from alternative versions of a VFNS by the definition of the coefficient functions at each order, and the strict ordering of the expansion in . However, there are subtle differences from the neutral current case which are addressed here. We discuss both the LO and NLO expressions, the latter unfortunately requiring some (minimal) modelling due to the current lack of some necessary FFNS coefficient functions.

© Società Italiana di Fisica, Springer-Verlag 2001