On the determination of sin2thetasub(w) in semileptonic neutrino interactions

It is shown that if sin2thetasub(w) is measured in semileptonic neutrino interactions then, contrary to a claim in the literature, the error due to unknown dynamical (higher-twist) corrections to the QCD parton model is small provided an isoscalar target is used. The largest contributions to sigmasub(nc) and sigmasub(cc) are related by isospin invariance alone. Neglecting heavy quarks and Kobayashi-Maskawa (KM) mixing, the parton model is only needed for very small terms and introduces an uncertainty in sin2thetasub(w) which is probably less than 1%. There is a much larger theoretical error due to uncertainties in the element Usub(cs) of the KM matrix and in the strange quark distribution. With the full range 0.80<=vertical strokeUsub(cs)vertical stroke<=0.98 which is allowed phenomenologically, these uncertainties give delta sin2thetasub(w)=+-0.008. There is also an error of +-0.004 due to uncertainties in vertical strokeUsub(dc)vertical stroke and vertical strokeUsub(du)vertical stroke. (orig.)