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We report a calculation of the combined effect of photon radiation and quark mass differences on charge symmetry violation (CSV) in the parton distribution functions of the nucleon. Following a recent suggestion of Martin and Ryskin, the initial photon distribution is calculated in terms of coherent radiation from the proton as a whole, while the effect of the quark mass difference is based on a recent lattice QCD simulation. The distributions are then evolved to a scale at which they can be compared with experiment by including both QCD and QED radiation. Overall, at a scale of 5 GeV2, the total CSV effect on the phenomenologically important difference between the d and u-quark distributions is some 20% larger than the value based on quark mass differences alone. In total these sources of CSV account for approximately 40% of the NuTeV anomaly.

Abstract: In light of the recent discovery of the importance of the isovector EMC effect for the interpretation of the NuTeV determination of , it seems timely to reassess the central value and the errors on this fundamental Standard Model parameter derived from the NuTeV data. We also include earlier work on charge symmetry violation and the recent limits on a possible asymmetry between s and quarks. With these corrections we find a revised NuTeV result of , which is in excellent agreement with the running of predicted by the Standard Model. As a further check, we find that the separate ratios of neutral current to charge current cross-sections for neutrinos and for antineutrinos are both in agreement with the Standard Model, at just over one standard deviation, once the corrections described here are applied. [ABSTRACT FROM AUTHOR]