Electromagnetic contribution to charge symmetry violation in parton distributions

• Main Authors: X.G. Wang, A.W. Thomas, R.D. Young
• Format: Article
• Language: English
• Published: Elsevier 2016-02-01
• Series: Physics Letters B
• Subjects: Charge symmetry; Parton distributions; Electromagnetic correction
• Online Access: http://www.sciencedirect.com/science/article/pii/S0370269315010102
• ISSN: 0370-2693; 1873-2445

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.