Theory Uncertainty in Extracting the Proton's Weak Charge: White Paper

We review the state-of-the-art and address open questions relative to the theory uncertainty of the $\gamma-Z$ box contribution to the $A_{PV}$ measurement within the QWEAK experiment at Jefferson Lab. This white paper summarizes the contributions by participants and discussion sessions on this topic within the MITP Workshop on Precision Electroweak Physics held in Mainz, Germany, September 23 - October 11, 2013 \url{http://indico.cern.ch/conferenceDisplay.py?confId=248072