Influence of the Dirac sea on proton electromagnetic knockout

We use the relativistic distorted-wave impulse approximation (RDWIA) to study the effects of negative-energy components of Dirac wave functions on the left-right asymmetry for $(e,{e}^{'}p)$ reactions on $^{16}\mathrm{O}$ with $0.2\ensuremath{\le}{Q}^{2}\ensuremath{\le}0.8$ and $^{12}\mathrm{C}$ with $0.6\ensuremath{\le}{Q}^{2}\ensuremath{\le}1.8\phantom{\rule{0.3em}{0ex}}(\text{GeV}/c){}^{2}$. Spinor distortion is more important for the bound state than for the ejectile and the net effect decreases with ${Q}^{2}$. Spinor distortion breaks Gordon equivalence and the data favor the CC2 operator with intermediate coupling to the sea. The left-right asymmetry for ${Q}^{2}\ensuremath{\lesssim}1.2\phantom{\rule{0.3em}{0ex}}(\text{GeV}/c){}^{2}$ is described well by RDWIA calculations, but at ${Q}^{2}=1.8\phantom{\rule{0.3em}{0ex}}(\text{GeV}/c){}^{2}$ the observed variation with missing momentum is flatter than predicted.