Precision Rosenbluth Measurement of the Proton Elastic Form Factors

We report the results of a new Rosenbluth measurement of the proton electromagnetic form factors at $Q^2$ values of 2.64, 3.20, and $4.10{\mathrm{GeV}}^2$. Cross sections were determined by detecting the recoiling proton, in contrast to previous measurements which detected the scattered electron. Cross sections were determined to 3%, with relative uncertainties below 1%. The ratio ${\mu }_p{G}_E/G_M$ was determined to 4%–8% and showed ${\mu }_p{G}_E/G_M\approx 1$. These results are consistent with, and much more precise than, previous Rosenbluth extractions. They are inconsistent with recent polarization transfer measurements of similar precision, implying a systematic difference between the techniques.