Our group’s latest result is a paper published in the European Physical Journal A on radiative corrections for specific type of electron-proton scattering experiment, called a Super Rosenbluth experiment. Elastic electron-proton scattering experiments are useful for learning about how the charge and magnetism of a proton are distributed within its volume. At low electron beam energies, it makes sense for the experiment to detect the scattered electron, since very little energy is transferred to the proton, since it is comparatively heavy. At higher beam energies, there is a significant “kick” given to the proton, and experiments can be conducted in which the electron and proton are detected at the same time, that is, in coincidence. In a super-Rosenbluth experiment, only the kicked proton is detected. Proponents of this technique have claimed many benefits, one of which is the supposed reduction in complexity of radiative corrections.
To test this, we simulated traditional electron detection and super-Rosenbluth experiments using two different radiative corrections models. The first model employed the peaking approximation, an approximation that charged particles will only radiate energy in their direction of motion. The second model did not make this approximation. We found that when using the peaking approximation, radiative corrections were indeed smaller and less kinematically-dependent when performing a super-Rosenbluth experiment.
By contrast, when using a model that avoided the peaking approximation, radiative corrections were significantly larger.
We were able identify that the larger radiative tail was caused by radiation from the proton, rather than from the electron. Specifically, if the proton were to radiate a photon in the direction of an elastically scattered electron, there could be a large enhancement in cross section.
This reaction is not modeled in the peaking approximation. For that reason, we conclude that the peaking approximation is dubious for super-Rosenbluth experiments.
Undergraduate Quinn Stefan began working on this project as part of her Luther Rice fellowship in 2023.