Precision electron beam polarimetry for next generation nuclear physics experiments

Abstract

Polarized electron beams have played an important role in scattering experiments at moderate to high beam energies. Historically, these experiments have been primarily targeted at studying hadronic structure -from the quark contribution to the spin structure of protons and neutrons, to nucleon elastic form factors, as well as contributions to these elastic form factors from (strange) sea quarks. Other experiments have aimed to place constraints on new physics beyond the Standard Model. For most experiments, knowledge of the magnitude of the electron beam polarization has not been a limiting systematic uncertainty, with only moderately precise beam polarimetry requirements. However, a new generation of experiments will require extremely precise measurements of the beam polarization, significantly better than 1%. This paper will review standard electron beam polarimetry techniques and possible future technologies, with an emphasis on the ever-improving precision that is being driven by the requirements of electron scattering experiments.

Signatures of linear Breit-Wheeler pair production in polarized $γγ$ collisions

“…The yield and polarization stabilities are estimated when the divergence angle and the polarization of the γ-photon beam change and uniform results are obtained (see [48]). In terms of the polarization detection, the e ± polarimetry technology has achieved a high precision 1%, e.g., Compton transmission polarimetry [37][38][39] and Mott polarimetry [56][57][58], which are both applicable at the energy of 0.1 − 10 MeV and can response the current as low as 100µA [56,57].…”

Generation of polarized particle beams at relativistic laser intensities

“…Depending on the electron beam energy, which determines the analyzing power as well as experimental access to the scattering products, one of the following spin-dependent QED processes can be used for electron polarimetry [73] .…”

Polarized Atomic Hydrogen Target at MESA

“…Laser-Compton backscattering would offer similar advantages but is difficult to use here because of the low beam energy at the P2-experiment. A discussion of the systematic uncertainties of the polarimeters mentioned in this section can be found in [9].…”