An observation of the spin dependence of synchrotron radiation intensity

First Observation of the Parity Violating Asymmetry in Moller Scattering

“…Another potential correction to the Moller asymmetry comes from synchrotron photons, because they can acquire an asymmetry if the beam has any transversely polarized electrons [34,35]. Although, the E158 beam should be polarized purely longitudinally, vertical magnets present in the beamline before the beam reaches the E158 spectrometer can impart some small amount of transverse polarization to the beam.…”

A Precision Measurement of the Weak Mixing Angle in Moller Scattering at Low Q^2

“…The power emitted by an electron beam traversing a magnet has an asymmetry related to the amount of spin polarization in the direction of the magnetic field [45,59]. The power in a synchrotron beam is given by…”

“…The energy absorbed from actual signal electrons is expected to be about 150 Watts, meaning that synchrotron radiation is roughly 10% of the energy of the lumi signal at the face of the detector [64]. By itself this is a large dilution factor, but the main issue of concern is that synchrotron radiation can have helicity-correlated asymmetries of its own [45,59,65,66]. Asymmetries up to the level of 600 ppb could be generated in the synchrotron spectrum from the E158 spectrometer.…”

A Spin-Light Polarimeter for Multi-GeV Longitudinally Polarized Electron Beams

“…The spin dependence of the SR was verified at the VEPP-4 storage ring in Novosibirsk [17], using a 3 pole wiggler magnet (called a magnetic snake). The intensity of the SR produced by the wiggler for transversely polarized electrons was monitored while the beam was periodically depolarized using a RF field.…”