Search

We propose to determine the magnetic dipole polarizability of the proton from the beam asymmetry of low-energy Compton scattering based on the fact that the leading non-Born contribution to the asymmetry is given by the magnetic polarizability alone; the electric polarizability cancels out. The beam asymmetry thus provides a simple and clean separation of the magnetic polarizability from the electric one. Introducing polarizabilities in a Lorentz-invariant fashion, we compute the higher-order (recoil) effects of polarizabilities on beam asymmetry and show that these effects are suppressed in forward kinematics. With the prospects of precision Compton experiments at the Mainz Microtron and High Intensity Gamma Source facilities in mind, we argue why the beam asymmetry could be the best way to measure the elusive magnetic polarizability of the proton. [ABSTRACT FROM AUTHOR]

Nonlinear Compton scattering is a promising source of bright gamma rays. Using readily available intense laser pulses to scatter off the energetic electrons, on the one hand, allows us to significantly increase the total photon yield, but on the other hand, leads to a dramatic spectral broadening of the fundamental emission line as well as its harmonics due to the laser pulse shape induced ponderomotive effects. In this Letter we propose to avoid ponderomotive broadening in harmonics by using the polarization gating technique--a well-known method to construct a laser pulse with temporally varying polarization. We show that by restricting harmonic emission only to the region near the peak of the pulse, where the polarization is linear, it is possible to generate a bright narrow bandwidth comb in the gamma region. [ABSTRACT FROM AUTHOR]

Searches for pseudoscalar axionlike-particles (ALPs) typically rely on their decay in beam dumps or their conversion into photons in haloscopes and helioscopes. We point out a new experimental direction for ALP probes via their production by the intense gamma ray flux available from megawatt-scale nuclear reactors at neutrino experiments through Primakoff-like or Compton-like channels. Low-threshold detectors in close proximity to the core will have visibility to ALP decays and inverse Primakoff and Compton scattering, providing sensitivity to the ALP-photon and ALP-electron couplings. We find that the sensitivity to these couplings at the ongoing MINER and various other reactor based neutrino experiments, e.g., CONNIE, CONUS, ν-cleus, etc., exceeds existing limits set by laboratory experiments and, for the ALP-electron coupling, we forecast the world's best laboratory-based constraints over a large portion of the sub-MeV ALP mass range. [ABSTRACT FROM AUTHOR]