# Archive: S2: Accomplishments of the second funding period

In the second funding period we focus on the following areas of research:
• Scalar polarizabilities of the proton from both the beam asymmetry $$\Sigma_3$$ and differential cross section in Compton scattering ($$\gamma p \to \gamma p$$) below pion threshold with an unpolarized hydrogen target.  Results from a proof-of-principle test measurement have been published [10.1140/epja/i2017-12203-0] [A2 Collaboration].
• Spin polarizabilities of the proton via Compton scattering in the $$\Delta(1232)$$ region, both from the beam-target asymmetries $$\Sigma_{2x}$$ and $$\Sigma_{2z}$$ with a polarized hydrogen target, and from the beam asymmetry $$\Sigma_3$$ from an unpolarized target. Results from the first beam-target asymmetry have been published [10.1103/PhysRevLett.114.112501] [A2 Collaboration].

Proton Compton scattering beam-target asymmetry $$\Sigma_{2x}$$ along with dispersion relation theory curves, taken from [10.1103/PhysRevLett.114.112501].

• A model-independent partial-wave analysis of Compton scattering data, with the aim of extracting the static and dynamic polarizabilities of the proton, has been developed  [10.1016/j.physletb.2018.04.066], and will be used to interpret the new data.
• Polarized and unpolarized active target developments to access both proton and neutron observables [10.22323/1.243.0005] [A2 Collaboration].
• Neutron polarizabilities from Compton scattering and inclusive measurements on the deuteron and helium [10.22323/1.253.0092] [A1 and A2 Collaborations].
• Precise measurements of the electrodisintegration of the deuteron at small momentum transfers [A1 Collaboration].
• Theoretical description of the timelike nucleon structure in the process of di-lepton photoproduction. Feasibility studies for di-lepton photoproduction experiments [A2 Collaboration].
• Feasibility studies for polarizability measurements at the upcoming MESA facility.
• Chiral effective-field theory for nucleon and light-nuclear polarizabilities.  Calculations of the nucleon and nuclear polarizability effects in muonic atoms.