2017/12/31 by Vadim Lensky, Franziska Hagelstein, Vladimir Pascalutsa +1
Physics and Astronomy · #Compton scattering #Electron #Nuclear physics #Nuclear physics research studies #Nucleon #Particle physics #Particle physics theoretical and experimental studies #Physics #Quantum Chromodynamics and Particle Interactions #Quantum chromodynamics #Sum rule in quantum mechanics #hep-ph #nucl-ex #nucl-th
paper · pdf · doi:10.1103/physrevd.97.074012
published as Phys. Rev. D 97, 074012 (2018) · 22 pages, 5 figures, minor modifications, published version
openalex publication_date 2018/04/12 · arxiv created 2018/04/20 · arxiv updated 2018/04/25 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We derive two new sum rules for the unpolarized doubly virtual Compton scattering process on a nucleon, which establish novel low-Q2 relations involving the nucleon's generalized polarizabilities and moments of the nucleon's unpolarized structure functions F1(x,Q2) and F2(x,Q2). These relations facilitate the determination of some structure constants which can only be accessed in off-forward doubly virtual Compton scattering, not experimentally accessible at present. We perform an empirical determination for the proton and compare our results with a next-to-leading-order chiral perturbation theory prediction. We also show how these relations may be useful for a model-independent determination of the low-Q2 subtraction function in the Compton amplitude, which enters the two-photon-exchange contribution to the Lamb shift of (muonic) hydrogen. An explicit calculation of the \mathrm\ensuremathΔ(1232)-resonance contribution to the muonic-hydrogen 2P\ensuremath-2S Lamb shift yields \ensuremath-1\ifmmode±\else\textpm\fi1 \ensuremathμeV, confirming the previously conjectured smallness of this effect.