期刊
PHYSICAL REVIEW D
卷 97, 期 7, 页码 -出版社
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevD.97.074012
关键词
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资金
- Deutsche Forschungsgemeinschaft (DFG) in part through the Collaborative Research Center [The Low-Energy Frontier of the Standard Model] [SFB 1044]
- Cluster of Excellence [Precision Physics, Fundamental Interactions and Structure of Matter (PRISMA)]
- Swiss National Science Foundation
We derive two new sum rules for the unpolarized doubly virtual Compton scattering process on a nucleon, which establish novel low-Q(2) relations involving the nucleon's generalized polarizabilities and moments of the nucleon's unpolarized structure functions F-1 (x, Q(2)) and F-2 (x, Q(2)). 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-Q(2) 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 Delta(1232)-resonance contribution to the muonic-hydrogen 2P - 2S Lamb shift yields -1 +/- 1 mu eV, confirming the previously conjectured smallness of this effect.
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