https://doi.org/10.1140/epjc/s10052-020-08615-2
Regular Article - Theoretical Physics
Sum rule for the Compton amplitude and implications for the proton–neutron mass difference
1
Albert Einstein Center for Fundamental Physics, Institut für theoretische Physik, Universität Bern, Sidlerstrasse 5, 3012, Bern, Switzerland
2
Helmholtz-Institut für Strahlen- und Kernphysik (Theorie) and Bethe Center for Theoretical Physics, Universität Bonn, Nussallee 14-16, 53115, Bonn, Germany
Received:
13
August
2020
Accepted:
29
October
2020
Published online:
5
December
2020
The Cottingham formula expresses the leading contribution of the electromagnetic interaction to the proton-neutron mass difference as an integral over the forward Compton amplitude. Since quarks and gluons reggeize, the dispersive representation of this amplitude requires a subtraction. We assume that the asymptotic behaviour is dominated by Reggeon exchange. This leads to a sum rule that expresses the subtraction function in terms of measurable quantities. The evaluation of this sum rule leads to 
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© The Author(s) 2020
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