Llanes Estrada, Felipe JoséGorchtein, MikhailSzczepaniak, Adam P2023-06-192023-06-192013-05-031050-294710.1103/PhysRevA.87.052501https://hdl.handle.net/20.500.14352/33382© 2013 American Physical Society. We thank Stan Brodsky for suggesting that we reexamine this issue and for various useful comments. This work is supported by US DOE Grant No. DE-FG0287ER40365, German SFB 1044, and Spanish Grants No. FPA2011-27853- 01 and No. FIS2008-01323.We assess the two-photon exchange contribution to the Lamb shift in muonic hydrogen with forward dispersion relations. The subtraction constant (T) over bar (0, Q(2)) that is necessary for a dispersive evaluation of the forward doubly virtual Compton amplitude, through a finite energy sum rule, is related to the fixed J = 0 pole generalized to the case of virtual photons. We evaluated this sum rule using excellent virtual photoabsorption data that are available. We find that the "proton polarizability correction" to the Lamb shift in muonic hydrogen is -(40 +/- 5) mu eV. We conclude that nucleon structure-dependent uncertainty by itself is unlikely to resolve the large (300 mu eV) discrepancy between direct measurement of the Lamb shift in mu H and expectations based on conventional hydrogen measurements.engjournal articlehttp://dx.doi.org/10.1103/PhysRevA.87.052501http://pra.aps.orgopen access53Compton-ScatteringProton StructureLow Q(2)AtomsFísica (Física)22 Física