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Muonic-hydrogen Lamb shift: dispersing the nucleon-excitation uncertainty with a finite-energy sum rule

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Llanes Estrada, Felipe José and Gorchtein, Mikhail and Szczepaniak, Adam P (2013) Muonic-hydrogen Lamb shift: dispersing the nucleon-excitation uncertainty with a finite-energy sum rule. Physical Review A, 87 (5). ISSN 1050-2947

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Official URL: http://dx.doi.org/10.1103/PhysRevA.87.052501


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Abstract

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.


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© 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.

Uncontrolled Keywords:Compton-Scattering, Proton Structure, Low Q(2), Atoms
Subjects:Sciences > Physics
ID Code:23577
Deposited On:21 Nov 2013 13:02
Last Modified:20 Apr 2018 18:08

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