We present benchmark calculations of Zemach moments and radii of H2,3 and He3,4 using various few-body methods. Zemach moments are required to interpret muonic atom data measured by the CREMA collaboration at the Paul Scherrer Institute. Conversely, radii extracted from spectroscopic measurements can be compared with ab initio computations, posing stringent constraints on the nuclear model. For a given few-body method, different numerical procedures can be applied to compute these quantities. A detailed analysis of the numerical uncertainties entering the total theoretical error is presented. Uncertainties from the few-body method and the calculational procedure are found to be smaller than the dependencies on the dynamical modeling and the single nucleon inputs, which are found to be 2%. When relativistic corrections and two-body currents are accounted for, the calculated moments and radii are in very good agreement with the available experimental data.
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S.P. and M.P. would like to thank Rocco Schiavilla and Laura Elisa Marcucci for useful discussions, and gratefully acknowledge the computing resources of the high-performance computing cluster operated by the Laboratory Computing Resource Center (LCRC) at Argonne National Laboratory (ANL). This work was supported in parts by the Natural Sciences and Engineering Research Council (NSERC), the National Research Council of Canada, by the Deutsche Forschungsgemeinschaft DFG through the Collaborative Research Center. [The Low-Energy Frontier of the Standard Model (SFB 1044)], and through the Cluster of Excellence [Precision Physics, Fundamental Interactions and Structure of Matter (PRISMA)]. The work of R.B.W. is supported by the US Department of Energy, Office of Science, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357.
© 2019 American Physical Society.