NIST Authors in **Bold**

Author(s): | Lawrence T. Hudson; C T. Chantler; M N. Kinnane; John D. Gillaspy; A.T. Payne; L F. Smale; Albert Henins; Joshua M. Pomeroy; J A. Kimpton; E Takacs; K Makonyi; |
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Title: | Reply to ,Comment on "Testing Three-body Quantum Electrodynamics with Trapped Ti20+ Ions: Evidence for a Z-Dependent Divergence between Experiment and Calculation" |

Published: | April 12, 2013 |

Abstract: | We find that Epp‰s [1] hypothesis - namely that the current experimental data set is well represented by a small constant or zero offset from the predictions of Artemyev et al. [2] - is not supported by standard statistical analysis. We find that adding the new datum recommended by Epp makes the discrepancy that we reported earlier grow with Z even more strongly - rather than weakly, as Epp suggests. Our primary conclusion [3] of an apparent Z-dependent discrepancy between experiment and theory is unchanged, and is qualitatively novel com- pared to earlier discussion of discrepancies in QED. While Epp suggests that our results extrapolate to problems at very high-Z, we note that our present and previous datasets both include data up to and including Z = 92, and the reduced chi-squared χ2r values showed a negligible discrepancy of the fit over this range of Z. [1] S. W. Epp, Phys. Rev. Lett. (2013). [2] A. N. Artemyev, V. M. Shabaev, V. A. Yerokhin, G. Plunien, and G. Soff, Phys Rev A 71, 062104 (2005). [3] C. T. Chantler, M. N. Kinnane, J. D. Gillaspy, L. T. Hudson, A. T. Payne, L. F. Smale, A. Henins, J. M. Pomeroy, J. N. Tan, J. A. Kimpton, et al., Phys Rev Letts 109, 153001 (2012). |

Citation: | Physical Review Letters |

Issue: | 159302 |

Pages: | pp. 159302-1 - 159302-2 |

Keywords: | x-ray spectroscopy, quantum electrodynamics |

Research Areas: | Radiation Physics |