arXiv subjects

M. Nio

Publications and source records attributed to M. Nio.

24 records · Page 2Linked to original sources

arXiv2002

Revised $α^4$ term of lepton $g-2$ from the Feynman diagrams containing an internal light-by-light scattering subdiagram

The $α^4$ contribution to the lepton $g-2$ from a gauge-invariant set of 18 Feynman diagrams containing a light-by-light scattering subdiagram internally has been reevaluated by a method independent of the previous approach. Comparison of two methods revealed a program error in the first version. Correcting this error, the contributions of these 18 diagrams become -0.990 72 (10)$(α/π)^4$ and -4.432 43 (58)$(α/π)^4$ for the electron and muon $g-2$, respectively. The correction is not large enough to affect the comparison between theory and experiment for the muon $g-2$, but it does alter the inferred value for the fine structure constant $α^{-1}$ by 6 ppb.

hep-ph↗

arXiv1999

Accuracy of Calculations Involving $α^3$ Vacuum-Polarization Diagrams: Muonic Hydrogen Lamb Shift and Muon $g-2$

The contribution of the $α^3$ single electron-loop vacuum-polarization diagrams to the Lamb shift of the muonic hydrogen has been evaluated recently by two independent methods. One uses the exact parametric representation of the vacuum-polarization function while the other relies on the Padé approximation method. High precision of these values offers an opportunity to examine the reliability of the Monte-Carlo integration as well as that of the Padé method. Our examination covers both muonic hydrogen atom and muon $g-2$. We tested them further for the cases involving two-loop vacuum polarization, where an exact analytic result is known. Our analysis justifies the result for the Lamb shift of the muonic hydrogen and also resolves the long-standing discrepancy between two previous evaluations of the muon $g-2$ value.

hep-ph↗

arXiv1999

Sixth-Order Vacuum-Polarization Contribution to the Lamb Shift of the Muonic Hydrogen

The sixth-order electron-loop vacuum-polarization contribution to the $2P_{1/2} - 2S_{1/2}$ Lamb shift of the muonic hydrogen ($μ^{-} p^+$ bound state) has been evaluated numerically. Our result is 0.007608(1) meV. This eliminates the largest uncertainty in the theoretical calculation. Combined with the proposed precision measurement of the Lamb shift it will lead to a very precise determination of the proton charge radius.

hep-ph↗

arXiv1997

Radiative Corrections to the Muonium Hyperfine Structure. II. The $α(Zα)^2 $ Correction

This is the second of a series of papers on the radiative corrections of order $α^2 (Zα)$, $α(Zα)^2$, and various logarithmic terms of order $α^4$, to the hyperfine structure of the muonium ground state. This paper deals with the $α(Zα)^2$ correction. Based on the NRQED bound state theory, we isolated the term of order $α(Zα)^2$ exactly. Our result $+16.904 2 (11) α(Zα)^2 E_F / π$ for the non-logarithmic part is consistent with the $α(Zα)^2$ part of Sapirstein's calculation and the recent result of Pachucki, and reduces the numerical uncertainty in the $α(Zα)^2$ term by two orders of magnitude.

hep-ph↗

arXiv1996

Radiative Corrections to the Muonium Hyperfine Structure. I. The $α^2 (Zα)$ Correction

This is the first of a series of papers on a systematic application of the NRQED bound state theory of Caswell and Lepage to higher-order radiative corrections to the hyperfine structure of the muonium ground state. This paper describes the calculation of the $α^2 (Zα)$ radiative correction. Our result for the complete $α^2 (Zα)$ correction is 0.424(4) kHz, which reduces the theoretical uncertainty significantly. The remaining uncertainty is dominated by that of the numerical evaluation of the nonlogarithmic part of the $α(Zα)^2$ term and logarithmic terms of order $α^4$.

hep-ph↗

arXiv1994

Improved Theory of the Muonium Hyperfine Structure

Terms contributing to the hyperfine structure of the muonium ground state at the level of few tenths of kHz have been evaluated. The $α^2 (Zα)$ radiative correction has been calculated numerically to the precision of 0.02 kHz. Leading $\ln (Zα)$ terms of order $α^{4-n} (Zα)^n , n=1,2,3,$ and some relativistic corrections have been evaluated analytically. The theoretical uncertainty is now reduced to 0.17 kHz. At present, however, it is not possible to test QED to this precision because of the 1.34 kHz uncertainty due to the muon mass.

hep-ph↗