Leading-order hadronic contribution to the electron and muong− 2
Fred Jegerlehner · EPJ Web of Conferences · 2016
I present a new data driven update of the hadronic vacuum polarization effects for the muon and the electron g − 2. For the leading order contributions I find aμhad(1) = (688.57 ± 4.28) [688.91 ± 3.52] × 10−10 based on e+e− data [incl. τ data], aμhad(2) = (− 9.92 ± 0.10) × 10−10 (NLO) and aμhad(3) = (1.23 ± 0.01) × 10−10 (NNLO) for the muon, and aehad(1) = (185.11 ± 1.24) × 10−14 (LO), aehad(2) = (−22.15 ± 0.16) × 10−14 (NLO) and aehad(3) = (−2.80 ± 0.02) × 10−14 (NNLO) for the electron. A problem with vacuum polarization undressing of cross-sections (time-like region) is addressed. I also add a comment on properly including axial mesons in the hadronic light-by-light scattering contribution. My estimate here reads aμ[a1, f′1, f1] ∼ (7.51 ± 2.71) × 10−11. With these updates aμexp – aμthe = (31.0 ± 8.2) × 10−10 a 3.8σ deviation, while aeexp – aethe = (−1.14 ± 08.2) × 10−12 shows no significat deviation.