Mainz 2014 – scientific programme

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T: Fachverband Teilchenphysik

T 86: Elektroschwache Physik (Theorie) 1

T 86.6: Talk

Wednesday, March 26, 2014, 18:00–18:15, P103

Some four-loop corrections to the anomalous magnetic moment of the muon and the electron — •Alexander Kurz^1,2, Tao Liu¹, Peter Marquard², and Matthias Steinhauser¹ — ¹Institut für Theoretische Teilchenphysik, Karlsruhe — ²Deutsches Elektronen-Synchrotron, Zeuthen

The anomalous magnetic moment of the muon a_µ and the electron a_e are determined with high experimental precision which requires high-order perturbative calculations on the theory side. In this talk we present the perturbative four-loop QED contribution induced by closed heavy lepton loops. We exploit the strong hierarchy between the tau, muon and electron masses (m_τ≫ m_µ≫ m_e) and apply the method of asymptotic expansion. This leads to an analytic expansion in the inverse heavy lepton masses which converges rapidly. In case of a_µ the expansion parameter is given by the ratio of the muon and tau lepton mass whereas for a_e both the muon and tau lepton are considered as heavy. As a further ingredient to a_µ we discuss the hadronic contribution. Using a precise parametrization of the experimental result for the total hadronic cross section in electron positron annihilation in combination with methods based on asymptotic expansion we can confirm the leading and next-to-leading order hadronic corrections present in the literature. Furthermore, new next-to-next-to-leading order results are provided.