# The muon g-2: the hadronic vacuum polarisation contributions

Keshavarzi, A
(2018) The muon g-2: the hadronic vacuum polarisation contributions. PhD thesis, University of Liverpool.

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## Abstract

The anomalous magnetic moment of the muon stands as an enduring test of the Standard Model (SM), where the 3:5 (or higher) discrepancy between the experimental measurement and the SM prediction could be an indication of the existence of new physics beyond the SM. This work presents a complete re-evaluation of the hadronic vacuum polarisation contributions to the anomalous magnetic moment of the muon from a combination of available electron-positron to hadrons cross section data as input in a predominantly data driven analysis. Focus has been placed on the development of a new data combination method, that has been advocated to be free of bias and allows for the full use of any available correlated statistical and systematic uncertainties into the determination of both the resulting mean value and corresponding error. In a related work, the three precision measurements of the two-pion cross section using initial state radiation by the KLOE collaboration provide an important input for the prediction of the hadronic contribution to the anomalous magnetic moment of the muon. These measurements are correlated for both statistical and systematic uncertainties and, therefore, the simultaneous use of these measurements requires covariance matrices that fully describe the correlations. The construction of these matrices has allowed for the determination of a combined KLOE measurement of the two-pion cross section. For the full calculation of the leading order and next-to-leading order hadronic vacuum polarisation contributions, all available electron-positron to hadrons cross section data have been analysed and included, where the new data compilation has yielded the full hadronic R-ratio and its covariance matrix from threshold to 11.2 GeV. Using these combined data and pQCD above that range results in estimates of the hadronic vacuum polarisation contributions to g-2 of the muon that yields a new determination for the SM prediction which is 3.7 standard deviations below the current experimental measurement. Detailed comparisons with results from similar related works are given, as well as discussions of the prospects for improving the calculation of these contributions in the future.

Item Type: Thesis (PhD) Fac of Science & Engineering > School of Mathematics Symplectic Admin 20 Nov 2018 16:36 03 Mar 2021 10:04 10.17638/03023290 Teubner, Thomas ORCID: 0000-0002-0680-0776 https://livrepository.liverpool.ac.uk/id/eprint/3023290