Muon g -2 and Δ α connection
Abstract
The discrepancy between the Standard Model theory and experimental measurement of the muon magnetic moment anomaly, aμ=(gμ-2 ) /2 , is connected to precision electroweak (EW) predictions via their common dependence on hadronic vacuum polarization effects. The same data for the total e+e-→hadrons cross section, σhad(s ), are used as input into dispersion relations to estimate the hadronic vacuum polarization contributions, aμhad,VP, as well as the five-flavor hadronic contribution to the running QED coupling at the Z -pole, Δ αhad(5 )(MZ2), which enters natural relations and global EW fits. The EW fit prediction of Δ αhad(5 )(MZ2)=0.02722 (41 ) agrees well with Δ αhad(5 )(MZ2)=0.02761 (11 ) obtained from the dispersion relation approach, but exhibits a smaller central value suggestive of a larger discrepancy Δ aμ=aμexp-aμSM than currently expected. Postulating that the Δ aμ difference may be due to unforeseen missing σhad(s ) contributions, implications for MW, sin2θefflep and MH obtained from global EW fits are investigated. Shifts in σhad(s ) needed to bridge Δ aμ are found to be excluded above √{s }≳0.7 GeV at the 95% C.L. Moreover, prospects for Δ aμ originating below that energy are deemed improbable given the required increases in the hadronic cross section. Such hypothetical changes to the hadronic data are also found to affect other related observables, such as the electron anomaly, aeSM, the rescaled ratio Re /μ=(mμ/me)2(aehad,LO VP/aμhad,LO VP) , and the running of the weak mixing angle at low energies, although the consequences of these are currently less constraining.
- Publication:
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Physical Review D
- Pub Date:
- August 2020
- DOI:
- 10.1103/PhysRevD.102.033002
- arXiv:
- arXiv:2006.12666
- Bibcode:
- 2020PhRvD.102c3002K
- Keywords:
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- High Energy Physics - Phenomenology;
- High Energy Physics - Experiment
- E-Print:
- 33 pages, 16 figures