Speaker
Description
The hadronic vacuum polarization is an important contribution to the running QED coupling constant at the $Z$ pole, $\alpha_\mathrm{QED}(M_Z^2)$, and the anomalous magnetic moment of the muon $a_\mu = (g_\mu - 2) / 2$. Both quantities allow for precision tests of the Standard Model (SM). Their theoretical uncertainties are dominated by hadronic contributions. Experimental inputs, like the hadronic $R$ value, are used in dispersive approaches to calculate these quantities.
The large data sets collected at the BESIII experiment at the $e^+ e^-$ collider BEPCII in Beijing, China, offer an excellent environment for initial state radiation (ISR) measurements. This poster discusses the feasibility of using the ISR technique to measure $R_\mathrm{had}$ inclusively in a continuous spectrum compared to the established scan technique. This is crucial given the standing $5.1 \, \sigma$ discrepancy between the experimental world average of $a_\mu$ and the SM prediction of the Muon $g-2$ Theory Initiative and allows for an independent perspective on the existing tensions within hadronic cross section measurements in $e^+ e^-$ and between dispersive and Lattice QCD evaluations.
| Parallel Session | Poster Session |
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