Erlangen 2026 – scientific programme

Parts | Days | Selection | Search | Updates | Downloads | Help

HK: Fachverband Physik der Hadronen und Kerne

HK 30: Hadron Structure and Spectroscopy VI

HK 30.2: Group Report

Thursday, March 19, 2026, 14:15–14:45, PHIL A 401

Experimental input to HVP from the BESIII collaboration — •Riccardo Aliberti, Achim Denig, Christoph Redmer, and Weiping Wang for the BESIII collaboration — JGU Mainz

The time-like pion (vector) Form Factor (FF), i.e. the cross section for the process e⁺e⁻ → π⁺π⁻, is the most important input to the dispersive evaluation of the Hadronic Vacuum Polarization (HVP) contribution to the anomalous magnetic moment of the muon a_µ. Decades of pion FF, and in general hadronic cross section, measurements have allowed the muon g-2 theory initiative to publish in 2020 a SM prediction for a_µ with sub-percent accuracy on the HVP contribution. This value is in strong tension (more than 5σ) with the latest experimental results reported by the muon g-2 collaboration. Despite such a tension would be a clear sign of new Physics, recent ab-initio calculations of HVP from lattice QCD have reached an accuracy competitive with the dispersive approach and their results lead to a SM value for a_µ, which is well in agreement with the direct measurements. At the same time, a new measurement of the pion FF by the CMD-3 collaboration shows a systematical deviation from previous results which would cover the discrepancy between the dispersive evaluation of HVP and the results from lattice QCD. In this talk, we will present the experimental efforts on going within the BESIII collaboration to provide new inputs to the dispersive evaluation of HVP with particular emphasis on a new high-precision measurement of the pion FF.

Keywords: HVP, muon g-2, hadronic cross section