Erlangen 2026 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 30: Hadron Structure and Spectroscopy VI

HK 30.1: Group Report

Thursday, March 19, 2026, 13:45–14:15, PHIL A 401

Inclusive measurement of R — Thomas Lenz, •Weiping Wang, and Achim Denig for the BESIII collaboration — Johannes Gutenberg-Universität Mainz, Germany

The inclusive measurement of R, which is the ratio of the leading-order cross sections between inclusive hadronic events and a pair of muon leptons, is of great importance in the precision test of the Standard Model. For example, the determination of quantum electrodynamics running coupling constant at the Z pole, the evaluation of the anoma- lous magnetic moment of muon, and search and study of exotic hadron states. In this presentation, we will introduce the inclusive measure- ment of R at BESIII, including the published results and ongoing ef- forts based on the conventional energy-scan method. In addition, we will present a novel approach for R measurement that combines the advantages of the initial-state radiation technique with the inclusive method. This approach enables an inclusive determination of R over the energy range from 0.3 to 2.0 GeV, which is of significant interest to the community.

Keywords: R value; inclusive measurement; Initial-State-Radiation technique; Standard Model