Conveners
Session 2
- Shuangshi Fang (IHEP)
The improvement of the standard model (SM) prediction of the muon anomalous magnetic moment $(g-2)$ is of utmost importance in view of the recent and upcoming experimental results from the FNAL E989 experiment. The BESIII collaboration is strongly involved in providing valuable inputs towards a strong reduction of the dominant sources of uncertainty to the SM calculation: the hadronic vacuum...
We report studies of hadrons performed using two-photon processes at Belle. In particular, the two-photon process $\gamma\gamma \to \gamma\psi(2S)$ is studied for the first time in an effective center-of-mass energy ranging from 3.7 to 4.2 GeV. Evidence is established for a structure in the $\gamma\psi(2S)$ invariant-mass distribution around 3920 MeV/$c^{2}$, and hint is found for another...
We present a parameter-free prediction of the two-photon transitions of the charmonium system $[c\bar c] \to \gamma^*\gamma$ in a relativistic light-front formalism. The use of light-front formulation automatically takes into account the large-$Q^2$ behavior of the process as predicted by pQCD. Furthermore, the relativistic nature of the light-front dynamics provides a reliable access to the...
We accomplish the complete two-loop computation of the leading-twist contribution to the photon-pion transition form factor $\gamma \gamma^∗ \to \pi $ by applying the hard-collinear factorization theorem together with modern multi-loop techniques. The resulting predictions for the form factor indicate that the two-loop perturbative correction is numerically important. We also demonstrate that...
