Dresden 2013 – scientific programme
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HK: Fachverband Physik der Hadronen und Kerne
HK 61: Hadronenstruktur und -spektroskopie
HK 61.5: Talk
Thursday, March 7, 2013, 15:15–15:30, HSZ-105
Study of the transition form factors in the γ γ* interaction processes e+e− h (h = π0 / η) at BES III — •Elisabetta Prencipe and Achim Denig — Institute for Nuclear Physics, Johannes Gutenberg-Universität Mainz
The experiment BES III, located at BEPC2 in Beijing (China) is a symmetric e+e− collider well suited for spectroscopy studies. It offers also a unique opportunity to perform precision measurements of the transition form factors as function of the transfer momentum Q2 at low energy. This is important to our better understanding of the Standard Model prediction of the muon anomaly aµ, in particular of the light-by-light hadronic contribution, as the study of the form factor at medium and low Q2 range represents a test of the Standard Model at low energy frontiers. The study of the channels e+e− π0/ η via γ γ* interactions (in the space-like Q2 region), where both π0 and η in this analysis decay to 2-photons, plays an important role in this context. First results with the BES III dataset collected at the energy in the center of mass of ψ″(3770) will be shown here, corresponding to an integrated luminosity of 2.9 fb−1, in the range of Q2 ∈ [0.3;10.0] GeV2. This analysis allows to test with high precision the distribution of the function F(Q2)·Q2 in the range of Q2 ∈ [0.3;1.5] GeV2; to improve the previous measurements performed by CLEO in the range of Q2 ∈ [1.5;3.0] GeV2; to cross check the BaBar and Belle data in the range of Q2 ∈ [4.0;10.0] GeV2.