2003/10/31 by Stephane Ghozzi, Stéphane Ghozzi, Fred Jegerlehner · 6 citations
Physics and Astronomy · #Form factor (electronics) #Hadron #High-Energy Particle Collisions Research #Isospin #Meson #Muon #Nuclear physics #Particle physics #Particle physics theoretical and experimental studies #Physics #Pion #Quantum Chromodynamics and Particle Interactions #Quantum mechanics #hep-ph
paper · pdf · doi:10.1016/j.physletb.2004.01.021
published as Phys.Lett.B583:222-230,2004 · 11 pages, Latex, 1 table, 3 figures; update: several points described in more detail, slightly shifted fit parameters (Tab.1), 3 citations added
arxiv created 2004/01/09 · openalex publication_date 2004/02/05 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We study possible so far unaccounted isospin breaking effects in the relation between the pion form factor as determined in e+e− experiments and the corresponding quantity obtained after accounting for known isospin breaking effects by an isospin rotation from the τ-decay spectra. In fact the observed 10% discrepancy in the respective pion form factors may be explained by the isospin breaking which is due to the difference between masses and widths of the charged and neutral ρ mesons. Since the hadronic contribution to the muon anomalous magnetic moment can be calculated directly in terms of the e+e−-data the corresponding evaluation seems to be more reliable. Our estimate is aμhad(1)=(694.8±8.6)×10−10. The τ-data are useful at the presently aimed level of accuracy only after appropriate input from theory.