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HIC for FAIR logo Nuclear Physics Colloquium

Venue: Physics Building, Max-von-Laue-Str. 1, Seminar Room PHYS 2.116
Time: Thursday, June 09, 4:30 pm (s.t.)
Contact: hees@fias.uni-frankfurt.de


Electromagnetic form factors - Why they are interesting and how to calculate them

Stefan Leupold (University Uppsala)

Modern hadron physics plays a vital role for two fundamental questions: 1. How do the known elementary particles form the matter around us? 2. Is there physics beyond the known elementary particles? Concerning the first question, hadron physics studies how the quarks and gluons form hadrons. Electromagnetic form factors encode an important part of this information. Concerning the second question, hadron physics is needed to provide reliable standard-model predictions for high-precision quantities like the magnetic moment of the muon. Only then a possible deviation between observation and standard-model prediction can point to the influence of new physics instead of to the influence of quantitatively not understood hadronic fluctuations. For the magnetic moment of the muon electromagnetic transition form factors of mesons play a decisive role to decrease the theoretical uncertainty of the standard-model prediction.

The major part of my talk will report about the ongoing work to calculate the pion transition form factor in a model independent way and therefore with a reliable estimate for the theoretical uncertainty. The final aim is to qualitatively and quantitatively improve the standard-model prediction for the gyromagnetic ratio of the muon.

The last part of my talk will address form factors of hyperons. These siblings of the nucleon will be copiously produced in proton-proton and proton-antiproton collisions at FAIR and can be studied by HADES and PANDA, respectively. The intrinsic structure of hyperons can be probed in dilepton decays. It will be interesting to see how much alike or different the intrinsic structure of hyperons is as compared to nucleons and Deltas.

On the technical side the presented calculations for both the pion and the hyperons are based on dispersion theory and chiral perturbation theory.


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