WIDG Seminar: Robert Perry, University of Adelaide, "Hadron Electromagnetic Form Factors"

Friday Dec 7, 2018, 1:00 PM → 2:00 PM US/Eastern

WL 216

Electromagnetic form factors give Lorentz invariant information about the electromagnetic charge distributions inside hadrons. They are thus a key probe of the dynamics of QCD in the low energy, non-perturbative regime. Importantly, it is well known that due to its characteristically light mass, the pion plays an important role in these observables. In the first part of this talk, I will discuss the implementation of pion loop corrections at the hadron level. I will show results for electromagnetic form factors calculated in the NJL Model and show that we see an improvement in the predicted Hyperon Magnetic moment when the pion loop effects are implemented in this way. One important input into this calculation is the pion form factor itself. Modern extractions of the pion form factor for moderate values of the photon virtuality (above about 0.3 GeV^2) arise from a model dependent extraction from pion electro-production data. In the second half of the talk, I will describe a simple model of pion electro-production, and examine the model dependence of the extraction method. I will show that in the context of this simple model, the extracted pion form factor is systematically overestimated.