Speaker
Description
In recent years, there was significant progress in the experimental study of the electromagnetic structure of baryons in the timelike region through electron-positron scattering reactions with the creation of baryon-antibaryon pairs: $e^+ e^- \to B \bar B^\prime$. From the annihilation cross sections, we can determine the electromagnetic form factors of baryons in terms of the square transfer momentum, $q^2$, obtaining information that is not available in electron scattering reactions (spacelike region). Aiming for the interpretation of the new data for the electromagnetic form factors of hyperons above $q^2= 10$ GeV$^2$, we extend a quark model, developed previously to the spacelike region ($q^2 < 0$), to the large $q^2$ region, using asymptotic relations. Our model calculations compare well with the available data from BESIII for the effective form factors of hyperons of the baryon octet ($\Lambda$, $\Sigma$, and $\Xi$) above $q^2 = 15$ GeV$^2$. Preliminary calculations suggest that we can also provide reliable predictions for the ratio between the electric and magnetic form factors ($R= G_E/G_M$) above $q^2=20$ GeV$^2$. Our model predictions may be tested in the near future at BESIII, when measurements of the electric ($G_E$) and magnetic ($G_M$) form factors and the relative phase between the form factors become available for the range $q^2 > 20$ GeV$^2$. We also discuss the extension of our formalism for transitions between baryon octet and baryon decuplet and other annihilation reactions.