Electric and magnetic timelike form factors of hyperons at large transfer momentum

TL;DR

This paper extends a covariant quark model to the timelike region to predict hyperon form factors at high momentum transfer, aligning well with recent experimental data and guiding future measurements.

Contribution

It applies a meson cloud-inclusive covariant quark model to timelike hyperon form factors without additional fitting, providing predictions for high $q^2$ regions.

Findings

Predictions agree with data for $q^2 > 15$ GeV$^2$ for several hyperons.

Model matches the ratio $|G_E/G_M|$ within current data limitations.

Upcoming data above $q^2=20$ GeV$^2$ can further test the model.

Abstract

There has been considerable progress in the study of the electromagnetic form factors of baryons in the timelike region, through electron-positron scattering reactions ($e^+ e^- \to B \bar B$), in the last two decades. Timelike experiments reveal information about the distribution of charge and magnetism inside the hyperons that cannot be obtained in spacelike experiments (electron scattering on baryons). Motivated by the novel data, we extend to the timelike region, without any further parameter fitting, a covariant quark model developed for the spacelike region that takes into account the meson cloud excitations of the baryon cores. We use the formalism to calculate the electric ($G_E$) and magnetic ($G_M$) form factors of spin 1/2 baryons in the large square transfer momentum $q^2$ region. Our calculations are compared with the available data from CLEO and BESIII above $q^2=10$ GeV$^2$. We conclude that our predictions for the effective form factors (combination between $G_E$ and $G_M$) are in good agreement with the $q^2 > 15$ GeV$^2$ data for $\Lambda$, $\Sigma^+$, $\Sigma^0$, $\Xi^-$ and $\Xi^0$. Upcoming data for $\Sigma^-$ can be used to further test our predictions. We also compare our model calculations with the available data for ratio $|G_E/G_M|$. We conclude that the present $q^2$ data range is not large enough to test our calculations, but that a more definitive test can be performed by upcoming data above $q^2=20$ GeV$^2$.