6533b851fe1ef96bd12a9721

RESEARCH PRODUCT

Nucleon andΔ(1232)form factors at low momentum transfer and small pion masses

subject

description

An expansion of the electromagnetic form factors of the nucleon and $\ensuremath{\Delta}(1232)$ in small momentum transfer and pion mass is performed in a manifestly covariant EFT framework consistent with chiral symmetry and analyticity. We present the expressions for the nucleon and $\ensuremath{\Delta}(1232)$ electromagnetic form factors, charge radii, and electromagnetic moments in the framework of $SU(2)$ baryon chiral perturbation theory, with nucleon and $\ensuremath{\Delta}$-isobar degrees of freedom, to next-to-leading order. Motivated by the results for the proton electric radius obtained from the muonic-hydrogen atom and electron-scattering process, we extract values for the second derivative of the electric form factor which is a genuine prediction of the ${p}^{3}$ $\mathrm{B}\ensuremath{\chi}\mathrm{PT}$. The chiral behavior of radii and moments is studied and compared to that obtained in the heavy-baryon framework and lattice QCD. The chiral behavior of $\ensuremath{\Delta}(1232)$-isobar properties exhibits cusps and singularities at the threshold of $\ensuremath{\Delta}\ensuremath{\rightarrow}\ensuremath{\pi}N$ decay, and their physical significance is discussed.