Speaker
Description
The tensor form factors of the nucleon carry essential information for understanding its internal spin structure. The monopole tensor form factor at $Q^2=0$ is identified as the nucleon tensor charge, which corresponds to the first moment of the leading-twist transversity distribution $h_1(x)$. While transversity has been studied extensively both in theory and in experiment, the other tensor form factors have attracted far less attention. In this talk, we present recent results for the nucleon multipole tensor form factors obtained within the pion mean-field theory. The framework rests on the effective dynamics arising from spontaneous chiral symmetry breaking and on the mean-field description of the nucleon at leading order in the large-$N_c$ limit. We find that the tensor charge ($g_{T}^{u-d}=0.99$) and the tensor anomalous magnetic moment ($\kappa_{T}^{u+d}=7.61$) are dominated by valence quark contributions, whereas the tensor quadrupole moment ($Q_{T}^{u-d}=-7.02$) exhibits significant sea quark effects. We also explore how these moments depend on the soliton size and the pion mass, observing a smooth transition between the non-relativistic and relativistic regimes. The results agree well with available lattice QCD data and provide predictions for quantities that have not yet been measured.
