Tensor-polarized parton density in the $N \rightarrow \Delta$ transition

The generalized parton distributions for transitions between baryon states with different masses have a forward limit in which they behave as parton densities (light-front momentum transfer $\Delta^+, \Delta_T = 0$, energy transfer $\Delta^- \neq 0$). These "transition parton densities'' can realize spin/isospin quantum numbers not accessible in the ground-state nucleon. The $N \rightarrow \Delta$ transition gives rise to a new parton density proportional to the $1/2 \rightarrow 3/2$ spin transition tensor. Its properties are derived, and its magnitude is estimated in the chiral quark-soliton model based on the large-$N_c$ limit of QCD.