N\to \Delta(1232) Transition Form Factors: Complementary Prospects with SoLID and ALERT

We present a complementary study to determine the $\gamma^\ast n\!\to\!\Delta(1232)$ transition form factors at Jefferson Lab using two distinct detector approaches.

\textbf{SoLID} (large acceptance, \SI{11}{GeV} beam) enables high-luminosity, fine-binned measurements of exclusive $(e,e'\pi N)$ cross sections in the $\Delta$ region ($W\!\approx\!1.20$--$1.26$~GeV) over broad $Q^2$ and full azimuth, allowing extractions of $\{\sigma_T,\sigma_L,\sigma_{LT},\sigma_{TT}\}$ and constrained multipole fits to $M1^+$, $E1^+$, and $S1^+$. From these, the ratios $\mathrm{EMR}=E2/M1$ and $\mathrm{CMR}=C2/M1$ versus $Q^2$ directly probe nucleon--$\Delta$ deformation and nonperturbative dynamics.

\textbf{ALERT} uses \SI{11}{GeV} electrons on a $^4$He target with recoil tagging to isolate quasi-free neutron kinematics. Large angular coverage ($\theta_e\approx5^\circ$--$45^\circ$ with comparable hadron coverage) and missing-mass exclusivity provide robust background rejection and control of nuclear effects.

Event generation and acceptance studies employ experiment-specific geometries with MAID-weighted kinematics in $(Q^2,W,\theta^\ast,\phi^\ast)$; radiative and nuclear-motion effects enter the systematic budget.

Together, SoLID’s statistics and coverage and ALERT’s clean neutron selection deliver precise, complementary constraints on the $N\!\to\!\Delta$ transition at intermediate $Q^2$. We will present kinematic reach, acceptance, and projected sensitivities.