Evidence for Q-Dependent Nuclear Transverse-Momentum Redistribution Beyond Broadening from AI-driven analysis of p-Cu Drell-Yan

We extract a target-side Cu transverse-momentum profile from fixed-target $p$–Cu Drell–Yan data by holding a momentum-space proton reference fixed and training only an asymmetric Cu kernel in the small-$q_T$ region. In the supported window, $0.15\le x_{Cu}\le 0.46$ and $7.5\le Q_M\le 15.75$ GeV, the nuclear modification is not a universal width increase. It appears as $Q$-dependent redistribution: an $\mathcal{O}(1\mathrm{G}\mathrm{e}\mathrm{V})$ shoulder and compensating probability flow between shoulder and resolved-tail regions, beyond one-parameter broadening.