Electromagnetic form factors: a window into the D c, D^* c, and D c^* molecular structure

Abstract The internal structure of exotic hadrons remains one of the most compelling puzzles in strong interaction physics. In this work, we provide crucial insights into the nature of doubly-charmed pentaquarks by investigating their electromagnetic properties. Using QCD light-cone sum rules, we present the first comprehensive calculation of the magnetic dipole moments of D c D Λ c, D^* c D ∗ Λ c, and D c^* D Λ c ∗ molecular pentaquarks with JP = 12^- J P = 1 2 -, 32^- 3 2 -, and 32^- 3 2 -, respectively. Our analysis reveals a striking hierarchy of magnetic moments: ₃ ₂^*> ₃^* ₂ > ₃ ₂ μ D Λ c ∗ > μ D ∗ Λ c > μ D Λ c, driven by distinct quark-level mechanisms. While light quarks dominate the overall response, we find that charm quark contributions become strategically important when light quark contributions partially cancel. Beyond dipole moments, we predict higher multipoles–electric quadrupole and magnetic octupole moments–for the spin-3/2 D^* c D ∗ Λ c and D c^* D Λ c ∗ states, which fingerprint the spatial deformation of these configurations, revealing prolate versus oblate charge distributions. These results provide the first systematic predictions for electromagnetic moments of molecular pentaquark configurations, establishing essential benchmarks for future theoretical and experimental studies. By systematically comparing our predictions with both compact doubly-charmed and hidden-charm pentaquark configurations, we establish robust benchmarks that discriminate between competing structural models, ultimately resolving the nature of doubly-charmed exotic hadrons.