Electromagnetic form factors: A window into the $DΛ_c$, $D^*Λ_c$, and $DΛ_c^*$ molecular structure
U. Özdem
TL;DR
This work uses QCD light-cone sum rules to study the electromagnetic structure of doubly-charmed pentaquarks interpreted as molecular states $D\Lambda_c$, $D^*\Lambda_c$, and $D\Lambda_c^*$ with $J^P$ values $1/2^-$, $3/2^-$, and $3/2^-$, respectively. By constructing two-point correlation functions in an external EM field and matching the hadronic and QCD representations through a dispersion relation and Borel transformation, the authors extract magnetic dipole moments from zero-momentum-transfer form factors and predict higher multipoles via photon distribution amplitudes. The results reveal a clear hierarchy in magnetic moments with all three states negative and of sizable magnitude, dominated by light-quark contributions while charm quarks play a non-negligible role when cancellations occur; the predicted quadrupole and octupole moments indicate distinct prolate or oblate deformations tied to the underlying quark dynamics. These predictions provide essential benchmarks for differentiating molecular from compact multiquark pictures and offer guidance for future experimental studies of radiative transitions in these exotic states.
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 $DΛ_c$, $D^*Λ_c$, and $DΛ_c^*$ molecular pentaquarks with $J^P = \frac{1}{2}^-$, $\frac{3}{2}^-$, and $\frac{3}{2}^-$, respectively. Our analysis reveals a striking hierarchy of magnetic moments: $μ_{DΛ_c^*} > μ_{D^*Λ_c} > μ_{DΛ_c}$, 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 -- that fingerprint the spatial deformation of these states, 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. The distinctive patterns we uncover will enable quantitative comparisons with alternative structural models, ultimately helping to resolve the nature of doubly-charmed exotic hadrons.