Producing and Studying Rare Isotopes in $e+A$ Collisions at the Electron-Ion Collider

Abstract

The Electron--Ion Collider (EIC) offers a unique environment to study kinematically controlled lepton--nucleus (e+A) reactions, where a primary hard scattering is followed by an intranuclear cascade and the subsequent statistical de-excitation of the nuclear remnant. Utilizing the BeAGLE model, we demonstrate that event-by-event fluctuations in nucleon removal and energy deposition populate a diverse ensemble of excited remnants. Furthermore, we show that varying the target mass systematically shifts the distribution of these remnants across the (N, Z) plane. Although this excited prefragment remnant is not directly observable, its properties are shown to be strongly correlated with final-state fragments; specifically, the largest nuclear residue and the intensity of evaporation activity serve as effective experimental proxies for event-level remnant characterization. We also evaluate photon observables essential for nuclear spectroscopy. While various photon sources overlap significantly in pseudorapidity, we find that in the nucleus-rest frame, the low-energy spectrum is dominated by de-excitation $γ$ rays and exhibits distinct discrete structures. These findings motivate an EIC research program that correlates rare-isotope production and de-excitation radiation with well-defined initial conditions, providing a collider-based approach to nuclear spectroscopy that is complementary to existing fixed-target facilities.

Figures (8)

• Figure 1: Schematic illustration of the main reaction stages in electron–nucleus ($e+A$) collisions. A high-energy virtual photon initiates a hard scattering on a quark, followed by parton showering and hadronization, intranuclear cascade and pre-equilibrium dynamics, and finally nuclear de-excitation via particle evaporation and $\gamma$ emission from the excited residual nucleus.
• Figure 2: Chart of nuclides in the $(N, Z)$ plane. Black squares indicate stable isotopes defining the valley of stability. The green region represents experimentally observed isotopes, while the gray area illustrates the predicted range of bound nuclei extending out to the theoretical drip lines. The presented data are from Refs. NNDC_NuDatNeufcourt:2020nme.
• Figure 3: Event-by-event correlations between the number of neutrons and protons for (a) excited nuclear remnant and (b) the largest residual nucleus, from Case-1, for $e{+}\text{A}$ at $18 \times 110$ GeV with $\tau_f = 5$ fm/$c$. The gray area illustrates the predicted range of bound nuclei extending out to the theoretical drip lines Neufcourt:2020nme.
• Figure 4: Event-by-event correlations between the excited nuclear remnant ($A^{\ast}$) and the largest residual nucleus ($A^{\prime}$) panel (a) and the largest residual nucleus combined with the scaled evaporation neutron energy panel (b), from Case-1, for $e{+}\text{A}$ at $18 \times 110$ GeV with $\tau_f = 5$ fm/$c$.
• Figure 5: Inclusive photon kinematics from BeAGLE at $18 \times 110$ GeV, shows the pseudorapidity distribution for $e{+}{}^{238}\text{U}$, decomposed into photons from hard scattering, intranuclear cascades, and nuclear de-excitation.