Nuclear Fragmentation at the Future Electron-Ion Collider

TL;DR

Problem addressed: quantify low-energy nuclear fragmentation induced by electromagnetic interactions and contrast the EIC with LHC UPC environments. Methods: represent IVGDR, ISGQR and IVGQR with Lorentians and compute $\sigma_x(\omega) = b_x(\omega) \sum_{GR} \sigma_\gamma^{GR}(\omega)$ using $b_x(\omega) = \Gamma_x(\omega^*)/\Gamma_{tot}(\omega^*)$, with $E_{lab} \approx 89$ GeV at the EIC and $\sqrt{s_{NN}} = 5.5$ TeV at the LHC. Findings: cross sections at the LHC exceed those at the EIC by about three orders of magnitude; ${}^{238}$U fragmentation at the LHC shows a double-humped fission signature near A ~ 100 and A ~ 140, while neutron evaporation dominates at the EIC; pomeron exchange is absent at the EIC, highlighting a clean EM probe of low-excitation nuclear dynamics. Conclusions: UPCs remain favorable for detailed nuclear-structure studies, whereas the EIC provides a clean electromagnetic probe of low-excitation dynamics, yielding complementary information and informing plans to explore potentially new nuclei under different excitation conditions.

Abstract

We investigate aspects of low-energy nuclear reactions that could be explored at the forthcoming Electron-Ion Collider (EIC) at Brookhaven National Laboratory and compare them with analogous measurements performed in ultraperipheral collisions (UPCs) at the Large Hadron Collider (LHC) at CERN. The estimated fragmentation cross sections at the EIC are roughly three orders of magnitude smaller than those observed at the LHC. At the LHC, uranium nucleus fragmentation exhibits a distinctive double-peaked mass spectrum arising from fission processes, whereas at the EIC, the breakup pattern is mainly characterized by neutron evaporation and a vastly reduced yield of fission fragments, about four orders of magnitude fewer events in comparison.