Lucas Platter

We study two-body scattering observables from real-time evolution in a finite periodic box. The system consists of two distinguishable particles on a two-dimensional lattice interacting through pointlike s - and p -wave interactions. We evolve their wave packets in real time, define detector observables through angular wedges in the relative coordinate, and attach infinite-volume labels obtained from the bound-state pole equation and the low-energy scattering amplitude. We train a convolutional neural network on this data and test its performance on previously unseen finite volume scattering data and find that is able to predict the total magnitude and angular shape of cross sections for previously unseen Hamiltonians.

We consider two-neutron halo nuclei in which the neutron core subsystem displays a resonance close to threshold. Such resonances can be generated in an effective field theory in which the scattering length and effective range are summed to all orders. We show that no three-body parameter is required to make predictions in this case and map out the universal features of such systems. We furthermore study the dependence of these universal features on the core mass. We apply our framework to the two-neutron halo nucleus ${}^{22}$C.

We make order-by-order predictions of neutron-deuteron total cross sections up to next-to-next-to-leading order in pionless effective field theory. Using Bayesian methods, we infer a posterior distribution for the breakdown scale. The result shows a mode near 100 MeV, and a combined analysis with neutron-proton scattering further sharpens the inference, placing the mode close to the pion mass scale, consistent with the expected range of pionless effective field theory.