Photon Interactions in Three-Nucleon Systems

Three-nucleon systems offer a relatively nontrivial system to test theories of nuclear interactions including with external currents. At "low energies" nuclear systems can be described using pionless effective field theory (EFT). Pionless EFT has the advantage of being model independent and allows for systematically improvable calculations with error estimates. This talk will discuss recent strictly perturbative pionless EFT calculations of cold neutron-deuteron capture and two-body triton photodisintegration. In addition this talk will demonstrate the utility of using Wigner-SU(4) spin-isospin symmetry to understand these interactions. I will argue that a dual expansion in pionless EFT and Wigner-SU(4) symmetry breaking serves as a more controlled EFT expansion for cold neutron-deuteron capture as opposed to pionless EFT alone.