Implications of Efimov physics for the description of three and four nucleons in chiral effective field theory

Understand

In chiral effective field theory the leading order (LO) nucleon-nucleon potential includes two contact terms, in the two spin channels $S=0,1$, and the one-pion-exchange potential.

• When the pion degrees of freedom are integrated out, as in the pionless effective field theory, the LO potential includes two contact terms only.
• In the three-nucleon system, the pionless theory includes a three-nucleon contact term interaction at LO whereas the chiral effective theory does not.
• Accordingly arbitrary differences could be observed in the LO description of three- and four-nucleon binding energies.