Unbinding the Deuteron

We consider a description of the deuteron based on meson exchange potentials. A key feature is the inclusion of the I=S=0 two-pion intermediate state ('sigma(600)') as a significant component of the inter-nucleon potential energy. In this approach, deuteron binding is seen to be predominantly a consequence of sigma(600) and omega(783) exchange, with a secondary tole played by rho(770). We explore sensitivity of two-nucleon binding to changes in the potential and thereby obtain an anthropic constraint -- that the deuteron unbinds for a modest decrease (about 6%) in the attractive sigma(600) potential.