Effects of theta on the deuteron binding energy and the triple-alpha process

We study the effects that a nonzero strong-CP-violating parameter θ would have on the deuteron and diproton binding energies and on the triple-alpha process. Both these systems exhibit fine-tuning, so it is plausible that a small change in the nuclear force would produce catastrophic consequences. Such a nuclear force is here understood in the framework of an effective Lagrangian for pions and nucleons, and the strength of the interaction varies with θ. We find that the effects are not too dramatic. © 2010 The American Physical Society.