Production of Massive Stable Particles in Inflaton Decay

We point out that inflaton decays can be a copious source of stable or long-lived particles chi with mass exceeding the reheat temperature T(R) but less than half the inflaton mass. Once higher order processes are included, this statement is true for any chi particle with renormalizable (gauge or Yukawa) interactions. This contribution to the chi density often exceeds the contribution from thermal chi production, leading to significantly stronger constraints on model parameters than those resulting from thermal chi production alone, particularly in models containing stable charged particles.