Beam Fragmentation in Heavy Ion Collisions and its implication for RHIC triggers at low s

We show that with a realistic treatment of spectator momentum distributions the RHIC detector trigger sensitivity is high even when RHIC is run below injection energies. In particular, a problem region with $\sqrt{s_{NN}}$=10 to 60 or 80 GeV assuming a simple Fermi step model is not found when using a more realistic one. We argue also that production of fast nucleons (with momenta $> p_F$ in the nucleus rest frame) provides complementary information about the collision process.