Number of events (or collisions) in an accelerator : N

Two proton beams are traveling in opposite directions in an accelerator. Each proton beam has a flux (L) of ~100 million protons/unit area/sec. How many events (proton-proton collisions) can we expect if both beams have fluxes of L1 and L2. For the sake of simplicity we let L1 = L2 = ~100 million protons/unit area/sec.