The femtobarn is a unit of area. The inverse femtobarn is basically saying the number of interactions "per femtobarn". A higher value means more interactions are occurring.
When you fire a beam of particles at something, or another stream of particles then you usually want interactions to happen. Some particles miss, some interact and some are moving too past and fly right by. There is an optimum energy where the most particle interactions occur. If you plot out the interaction rates then you usually get a bell curve. This is known as the excitation function for that interaction.
When you fire a beam of particles at something, or another stream of particles then you usually want interactions to happen. Some particles miss, some interact and some are moving too past and fly right by. There is an optimum energy where the most particle interactions occur. If you plot out the interaction rates then you usually get a bell curve. This is known as the excitation function for that interaction.