Impact parameter

As the impact parameter, the minimum distance of the focal points of the two particles is referred to in the physics of collisions of two particles, which would arise in the event that between the two particles, no force would act, so that the two particles would pass on linear trajectories. It is usually denoted by the letter b.

To the trajectory of a particle in a stationary force field which emanates from one point, the so-called scattering center, it denotes the minimum distance analogous to that point for the force-free case. To simplify the mathematical treatment of collisions of two particles, the action is usually considered from the center of mass system out. In this case, it can be the path of a single particle with the reduced mass to assign a stationary force field, said force depending on the distance is the same. The interparticle distance corresponds to the distance from the scattering center, so that the impact parameter remains the same in this analysis.