Ionization energy losses of fast charged particles produced in matter

Abstract

1. Ionization energy losses of clusters formed by fast charged particles occurring at small distances from one another may differ significantly from the total ionization energy losses of the individual particles constituting the cluster if these particles are far from one another. This distinction is associated with the interference of the electromagnetic fields created by the particles of the cluster at distances that contribute significantly to ionization energy losses. Such a situation emerges, for example, when a high-energy electron‐ positron pair is produced in matter [1]. The point is that the characteristic angles of divergence of a high-energy pair produced in matter are very small. It follows that, over rather long a time interval, the transverse distance between the particles of the pair will be small in relation to the maximum impact-parameter values of ρ max ~ v / ω p , ( v is the particle velocity, and ω p is the plasmon frequency) that contribute significantly to the ionization energy losses of the individual particles of the pair. The electromagnetic fields of the electron and the positron of the product pair compensate each other partly at distances of v / ω p the from the pair in the transverse direction; therefore, the ionization energy losses of such a cluster are smaller than the ionization energy losses of the individual particles. By way of example, we indicate that, at photon energies of " ω ~ 100 GeV, characteristic angles of divergence of the particles forming the pair are