GEANT4 Software Library for Simulation of Particle Identification Processes

Vladimir Grichine


Summary (extended abstract)

     Relativistic particle energy loss in a medium can be subdivided to Cerenkov (CL) and Bohr (BL) losses, i.e. the works done by the particle against the transverse and longitudinal (relative to the wave vector) components of its electric field in the current particle position, respectively. In terms of quantum approach CL and BL are responsible for the generation of the transverse (photons in medium) and longitudinal (plasmons, delta-electrons) medium excitations along the particle trajectory, respectively.
     CL reflecting the contribution from the particle electric current is responsible for the relativistic (on the particle Lorentz factor or velocity) dependence of the particle energy loss. It results in observable effects that are used for charged particle identification, i.e. soft (non-destructive for the particle momentum) estimation of the particle Lorentz factor (or, in other words, its velocity). In the visible and ultraviolet ranges of transfered energies CL generalises Cerenkov radiation for the case, when the medium absorption is taken into account.
     In the range of atomic frequencies, where the generated photons are absorbed in the vicinity of the particle trajectory resulting in measured ionisation, CL describes the relativistic rise of dE/dx. In the X-ray range, where CL in uniform medium is suppresses by destructive interference, introduction of proper distributed medium interfaces recovers the generation of X-ray photons. The detection of these photons (X-ray transition radiation) allows to extend the relativistic dependence of the particle energy loss.
     Consideration of relativistic dependence of the particle energy loss is convenient from the simulation point of view allowing to track (involving
all background processes) secondary photons just from the points of their generation. GEANT4 Object-Oriented Toolkit for simulation in High Energy Physics provides extended tools for simulation of particle identification processes in complex detector geometries. Simulation results are in good agreement with experimental data.