NEST (Noble Element Simulation Technique) is an unprecedented comprehensive, accurate, and precise simulation of the excitation, ionization, and corresponding scintillation and electroluminescence processes in liquid noble elements, useful for direct dark matter detectors, double beta decay searches, PET scans, and general radiation detection technology. NEST has been verified as robust against a long list of past experimental results.

The latest version of NEST (Version 0.95 beta) works only for xenon and only when it is liquid, but future upgrades will include other elements, including argon, and other phases. NEST is packaged as a new physics process (currently just G4S1Light--S2 will be part of a very near-future upgrade) which you can compile and link against with your own Geant4 simulation by simply editing your physics list appropriately. (Details are in the readme included with your download.) NEST is designed to be easily used with any Geant4 simulation application with a couple of easy changes to your code. If there is interest, NEST may also be programmed for FLUKA, PENELOPE, MCNP, and other programs some day.

NEST is essentially an add-on module for the existing Geant4 simulation package that incorporates more detailed physics than is currently available into the simulation of scintillation. In standard Geant4, one can manually set the scintillation yield for different particle types with G4Scintillation, but there is no fundamental underlying model for recombination physics, nor any distinction between light from direct excitation or recombination of ionization electrons, or any treatment of the dependence of scintillation light yield upon electric field magnitude. However, NEST changes all that. In addition, the Birks' Law for scintillation which Geant currently implements breaks down at low energy (high-dE/dx), necessitating the use of another approach, the Thomas-Imel box model, which we implement in NEST as taking over from Birks' Law in the appropriate energy regime. We also make the application of Birks' Law more transparent to the end user.

NEST is of particular use for low-energy nuclear recoils like you'd see from dark matter. Currently, Geant4 makes no effort to implement the proper scintillation reduction for nuclear recoils vis-a-vis electron recoils in a liquid noble like xenon, and NEST fixes that. If there sufficient excitement and enthusiasm for NEST, it may be included with future release of Geant. But first and foremost, everyone please download it and test it out! See if it can predict/postdict your very own experimental data.