Simulation of dark bremsstrahlung in Geant4

Abstract

A technique for the simulation of dark bremsstrahlung for electrons and muons in Geant4 is presented. The total cross section is calculated using the Weizsäcker-Williams approximation and the outgoing kinematics are produced by scaling events produced in MadGraph/MadEvent to lower incident lepton energies, allowing the simulation to account for thick targets and lepton sources without fixed energies. Compared with dedicated samples produced at an arbitrary particle energy, typical precision of better than 5% is achieved. Program summaryProgram Title: G4DarkBreMCPC Library link to program files:https://doi.org/10.17632/3pxfrz8cmn.1Licensing provisions: Apache-2.0Programming language: C++Nature of problem: To accurately simulate the kinematics of the dark bremsstrahlung process for electrons and muons in thick targets and lepton sources without fixed energies. The process must be included at the level of experimental simulation instead of using initial state event generators to account for the possibility of energy loss through bremsstrahlung or multiple scattering prior to the dark matter interaction. Accurate kinematic simulation of the outgoing lepton are required for optimal experimental sensitivity measurements and appropriate design of search strategies.Solution method: We embed the dark bremsstrahlung process into Geant4. The cross section is calculated using numerical integrals of the Weizsäcker-Williams approximation, and the kinematics are simulated using a scaling technique of MadGraph/MadEvent event libraries. The accuracy of the total cross section and kinematics is validated using MadGraph/MadEvent samples.