Search for dark photons decaying to muons or electrons in Higgs decays at ATLAS

Student: Alessandro Biondini
Supervisor: Monica D'Onofrio

Dark photons (Z_D) are an excellent candidate for dark matter. They can additionally explain the cosmic electron/positron excesses observed in a number of experiments. The photons can be produced in Higgs decays via H->Z Z_D and, if the dark U(1) is broken by a hidden-sector Higgs mechanism by H->Z_DZ_D decays. This study would search for dark photons that decay to electrons or muons, such that the events would have four leptons in the final state. The student would perform a complete analysis of the 2015-2018 data from the ATLAS experiment, using advanced techniques in terms of machine learning to develop algorithms for identification of leptons. The LHC would provide the world’s best sensitivity at masses above 10 GeV.