This presentation will focus on my thesis work on the 2 Higgs Doublet Model (2HDM) in the D0 experiment. I shall briefly present the D0 detector and discuss its performance, with particular attention on the liquid Argon calorimeter and its calibration. I shall then describe the 2HDM, for which lepton number violation is possible. We have constrained the coupling responsible for this violation with recent data on the muon anomalous magnetic moment. Then we have used these constraints to determine the discovery potential of the process H0/A0 -> tau muon with a full simulation of the D0 detector.