ZH Dark Photon Analysis with the ATLAS Experiment

The standard model (SM) provides a successful description of the fundamental particles which make up the visible matter in our universe and the fundamental forces governing their interactions. However, it is not the final theory as it fails to describe gravitational force and to answer the outstanding questions in particle physics such as the composition of dark matter. The experiments at the large Hadron Collider (LHC) aims to find a way to answer these questions. The discovery of the Higgs boson by the general-purpose experiments, namely, ATLAS and CMS in 2012 revealed the agreement of the data with the predictions of the SM, furthermore, the mechanism by which fundamental particles acquire mass was explained. Multiple searches have studied the final states of the decayed Higgs boson. Dark Photon searches in ATLAS aims to look for 𝛄D which is a massless dark photon coupling to the Higgs through a charged dark sector in ZH production mode, such invisible final states could be a sign of physics beyond the standard model (BSM). Where 𝛄D acts as a mediating particle since particles in the dark sector don’t interact directly with the SM particles. The data used for the ZH dark photon analysis were collected by the ATLAS experiment, where the center of mass energy 𝐞𝐪𝐮𝐚𝐥𝐬 13 TeV. This paper aims to provide an overview of the LHC and ATLAS, followed by a discussion on the computing framework used in the analysis. Finally, the physics signal, background contributions and plotting are described.