Reconstructing the Higgs signal from ATLAS data

Abstract

After being hunted for about half a century since its prediction by Peter Higgs, the Higgs boson was nally discovered by CERN at the Large Hadron Collider (LHC) in July 2012. The experimental con rmation of its existence marked the last step of completing the Standard Model of electroweak and strong interactions, and started the era of Higgs precision tests to look for new physics. This discovery is particularly important, since it con rms the consistency of the Higgs mechanism in generating particle masses through the rst ever discovered scalar eld. In this master degree thesis, we take a deeper look at the way the Higgs has been discovered at LHC. Firstly, we aim attention at the whole process taking place at LHC, by focusing particularly on the pp ! H ! ZZ

! 4 leptons golden channel. Starting from the proton-proton collision, all the way to the detection of the nal state four leptons in the ATLAS detector. Secondly, taking MadGraph5 aMC@NLO as our event generator, we focus on the simulation of the parton collision events leading us to the four leptons nal state. Here, we lay stress upon the way our knowledge about Standard Model interactions, parton showering, hadronization and detector processes is involved in simulating events. Lastly, we make use of the ATLAS Open Data datasets. We compare the given experimental data with the corresponding simulated ones, then we reconstruct the Higgs signal using some statistical tools. Keywords : Higgs boson, Standard Model, LHC, ATLAS experiment.