Search for a Low Mass Standard Model Higgs Boson with the ATLAS Detector at the LHC

In 2011, the ATLAS experiment collected ~4.8 fb-1 of proton-proton collision data at √s = 7 TeV provided by the Large Hadron Collider (LHC). This data set allowed the search for a Standard Model (SM) Higgs Boson in the TeV range. In that paper, the focus is put on the searches of a low mass Higgs in the range [110, 150] GeV. Using the 2011 ATLAS dataset, the combination of all the channels showed that a SM Higgs boson was restricted to live in the region 117.5-118.5 and 122.5-129 GeV. Importantly, an excess of events was observed around 126 GeV but its statistical significance was too small (2.5 standard deviations) to be able to conclude to any discovery yet at the time of the presentation made at the CIPANP2012 conference [1]. These results have been updated in July 4th 2012 using the 2011 dataset and around 5.8 fb-1 of proton-proton collision data at √s = 8 TeV collected in 2012. The present conclusion is that the excess is now significant enough (5.9 standard deviations) to announce the discovery of a new neutral particle with a mass of M=126.0 GeV +/-0.4 GeV (stat.) +/- 0.4 GeV (syst.) whose properties are compatible with those expected from a SM Higgs boson [2]. These proceedings will then describe the published results.