Selected Topics in the searches for the SM Higgs boson in ATLAS

One of the main goals of the Large Hadron Collider at CERN is to try understand the dynamics responsible for the EW symmetry breaking which, in the standard model (SM) is achieved by the Higgs mechanism. Although this model has in part been corroborated by indirect measurements, one of its most striking prediction, the existence of a scalar particle has eluded experiments. Its direct search is an outstanding part of the LHC research program. At tree level, the Higgs boson mass is essentially a free parameter of the theory. However, the direct search for the SM Higgs boson at the CERN LEP e+e-collider has constrained its mass to be greater than 114.4 GeV/c2 (95% CL) and the electroweak fit suggests that the Higgs boson mass be smaller than 154 GeV/c2 (95% CL). The ATLAS experiment at LHC will be able to discover the SM Higgs boson if it exists, its discovery potential has been recently reappraised and will be presented. The channels such as the diphoton and VBF tautau at relatively low masses (m<130-140 GeV) will be emphasized.