Search for Standard Model Higgs Boson in $H\rightarrow WW^{*}\rightarrow l\nu l\nu$ Decay Mode with ATLAS Detector at $\sqrt{s}=7$ TeV

Standard Model is already very successful to explain many experimental results in High Energy Physics (HEP). One of the missing parts of Standard Model is the origin of particle mass. Higgs mechanism was proposed to explain the particle mass and predicts another boson called Higgs boson. So finding Higgs boson is a way to prove the Higgs mechanism. If Higgs boson exists, the origin of mass in Standard Model can be understood. That is one of the main motivations to build Large Hadron Collider at CERN. A search for the Standard Model Higgs boson decaying into two W bosons with di-lepton final states is performed using proton-proton collision data at center-of-mass energy of 7 TeV at the Large Hadron Collider. The data is collected by ATLAS detector during 2011 and corresponding to an integrated luminosity 4.7 $\text{fb}^{-1}$. The transverse mass of WW system is used to discriminate signal and background. No significant excess is observed with current data. A Standard Model Higgs boson with a mass in the range between 133 GeV and 258 GeV is excluded at 95% confidence level. The expected exclusion range is from 127 GeV to 233 GeV.