Search for the Standard Model Higgs boson in the diphoton decay channel with 4.9 fb-1 of pp collisions at sqrt(s) = 7 TeV with ATLAS

Abstract

A search for the Standard Model Higgs boson is performed in the diphoton decay channel. The data used corresponds to an integrated luminosity of 4.9 fb-1 collected with the ATLAS detector at the Large Hadron Collider in proton-proton collisions at a center-of-mass energy of sqrt(s) = 7 TeV. In the diphoton mass range 110-150 GeV, the largest excess with respect to the background-only hypothesis is observed at 126.5 GeV, with a local significance of 2.8 standard deviations. Taking the look-elsewhere effect into account in the range 110-150 GeV, this significance becomes 1.5 standard deviations. The Standard Model Higgs boson is excluded at 95% confidence level in the mass ranges of 113-115 GeV and 134.5-136 GeV.

Figures (4)

• Figure 1: Invariant mass distribution for the selected data sample, overlaid with the total background (see text). The bottom inset displays the residual of the data with respect to the total background. The Higgs boson expectation for a mass hypothesis of 120 GeV corresponding to the SM cross section is also shown.
• Figure 2: Reconstructed invariant mass distribution for a simulated signal of $m_H=120$ GeV summed over all categories, superimposed with the fit to the signal model.
• Figure 3: The observed local $p_0$, the probability that the background fluctuates to the observed number of events or higher (solid line). The open points indicate the observed local $p_0$ value when energy scale uncertainties are taken into account. The dotted line shows the expected median local $p_0$ for the signal hypothesis when tested at $m_H$.
• Figure 4: Observed and expected 95% CL limits on the SM Higgs boson production normalized to the predicted cross section as a function of $m_H$.