Search For Higgs Boson Pair Production in the $γγb\bar{b}$ Final State using $pp$ Collision Data at $\sqrt{s}=8$ TeV from the ATLAS Detector

Abstract

Searches are performed for resonant and non-resonant Higgs boson pair production in the $γγb\bar{b}$ final state using 20 fb$^{-1}$ of proton-proton collisions at a center-of-mass energy of 8 TeV recorded with the ATLAS detector at the CERN Large Hadron Collider. A 95% confidence level upper limit on the cross section times branching ratio of non-resonant production is set at 2.2 pb, while the expected limit is 1.0 pb. The difference derives from a modest excess of events, corresponding to 2.4 standard deviations from the background-only hypothesis. The limit observed in the search for a narrow $X \to hh$ resonance ranges between 0.7 and 3.5 pb as a function of the resonance mass.

Figures (3)

• Figure 1: (Upper plot) Diphoton invariant mass spectrum for data and the corresponding fitted signal and background in the signal region for the non-resonance search. (Lower plot) The diphoton invariant mass spectrum in the continuum background from events with fewer than two $b$-tags and the corresponding fitted curve, the shape of which is also used in the upper plot.
• Figure 2: (Upper plot) The constrained four-object invariant mass, $m_{\gamma\gamma jj}$, for data events in the resonance signal region. The expected backgrounds are also shown. A narrow width resonance at 300 GeV is displayed for comparison only. (Lower plot) The diphoton invariant mass spectrum in the continuum background from events with fewer than two $b$-tags and the corresponding fitted curve, the shape of which is also used in the upper plot.
• Figure 3: A 95% $CL$ upper limit on the cross section times branching ratio of a narrow resonance decaying to pairs of Higgs bosons as a function of $m_X$ (see text for more details).