Search for Diphoton Events with Large Missing Transverse Energy in 7 TeV Proton-Proton Collisions with the ATLAS Detector

A search for diphoton events with large missing transverse energy is presented. The data were collected with the ATLAS detector in proton-proton collisions at $\sqrt{s}=7\mathrm{TeV}$ at the CERN Large Hadron Collider and correspond to an integrated luminosity of $3.1{\mathrm{pb}}^{-1}$. No excess of such events is observed above the standard model background prediction. In the context of a specific model with one universal extra dimension with compactification radius $R$ and gravity-induced decays, values of $1/R<729\mathrm{GeV}$ are excluded at 95% C. L., providing the most sensitive limit on this model to date.

Figure 1

$E_T$ spectrum of the leading photon for the $\gamma \gamma$ candidate sample and for UED $1/R=700\mathrm{GeV}$ MC events (normalized to 100 times the leading order (LO) cross section).

Figure 2

$E_T^{\mathrm{miss}}$ spectra for the $\gamma \gamma$ candidates, for the $Z\to ee$ and misidentified jet samples used to model the QCD background (each normalized to the number of $\gamma \gamma$ candidates with $E_T^{\mathrm{miss}}<20\mathrm{GeV}$), and for the $W(\to e\nu )+\mathrm{\text{jets}}/\gamma$ background (normalized to its expected total of $\approx 0.4$ events). Variable sized bins are used, and the vertical error bars and shaded bands show the statistical errors.

Figure 3

$E_T^{\mathrm{miss}}$ spectrum for the $\gamma \gamma$ candidates, compared to the total SM background as estimated from data. Also shown are the expected UED signals for $1/R=500\mathrm{GeV}$ and 700 GeV. Variable sized bins are used, and the vertical error bars and shaded bands show the statistical errors.

Figure 4

$95\%\mathrm{C}.\mathrm{L}.$ upper limits on the UED production cross section, and the LO theory cross section prediction, as a function of $1/R$. The shaded band shows the PDF uncertainty.