Search for extra dimensions in diphoton events from proton–proton collisions at $\sqrt {s} = 7\,$ TeV in the ATLAS detector at the LHC

Abstract

The large difference between the Planck scale and the electroweak
\nscale, known as the hierarchy problem, is addressed in certain models through
\nthe postulate of extra spatial dimensions. A search for evidence of extra spatial
\ndimensions in the diphoton channel has been performed using the full set of
\nproton–proton collisions at √s = 7 TeV recorded in 2011 with the ATLAS
\ndetector at the CERN Large Hadron Collider. This dataset corresponds to an
\nintegrated luminosity of 4.9 fb−1. The diphoton invariant mass spectrum is
\nobserved to be in good agreement with the Standard Model expectation. In
\nthe context of the model proposed by Arkani–Hamed, Dimopoulos and Dvali,
\n95% confidence level lower limits of between 2.52 and 3.92 TeV are set on the
\nultraviolet cutoff scale MS depending on the number of extra dimensions and
\nthe theoretical formalism used. In the context of the Randall–Sundrum model,
\na lower limit of 2.06 (1.00) TeV at 95% confidence level is set on the mass of
\nthe lightest graviton for couplings of k/MPl = 0.1(0.01). Combining with the
\nATLAS dilepton searches based on the 2011 data, the 95% confidence level
\nlower limit on the Randall–Sundrum graviton mass is further tightened to 2.23
\n(1.03) TeV for k/MPl = 0.1(0.01).