Search for signatures of extra dimensions in the diphoton mass spectrum at the Large Hadron Collider

Abstract

A search for signatures of extra dimensions in the diphoton invariant-mass spectrum has been performed with the CMS detector at the LHC. No excess of events above the standard model expectation is observed using a data sample collected in proton-proton collisions at sqrt(s) = 7 TeV corresponding to an integrated luminosity of 2.2 inverse femtobarns. In the context of the large-extra-dimensions model, lower limits are set on the effective Planck scale in the range of 2.3-3.8 TeV at the 95% confidence level. These limits are the most restrictive bounds on virtual-graviton exchange to date. The most restrictive lower limits to date are also set on the mass of the first graviton excitation in the Randall-Sundrum model in the range of 0.86-1.84 TeV, for values of the associated coupling parameter between 0.01 and 0.10.

Figures (3)

• Figure 1: Observed event yields (points with error bars) and background expectations (filled solid histograms) as a function of the diphoton invariant mass. Photons are required to be isolated, with $E_{\mathrm{T}}\xspace>70$$\,\text{Ge\spaceV}$ and $|\eta|<1.44$. The shaded band around the background estimation corresponds to the average systematic uncertainty over the spectrum. The precise per-bin uncertainty is not provided for the sake of clarity. The last bin includes the sum of all contributions for $M_{\gamma\gamma}>2.0\,\text{Te\spaceV}\xspace$. The simulated distributions for two, non-excluded signal hypotheses are shown for comparison as dotted (ADD) and dashed (RS) lines.
• Figure 2: Signal cross section $S$ parameterization as a function of the strength of the ED effects, $\eta_G$ (top) and as a function of $1/M_\text{S}\xspace^4$ for the HLZ $n_\textsc{ed}\xspace=2$ case (bottom).
• Figure 3: The 95% CL exclusion region for the RS1 graviton model in the $M_1$--$\tilde{k}$ plane. The expected limits coincide very closely with the measured limits and so are not shown in the figure. Also shown are bounds due to electroweak constraints and naturalness ($\Lambda_{\pi}>10\,\text{Te\spaceV}\xspace$). Perturbativity requirements bound $\tilde{k}\lesssim0.10$.