Search for High-Mass $e^{+}{e}^{-}$ Resonances in $p\overline{p}$ Collisions at $\sqrt{s}=1.96\mathrm{TeV}$

A search for high-mass resonances in the $e^{+}{e}^{-}$ final state is presented based on $2.5{\mathrm{fb}}^{-1}$ of $\sqrt{s}=1.96\mathrm{TeV}$ $p\overline{p}$ collision data from the CDF II detector at the Fermilab Tevatron. The largest excess over the standard model prediction is at an $e^{+}{e}^{-}$ invariant mass of $240\mathrm{GeV}/c^2$. The probability of observing such an excess arising from fluctuations in the standard model anywhere in the mass range of $150–1000\mathrm{GeV}/c^2$ is 0.6% (equivalent to $2.5\sigma$). We exclude the standard model coupling $Z^{\prime }$ and the Randall-Sundrum graviton for $k/{\overline{M}}_{\mathrm{Pl}}=0.1$ with masses below 963 and $848\mathrm{GeV}/c^2$ at the 95% credibility level, respectively.

Figure 1

Invariant-mass distribution of $e^{+}{e}^{-}$ events compared to the expected backgrounds. Dots with error bars are data. The dark shaded region represents “other SM” background, the light shaded region shows QCD background, and the white region corresponds to $Z/{\gamma }^{*}\to e^{+}{e}^{-}$ background. The inset shows the same for the $240\mathrm{GeV}/c^2$ region. The hatched histogram shows the shape of the expected signal from a $240\mathrm{GeV}/c^2$ spin 1 particle (of negligible intrinsic width) on top of the total background. The hatched region is normalized to the number of excess events seen in the data.

Figure 2

Distribution of maximum $-2\ln \lambda$ in simulated experiments that assume only background. The arrow indicates the value observed in data: $-2\ln \lambda =14.4$.

Figure 3

The upper limits on $\sigma (p\overline{p}\to X)\mathcal{B}(X\to e^{+}{e}^{-})$ as function of the mass of an $X$ particle at the 95% C.L. where $X$ is a spin 1 particle (a) or a spin 2 particle (b) together with model predictions.

Figure 4

$k/{\overline{M}}_{\mathrm{Pl}}$ as a function of RS graviton mass. The shading indicates the region excluded at the 95% credibility level.