Search for Randall-Sundrum Gravitons in Dilepton and Diphoton Final States

We report the first direct search for the Kaluza-Klein (KK) modes of Randall-Sundrum gravitons using dielectron, dimuon, and diphoton events observed with the D0 detector operating at the Fermilab Tevatron $p\overline{p}$ Collider at $\sqrt{s}=1.96\mathrm{TeV}$. No evidence for resonant production of gravitons has been found in the data corresponding to an integrated luminosity of $\approx 260{\mathrm{pb}}^{-1}$. Lower limits on the mass of the first KK mode at the 95% C.L. have been set between 250 and 785 GeV, depending on its coupling to standard model particles.

Figure 1

Invariant mass spectrum in the (a) diEM and (b) dimuon channels. The points with error bars are data and the solid line is the overall background [dark shading in (a) represents instrumental background]. Also shown with an open histogram is the signal from an RS graviton with mass $M_1=300\mathrm{GeV}$ and coupling $k/{\overline{M}}_{\mathrm{Pl}}=0.05$.

Figure 2

The 95% C.L. upper limits on $\sigma (p\overline{p}\to G^{(1)}\to \ell \ell )$, as a function of the graviton mass. The upper (lower) solid line with points corresponds to the dimuon (diEM) channel. The dashed lines with points represent the expected limits. Also shown with a series of smooth lines the production cross sections for various values of $k/{\overline{M}}_{\mathrm{Pl}}$ between 0.01 and 0.1.

Figure 3

95% C.L. exclusion limits on the RS model parameters $M_1$ and $k/{\overline{M}}_{\mathrm{Pl}}$. The light-shaded area has been excluded in the dimuon channel; the medium-shaded area shows the extension of the limits obtained in the diEM channel; the dotted line corresponds to the combination of the two channels. The area below the dashed-dotted line is excluded from the precision electroweak data (see Ref. [2]). The dark shaded area in the lower right-hand corner corresponds to ${\Lambda }_{\pi }>10\mathrm{TeV}$, which requires a significant amount of fine-tuning.