Search for Kaluza-Klein Graviton Emission in $p\overline{p}$ Collisions at $\sqrt{s}=1.8\mathrm{TeV}$ Using the Missing Energy Signature

We report on a search for direct Kaluza-Klein graviton production in a data sample of $84\mathrm{p}{\mathrm{b}}^{\mathrm{-}\mathrm{1}}$ of $p\overline{p}$ collisions at $\sqrt{\mathrm{s}}=1.8\mathrm{TeV}$, recorded by the Collider Detector at Fermilab. We investigate the final state of large missing transverse energy and one or two high energy jets. We compare the data with the predictions from a ($3+1+n$)-dimensional Kaluza-Klein scenario in which gravity becomes strong at the TeV scale. At 95% confidence level (C.L.) for $n=2$, 4, and 6 we exclude an effective Planck scale below 1.0, 0.77, and 0.71 TeV, respectively.

Figure 1

Comparison between data (points) and standard model predictions (boxes) of the ${\mathrm{E̸}}_T$ distribution. There are 284 data events, to be compared with $274\pm 16$ events predicted from standard model sources. The distribution is plotted with a variable bin size; the contents for bin sizes greater than 10 GeV are normalized accordingly. The height of the boxes shows the uncertainty on the standard model prediction.

Figure 2

Comparison between data (points) and standard model predictions (histogram) of the first and second leading jet $E_T$, $\delta {\phi }_{\min }$, and $N_{\mathrm{jet}}$ distributions.

Figure 3

The predicted ${\mathrm{E̸}}_T$ distribution from standard model processes (histogram) and the one from the expected graviton signal (for $n=2$, $M_D=0.6\mathrm{TeV}$, and a $K$ factor of 1.0) added to the standard model (hatched). The signal appears as a smooth excess over the standard model background. The points are the observed data.

Figure 4

The three curves show the number of expected signal events for $n=2$, 4, and 6 extra dimensions as a function of the effective Planck scale $M_D$ for a $K$ factor of 1.0. The straight line shows the 95% C.L. upper limit on the number of signal events.