Limits on Extra Dimensions and New Particle Production in the Exclusive Photon and Missing Energy Signature in $p\overline{p}$ Collisions at $\sqrt{s}=1.8\mathrm{T}\mathrm{e}\mathrm{V}$

The exclusive $\gamma {\mathrm{E̸}}_T$ signal has a small standard model cross section and is thus a channel sensitive to new physics. This signature is predicted by models with a superlight gravitino or with large extra spatial dimensions. We search for such signals at the Collider Detector at Fermilab, using $87\mathrm{p}{\mathrm{b}}^{\mathrm{-}\mathrm{1}}$ of data at $\sqrt{s}=1.8\mathrm{T}\mathrm{e}\mathrm{V}$, and extract 95% C.L. limits on these processes. A limit of 221 GeV is set on the scale $|F{|}^{1/2}$ in supersymmetric models. For 4, 6, and 8 extra dimensions, model-dependent limits on the fundamental mass scale $M_D$ of 0.55, 0.58, and 0.60 TeV, respectively, are found. We also specify a “pseudo-model-independent” method of comparing the results to theoretical predictions.

Figure 1

Photon $E_T$ spectrum after each stage of cuts.

Figure 2

Plots of (a) acceptance vs ${\eta }^{\gamma }$ and (b) efficiency vs $E_T^{\gamma }$ for the analysis selection. These plots are valid for any exclusive photon and invisible particle process. The error bars are statistical only. The falloff in acceptance at $\left|\eta \right|\simeq 0$ and $\left|\eta \right|\simeq 1$ is due to the folding of the fiducial region of the calorimeter with the longitudinal spread ($\sigma \simeq 30\mathrm{c}\mathrm{m}$) of the $p\overline{p}$ collisions.