Search for Exclusive Gamma Gamma Production in Hadron-Hadron Collisions

Abstract

We have searched for exclusive 2-photon production in proton-antiproton collisions at sqrt{s} = 1.96 TeV, using 532/pb of integrated luminosity taken by the Run II Collider Detector at Fermilab. The event signature requires two electromagnetic showers, each with transverse energy E_T > 5 GeV and pseudorapidity |eta|<1.0, with no other particles detected in the event. Three candidate events are observed. We discuss the consistency of the three events with gamma-gamma, pi0-pi0, or eta-eta production. The probability that other processes fluctuate to 3 events or more is 1.7x10^-4. An upper limit on the cross section of p+pbar --> p+gamma-gamma+pbar is set at 410 fb with 95% confidence level.

Figures (2)

• Figure 1: The dominant diagram for central exclusive $\gamma\gamma$ production in $p\bar{p}$ collisions. The primary process is $gg\rightarrow\gamma\gamma$ through quark loops, with a screening gluon to cancel the exchanged color.
• Figure 2: The simulated distribution for $\chi^2_{\rm CES}$ for prompt photons (solid histogram), and $\pi^\circ \to\gamma\gamma$ decays (dashed histogram). In all cases $E_T$ is required to be between $5$ and $7$ GeV.