Physical Review Letters 99,24 (2007) 20021-7;
We have searched for exclusive gamma gamma production in proton-antiproton collisions at root s = 1.96 TeV, using 532 pb(-1) 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, pi(0)pi(0), or eta eta production. The probability that other processes fluctuate to >= 3 events is 1.7x10(-4). An upper limit on the cross section of p (p) over bar -> p + gamma gamma + (p) over bar production is set at 410 fb with 95% confidence level.
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