Observation of Exclusive γγ Production in p(p)over-bar Collisions at √s=1.96 TeV

We have observed exclusive gamma gamma production in proton-antiproton collisions at root s = 1.96 TeV, using data from 1.11 +/- 0.07 fb(-1) integrated luminosity taken by the Run II Collider Detector at Fermilab. We selected events with two electromagnetic showers, each with transverse energy E-T > 2.5 GeV and pseudorapidity |eta| < 1.0, with no other particles detected in -7.4 < eta < +7.4. The two showers have similar ET and azimuthal angle separation Delta phi similar to pi; 34 events have two charged particle tracks, consistent with the QED process p<(p)over bar> --> p + e(+)e(-) + (p) over bar by two-photon exchange, while 43 events have no charged tracks. The number of these events that are exclusive pi(0)pi(0) is consistent with zero and is < 15 at 95% C. L. The cross section for p<(p)over bar> --> p + gamma gamma + (p) over bar with |eta(gamma)| < 1.0 and E-T(gamma) > 2.5 GeV is 2.48(-0.35)(+0.40)(stat)(-0.51)(+0.40)(syst) pb.