/ Experiment-HEP arXiv:1112.0858

Observation of Exclusive Gamma Gamma Production in $p \bar{p}$ Collisions at $\sqrt{s}=1.96$ TeV

Pages: 7

Abstract: We have observed exclusive $\gamma \gamma$ production in proton-antiproton collisions at $\sqrt{s}$ = 1.96 TeV, using data from 1.11 $\pm$ 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 $E_T$ and azimuthal angle separation $\Delta\phi \sim \pi$; 34 events have two charged particle tracks, consistent with the QED process $p\bar{p} \rightarrow p + e^+e^- + \bar{p}$ 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 $p + \bar{p} \rightarrow p + \gamma \gamma + \bar{p}$ with $|\eta(\gamma)| < 1.0$ and $E_T(\gamma) >$ 2.5 GeV is $2.48^{+0.40}_{-0.35}$(stat)$^{+0.40}{_0.51}$(syst) pb.

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Запись создана 2012-01-24, последняя модификация 2014-01-30

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