Measurement of the Cross Section for Prompt Isolated Diphoton Production in $p\overline{p}$ Collisions at $\sqrt{s}=1.96\mathrm{TeV}$

This Letter reports a measurement of the cross section of prompt isolated photon pair production in $p\overline{p}$ collisions at a total energy $\sqrt{s}=1.96\mathrm{TeV}$ using data of $5.36{\mathrm{fb}}^{-1}$ integrated luminosity collected with the CDF II detector at the Fermilab Tevatron. The measured cross section, differential in basic kinematic variables, is compared with three perturbative QCD predictions, a leading order parton shower calculation and two next-to-leading order calculations. The next-to-leading order calculations reproduce most aspects of the data. By including photon radiation from quarks before and after hard scattering, the parton shower prediction becomes competitive with the next-to-leading order predictions.

Figure 1

The measured differential cross sections compared with three theoretical predictions discussed in the text. The left windows show the absolute comparisons, and the right windows show the fractional deviations of the data from the theoretical predictions. Fractional deviations for pythia refer to the $\gamma \gamma +\gamma j$ calculation. Note that the vertical axis scales differ between fractional deviation plots. The comparisons are made as functions of the diphoton mass (top), transverse momentum (middle), and azimuthal angle difference (bottom). The shaded area around the data points indicates the total systematic uncertainty of the measurement.