Measurement of the differential cross section for the production of an isolated photon with associated jet in ppbar collisions at sqrt(s)=1.96 TeV

Abstract

The process ppbar -> photon + jet + X is studied using 1.0 fb^-1 of data collected by the D0 detector at the Fermilab Tevatron ppbar collider at a center-of-mass energy sqrt(s)=1.96 TeV. Photons are reconstructed in the central rapidity region |y_gamma|<1.0 with transverse momenta in the range 30<Pt_gamma<400 GeV while jets are reconstructed in either the central |y_jet|<0.8 or forward 1.5<|y_jet|<2.5 rapidity intervals with Pt_jet>15 GeV. The differential cross section d^3sigma/dPt_gamma dy_gamma dy_jet is measured as a function of Pt_gamma in four regions, differing by the relative orientations of the photon and the jet in rapidity. Ratios between the differential cross sections in each region are also presented. Next-to-leading order QCD predictions using different parameterizations of parton distribution functions and theoretical scale choices are compared to the data. The predictions do not simultaneously describe the measured normalization and Pt_gamma dependence of the cross section in any of the four measured regions.

Figures (10)

• Figure 1: The fraction of events, estimated using the pythia event generator, produced via the $qg \to q\gamma$ subprocess relative to the total associated production of a direct photon and a jet for each of the four measured configurations of the leading jet and leading photon rapidities.
• Figure 2: Normalized distribution of the ANN output $O_{\rm NN}$ for data, $\gamma + \mathrm{jet}$ signal MC, and dijet background MC events for $44<p_{T}^{\gamma}<50$ GeV after application of the main selection criteria.
• Figure 3: Normalized distribution of the ANN output $O_{\rm NN}$ for electrons from $Z^0$ boson decays in data and MC events.
• Figure 4: The purity of the selected $p\bar{p} \rightarrow \gamma + \mathrm{jet} + X$ sample as a function of $p_{T}^{\gamma}$ for each measured configuration of photon and jet rapidities. The results of the $1 - \exp(a + bp_T^\gamma)$ functional fits are shown by the solid lines, together with the systematic uncertainties (dotted lines), and the total uncertainties (dashed lines).
• Figure 5: The total and main sources of systematic uncertainty for the cross section measured in the $|y^{\mathrm{jet}}|\!<\!0.8$, $y^{\mathrm{\gamma}}\!\cdot\! y^{\mathrm{jet}}>0$ rapidity region.