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

CDF Collaboration, T. Aaltonen

TL;DR

This study measures the prompt isolated diphoton production cross section in pbarp collisions at sqrt(s)=1.96 TeV with the CDF II detector, using 5.36 fb^-1 of data. A track-ISO based background subtraction and data-driven efficiency corrections enable differential cross sections to be reported across multiple kinematic variables, which are then compared to PYTHIA LO, DIPHOX NLO with fragmentation, and RESBos NNLL calculations. The results show that while the predictions capture the main features in many regions, they fail in low-mass and fragmentation-dominated areas, with RESBos best describing soft-gluon effects at low P_T and PYTHIA requiring photon radiation components to improve agreement. These findings have implications for Higgs to gamma gamma and extra-dimensional searches, highlighting areas where theory models need refinement to accurately describe diphoton production backgrounds.

Abstract

This article reports a measurement of the production cross section of prompt isolated photon pairs in proton-antiproton collisions at \sqrt{s} = 1.96 TeV using the CDF II detector at the Fermilab Tevatron collider. The data correspond to an integrated luminosity of 5.36/fb. The cross section is presented as a function of kinematic variables sensitive to the reaction mechanisms. The results are compared with three perturbative QCD calculations: (1) a leading order parton shower Monte Carlo, (2) a fixed next-to-leading order calculation and (3) a next-to-leading order/next-to-next-to-leading-log resummed calculation. The comparisons show that, within their known limitations, all calculations predict the main features of the data, but no calculation adequately describes all aspects of the data.

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

TL;DR

This study measures the prompt isolated diphoton production cross section in pbarp collisions at sqrt(s)=1.96 TeV with the CDF II detector, using 5.36 fb^-1 of data. A track-ISO based background subtraction and data-driven efficiency corrections enable differential cross sections to be reported across multiple kinematic variables, which are then compared to PYTHIA LO, DIPHOX NLO with fragmentation, and RESBos NNLL calculations. The results show that while the predictions capture the main features in many regions, they fail in low-mass and fragmentation-dominated areas, with RESBos best describing soft-gluon effects at low P_T and PYTHIA requiring photon radiation components to improve agreement. These findings have implications for Higgs to gamma gamma and extra-dimensional searches, highlighting areas where theory models need refinement to accurately describe diphoton production backgrounds.

Abstract

This article reports a measurement of the production cross section of prompt isolated photon pairs in proton-antiproton collisions at \sqrt{s} = 1.96 TeV using the CDF II detector at the Fermilab Tevatron collider. The data correspond to an integrated luminosity of 5.36/fb. The cross section is presented as a function of kinematic variables sensitive to the reaction mechanisms. The results are compared with three perturbative QCD calculations: (1) a leading order parton shower Monte Carlo, (2) a fixed next-to-leading order calculation and (3) a next-to-leading order/next-to-next-to-leading-log resummed calculation. The comparisons show that, within their known limitations, all calculations predict the main features of the data, but no calculation adequately describes all aspects of the data.

Paper Structure

This paper contains 17 sections, 17 equations, 21 figures, 10 tables.

Table of Contents

  1. Introduction
  2. Detector Overview
  3. Data Selection and Event Reconstruction
  4. Cross Section Measurement
  5. Background Subtraction
  6. Event Reconstruction and Selection Efficiency
  7. Corrections and Tests with the $Z^0\rightarrow e^+e^-$ Sample
  8. Results
  9. Theoretical Calculations
  10. Kinematic Variables
  11. Differential Cross Sections Without Additional Kinematic Cut
  12. Differential Cross Sections for $P_{\rm T}$$<$$M$ Kinematics
  13. Differential Cross Sections for $P_{\rm T}$$>$$M$ Kinematics
  14. Conclusions
  15. Acknowledgements
  16. ...and 2 more sections

Figures (21)

  • Figure 1: Basic diagrams for prompt diphoton production: (a-b) direct, (c-d) one-photon radiation from an initial- (ISR) or final-state quark (FSR), (e) fragmentation where one photon is emitted along the direction of a final-state quark taking almost all of its energy. The symbol $\otimes$ denotes the non-perturbative mechanism of the fragmentation process (FRAG).
  • Figure 2: The track-ISO distribution in signal (black--solid) and background (red--dashed) events.
  • Figure 3: Signal (left) and background (right) efficiencies for track-ISO$<$1 GeV. The shaded area is the total systematic uncertainty.
  • Figure 4: Relative systematic uncertainties on the signal (left) and background (right) efficiencies for track-ISO$<$1 GeV.
  • Figure 5: Comparison of track-ISO$<$1 GeV efficiencies in complementary cones from data (squares), signal MC (triangles) and background MC (circles).
  • ...and 16 more figures