Measurement of the photon identification efficiencies with the ATLAS detector using LHC Run-1 data

Area of Science:

• High Energy Physics
• Particle Physics
• Experimental Physics

Background:

• Accurate reconstruction and identification of prompt photons are essential for various physics analyses at the Large Hadron Collider (LHC).
• The ATLAS detector's capabilities for detecting photons are continuously refined through algorithm development and efficiency measurements.

Purpose of the Study:

• To describe the algorithms used by the ATLAS Collaboration for prompt photon reconstruction and identification.
• To report measurements of photon identification efficiencies using proton-proton collision data.
• To provide data-driven correction factors for improving the accuracy of physics measurements involving photons.

Main Methods:

• Utilized proton-proton collision data collected by the ATLAS experiment at the LHC at center-of-mass energies of 7 TeV and 8 TeV.
• Measured photon identification efficiencies separately for converted and unconverted photons across different pseudorapidity regions and transverse momenta.
• Combined three data-driven techniques to determine efficiency ratios, comparing them with detector simulation predictions.

Main Results:

• Photon identification efficiencies were measured for transverse momenta ranging from 10 GeV to 1.5 TeV.
• Data-to-simulation efficiency ratios were determined, serving as correction factors for physics measurements.
• Uncertainties in these correction factors ranged from 0.5% to 10% for 7 TeV data and 0.5% to 5.6% for 8 TeV data.

Conclusions:

• The study provides precise measurements of prompt photon identification efficiencies at the LHC.
• The derived data-to-simulation correction factors are vital for enhancing the precision of future physics analyses utilizing prompt photons.
• The developed algorithms and measured efficiencies contribute to the ATLAS experiment's comprehensive physics program.