Observation of Single-Top-Quark Production in Association with a Photon Using the ATLAS Detector

Area of Science:

• High Energy Physics
• Particle Physics
• Quantum Chromodynamics

Background:

• The Standard Model of particle physics describes fundamental particles and forces.
• Top quarks are the heaviest known elementary particles.
• Electroweak interactions are fundamental forces described by the Standard Model.

Purpose of the Study:

• To report the observation of single top quarks produced concurrently with a photon.
• To directly probe the electroweak coupling of the top quark.
• To measure the fiducial cross section of this process.

Main Methods:

• Utilized 139 fb⁻¹ of 13 TeV proton-proton collision data.
• Data collected using the ATLAS detector at the Large Hadron Collider.
• Analysis required a photon with transverse momentum > 20 GeV within detector acceptance.

Main Results:

• Measured a fiducial cross section of 688 ± 23 (stat) -71+75 (syst) fb.
• This measurement probes the electroweak coupling of the top quark.
• The measured cross section is compared to the Standard Model prediction.

Conclusions:

• The observation provides direct insight into the top quark's electroweak interactions.
• The measured cross section deviates from the Standard Model prediction.
• This finding contributes to precision measurements in high-energy physics.