Direct top-quark decay width measurement in the lepton+jets channel at with the ATLAS experiment

Area of Science:

• Particle Physics
• High-Energy Physics
• Quantum Chromodynamics

Background:

• The top quark is the heaviest known elementary particle.
• Understanding its properties, like decay width, is crucial for testing the Standard Model.
• Direct measurements provide stringent tests of theoretical predictions.

Purpose of the Study:

• To directly measure the decay width of the top quark.
• To compare the measured value with the Standard Model prediction.
• To contribute to precision measurements in high-energy physics.

Main Methods:

• Utilized a large dataset of proton-proton collisions at 8 TeV from the ATLAS detector.
• Analyzed events in the lepton+jets final state.
• Employed a template fit to kinematic distributions of decaying top quarks.

Main Results:

• The top quark decay width was measured directly.
• The result is consistent with the Standard Model prediction.
• A specific value for the decay width was obtained at a top-quark mass of 172.5 GeV.

Conclusions:

• The direct measurement confirms the Standard Model's accuracy regarding top quark properties.
• This study enhances the precision of top quark parameter measurements.
• Further precision measurements will continue to probe the limits of the Standard Model.