Direct measurement of the Chudakov effect

Area of Science:

• Particle Physics
• High-Energy Physics
• Electromagnetic Interactions

Background:

• Pair production is a fundamental process in high-energy physics.
• Understanding energy loss mechanisms is crucial for particle detection and analysis.
• The Chudakov effect describes screening phenomena in charged particle interactions.

Purpose of the Study:

• To experimentally investigate the energy loss of electron-positron pairs created by photons.
• To examine the influence of internal screening on pair energy loss.
• To compare experimental results with theoretical predictions, including the Chudakov effect.

Main Methods:

• Generating electron-positron pairs from 1-178 GeV photons interacting with a thin gold (Au) target.
• Detecting the pairs using a Charge-Coupled Device (CCD) detector positioned near the creation vertex.
• Utilizing calorimetry to directly measure the energy of the detected pairs.

Main Results:

• Observed a restricted energy loss for pairs detected close to the creation vertex.
• Attributed the reduced energy loss to the internal screening effect of the pair's constituent charges.
• Found good qualitative agreement with the Chudakov effect.
• Identified a quantitative disagreement with existing theoretical models.

Conclusions:

• The study confirms the phenomenon of reduced energy loss in pairs due to internal screening.
• Experimental data provides valuable insights into electromagnetic interactions at high energies.
• Discrepancies highlight the need for refined theoretical models for pair energy loss and screening effects.