Beam-beam limit in e+e- circular colliders

Area of Science:

• Particle physics
• Accelerator physics
• Computational physics

Background:

• Beam-beam effects are a primary limitation for luminosity in circular colliders.
• Exceeding a threshold bunch population results in a reduced luminosity increase rate, known as the beam-beam limit.
• Understanding this limit is crucial for optimizing collider performance.

Purpose of the Study:

• To analyze the onset of the beam-beam limit using simulation methods.
• To identify the underlying phenomena responsible for the beam-beam limit.
• To characterize the beam distributions at the beam-beam limit.

Main Methods:

• Analysis of beam-beam effects using weak-strong and strong-strong simulation models.
• Investigation of incoherent phenomena contributing to the beam-beam limit.
• Examination of equilibrium beam distributions under luminosity limitations.

Main Results:

• The beam-beam limit is primarily driven by incoherent phenomena.
• Simulations show that equilibrium beam distributions deviate from Gaussian profiles when the luminosity is limited.
• The beam-beam limit is estimated to be approximately xi = 0.1 for a B factory with a damping time of several thousand turns.

Conclusions:

• Incoherent effects are the main drivers of the beam-beam limit.
• Non-Gaussian beam distributions are characteristic of the beam-beam limit.
• The findings provide an estimate for the beam-beam limit in specific collider scenarios.