Spectral caustics in laser assisted Breit-Wheeler process

Understand

Electron-positron pair production by the Breit-Wheeler process embedded in a strong laser pulse is analyzed.

• The transverse momentum spectrum displays prominent peaks which are interpreted as caustics, the positions of which are accessible by the stationary phases.
• Examples are given for the superposition of an XFEL beam with an optical high-intensity laser beam.
• Such a configuration is available, e.g., at LCLS at present and at European XFEL in near future.