Overview
- Using CERN’s Super Proton Synchrotron and HiRadMat, researchers generated electron–positron pairs and sent them through a meter-long ambient plasma to create a scaled analogue of blazar-driven cascades.
- Measurements show the pair beam stayed narrow with minimal self-generated magnetic fields, indicating beam–plasma instabilities are too weak to dissipate the cascade energy.
- Extrapolated to cosmic scales, the results support the view that weak intergalactic magnetic fields deflect secondary GeV gamma rays out of our line of sight.
- The study appears in PNAS and is supported by some of the largest OSIRIS particle-in-cell simulations performed for beam–plasma interactions.
- Researchers say the findings sharpen questions about how such intergalactic fields were seeded in the early universe, with upcoming CTAO observations expected to probe the interpretation.