Bounding elastic photon-photon scattering at √s ≈ 1 MeV using a laser-plasma platform

Journal article

We report on a direct search for elastic photon-photon scattering using x-ray and 𝛾 photons from a laser-plasma based experiment. A 𝛾 photon beam produced by a laser wak­field accelerator provided a broadband 𝛾 spectrum extending to above 𝐸𝛾 = 200 MeV. These were collided with a dense x-ray field produced by the emission from a laser heated germanium foil at 𝐸𝑥 ≈ 1.4 keV, corresponding to an invariant mass of √𝑠 = 1.22 ± 0.22 MeV. In these asymmetric collisions elastic scattering removes one x-ray and one high-energy 𝛾 photon and outputs two lower energy 𝛾 photons. No changes in the 𝛾 photon spectrum were observed as a result of the collisions allowing us to place a 95% upper bound on the cross section of 1.5 × 1015 μb. Although far from the QED prediction, this represents the lowest upper limit obtained so far for √𝑠 ≲ 1 MeV.

Authors: Watt, R; Kettle, B; Gerstmayr, E; King, B; Alejo, A

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Elsevier
• Journal: Physics Letters B
• Volume: 861
• Article number: 139247
• Publication date: 2025-01-10
• Acceptance date: 2025-01-07
• DOI: 10.1016/j.physletb.2025.139247
• EISSN: 1873-2445
• ISSN: 0370-2693
• Language: English