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arXiv · 2407.12915

Bounding elastic photon-photon scattering at $\sqrt s \approx 1\,$MeV using a laser-plasma platform

R. Watt·B. Kettle·E. Gerstmayr·B. King·A. Alejo·S. Astbury·C. Baird·S. Bohlen·M. Campbell·C. Colgan·D. Dannheim·C. Gregory·H. Harsh·P. Hatfield·J. Hinojosa·D. Hollatz·Y. Katzir·J. Morton·C. D. Murphy·A. Nurnberg·J. Osterhoff·G. Pérez-Callejo·K. Põder·P. P. Rajeev·C. Roedel·F. Roeder·F. C. Salgado·G. M. Samarin·G. Sarri·A. Seidel·C. Spindloe·S. Steinke·M. J. V. Streeter·A. G. R. Thomas·C. Underwood·W. Wu·M. Zepf·S. J. Rose·S. P. D. Mangles
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Abstract

We report on a direct search for elastic photon-photon scattering using x-ray and $\gamma$ photons from a laser-plasma based experiment. A gamma photon beam produced by a laser wakefield accelerator provided a broadband gamma spectrum extending to above $E_\gamma = 200$ MeV. These were collided with a dense x-ray field produced by the emission from a laser heated germanium foil at $E_x \approx 1.4$ keV, corresponding to an invariant mass of $\sqrt{s} = 1.22 \pm 0.22$ MeV. In these asymmetric collisions elastic scattering removes one x-ray and one high-energy $\gamma$ photon and outputs two lower energy $\gamma$ photons. No changes in the $\gamma$ photon spectrum were observed as a result of the collisions allowing us to place a 95% upper bound on the cross section of $1.5 \times 10^{15}\,\mu$b. Although far from the QED prediction, this represents the lowest upper limit obtained so far for $\sqrt{s} \lesssim 1$ MeV.

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R. Watt, B. Kettle, E. Gerstmayr, B. King, A. Alejo, S. Astbury, C. Baird, S. Bohlen, M. Campbell, C. Colgan, D. Dannheim, C. Gregory, H. Harsh, P. Hatfield, J. Hinojosa, D. Hollatz, Y. Katzir, J. Morton, C. D. Murphy, A. Nurnberg, J. Osterhoff, G. Pérez-Callejo, K. Põder, P. P. Rajeev, C. Roedel, F. Roeder, F. C. Salgado, G. M. Samarin, G. Sarri, A. Seidel, C. Spindloe, S. Steinke, M. J. V. Streeter, A. G. R. Thomas, C. Underwood, W. Wu, M. Zepf, S. J. Rose, S. P. D. Mangles. 2024-07-17. Bounding elastic photon-photon scattering at $\sqrt s \approx 1\,$MeV using a laser-plasma platform. https://doi.org/10.1016/j.physletb.2025.139247

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