In this paper, we present experimental results and numerical simulations of trident production, <math><mrow><msup><mrow><mi>e</mi></mrow><mrow><mo>−</mo></mrow></msup><mo>→</mo><msup><mrow><mi>e</mi></mrow><mrow><mo>−</mo></mrow></msup><msup><mrow><mi>e</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>e</mi></mrow><mrow><mo>−</mo></mrow></msup></mrow></math>, in a strong electromagnetic field. The experiment was conducted at CERN for the purpose of probing the strong-field parameter <math><mi>χ</mi></math> up to 2.4, using a 200 GeV electron beam penetrating a <math><mrow><mn>400</mn><mtext> </mtext><mtext> </mtext><mi>μ</mi><mrow><mi>m</mi></mrow></mrow></math> thick germanium crystal oriented along the <math><mo>⟨</mo><mn>110</mn><mo>⟩</mo></math> axis. For the current experimental parameters we found that the trident process is primarily a two-step process, and show remarkable agreement between theoretical predictions and experimental data. This paper is an extension of the previously published paper [C. F. Nielsen et al., Phys. Rev. Lett. 130, 071601 (2023)] and features new analysis differential in the energy of the produced positron and electron in the trident process. Even for the more demanding differential analysis, we find good agreement between theoretical predictions and experimental data, while a slight discrepancy is found in the high energy tail of the trident spectrum. This discrepancy could be an indication of the direct process, but further investigation is needed due to the large uncertainties in this part of the spectrum. Finally we present a suggestion for a future experiment, aiming to probe the direct process using thin crystals.

Denmark

Christian F. Nielsen

United States

Robert Holtzapple

Mads M. Lund

Jeppe H. Surrow

Allan H. Sørensen

Marc B. Sørensen

Ulrik I. Uggerhøj

Differential measurement of trident production in strong electromagnetic fields

We demonstrate experimentally that the trident process <math><msup><mi>e</mi><mo>−</mo></msup><mo>→</mo><msup><mi>e</mi><mo>−</mo></msup><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup></math> in a strong external field, with a spatial extension comparable to the effective radiation length, is well understood theoretically. The experiment, conducted at CERN, probes values for the strong field parameter <math><mi>χ</mi></math> up to 2.4. Experimental data and theoretical expectations using the local constant field approximation show remarkable agreement over almost 3 orders of magnitude in yield.

Precision Measurement of Trident Production in Strong Electromagnetic Fields