Precision Measurement of Trident Production in Strong Electromagnetic Fields

We demonstrate experimentally that the trident process <math display="inline"><msup><mi>e</mi><mo>-</mo></msup><mo stretchy="false">→</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 display="inline"><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.