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Q: Fachverband Quantenoptik und Photonik
Q 38: Quantum Effects (QED) I
Q 38.8: Vortrag
Mittwoch, 11. März 2020, 15:45–16:00, f442
Quantum radiation reaction in aligned crystals beyond the local constant field approximation. — •Tobias Wistisen and Antonino Di Piazza — Max-Planck-Institut für Kernphysik, Heidelberg, Deutschland
When an electron or a positron hits a crystal target with a small angle of incidence with respect to a crystal symmetry axis or plane, it experiences a strong electromagnetic field. If the particle energy is high enough, one can reach the QED critical (Schwinger) field Ecr = m2c3/(ℏ e) ≈ 1.3 × 1018 V/m in the rest frame of the particle. Quantum radiation reaction corresponds to the emission of multiple photons in this regime. In [1] we investigated this using a positron beam with 180 GeV directed along a crystalline axis in Silicon. The radiation emission process could then be approximated as if taking place in a constant field, in each moment of time, often called the local constant field approximation (LCFA). For lower particle energies this approximation is no longer applicable. With this in mind, a new theoretical model based on a semiclassical approach for calculating radiation emission in the quantum regime beyond the use of the LCFA was devised. In 2017 an experiment, at lower energies, was carried out at the CERN H4 beamline, and we compared the experimentally measured photon emission spectra to the LCFA model, and the new theoretical model. It is seen that the new approach is in convincing agreement with the data, while the LCFA is in disagreement [2].
[1] T.N. Wistisen et. al. Nat. Commun., 9(1):795. Feb. 2018.
[2] T.N. Wistisen et. al. Phys. Rev. Research 1, 033014. Oct. 2019