## Photons at high energies in intense fields

Wednesday, April 18, 2018 - 3:00pm to 4:00pm

Speaker: Ulrik I. Uggerhøj, Aarhaus

Program Description:

When a high-energy particle, like an electron or a photon, is exposed to a sufficiently intense field, the particle is likely to radiate or convert into an electron-positron pair, respectively. Once the field in the electron rest frame becomes comparable to the QED critical electric field $\mathcal{E}_0=m^2c^3/e\hbar=1.32\cdot10^{16}$ V/cm (corresponding to a magnetic field of $B_0=4.41\cdot10^9$ T), the radiation process changes character and a similar change arises for photons at high energies in an intense field. In the framework of the CERN NA63 we have experimentally investigated these phenomena over the past 20 years, and also addressed questions like “how long time does it take for an electron to produce a photon?"