Alexander J. Macleod (for the LUXE collaboration)
The combination of energetic electron beams, delivered from conventional accelerators at a high repetition rate, and ultraintense lasers, makes it possible to perform precision measurements of strong-field QED. The LUXE collaboration aims to perform precision measurements of nonlinear Compton scattering and Breit-Wheeler pair creation in the transition from the perturbative to nonperturbative regimes. Here we present an overview of recent developments in the modelling of strong-field QED processes, which are needed to reach the required precision of a few percent for intensity parameters 0.1<ξ<10. We discuss how to go from plane wave QED results to numerical simulations and present predicted signals and error estimates.
Comments: Contribution to LPHYS'21 workshop. 10 pages, 8 figures
Universal structure of radiative QED amplitudes at one loop: https://arxiv.org/abs/2112.07570
Tim Engel, Adrian Signer, Yannick Ulrich
We present two novel results about the universal structure of radiative QED amplitudes in the soft and in the collinear limit. On the one hand, we extend the well-known Low-Burnett-Kroll theorem to the one-loop level and give the explicit relation between the radiative and non-radiative amplitude at subleading power in the soft limit. On the other hand, we consider a factorisation formula at leading power in the limit where the emitted photon becomes collinear to a light fermion and provide the corresponding one-loop splitting function. In addition to being interesting in their own right these findings are particularly relevant in the context of fully-differential higher-order QED calculations. One of the main challenges in this regard is the numerical stability of radiative contributions in the soft and collinear regions. The results presented here allow for a stabilisation of real-virtual amplitudes in these delicate phase-space regions by switching to the corresponding approximation without the need of explicit computations.
Comments: 25 pages, 7 figures
Soft photon bremsstrahlung at next-to-leading power: https://arxiv.org/abs/2112.08329
Domenico Bonocore, Anna Kulesza
The emission of soft radiation provides a fundamental probe of the consistency of the underlying Quantum Field Theory. Correspondingly, the measurement of the soft photon bremsstrahlung, such as the one proposed with the planned future upgrade of the ALICE experiment at the LHC, is of great interest. In this letter we explore the possibility to implement analytic techniques that have been recently developed for soft gluon resummation at Next-to-Leading-Power (NLP) in the context of the soft photon spectrum. We provide a formula for the differential cross-section with shifted kinematics that is particularly suitable for numerical implementations. We also discuss the impact of loop corrections to Low's theorem due to radiative jet functions.
Comments: 15 pages, 2 figures