Radiative reactions in halo effective field theory

In this article we review the recent progress in radiative reaction calculations in halo effective field theory. We look at radiative capture and breakup processes that involve a halo nucleus with a single valence neutron or proton. Looking at [Formula: see text] [Formula: see text],[Formula: see text]n[Formula: see text] and related reactions, the dominant source of theoretical uncertainty in [Formula: see text]- and [Formula: see text]-wave halo nuclei reaction calculations is quantified in a model-independent framework. The analysis for neutron halos is extended to proton halo systems. The effective field theory results quantify which observable parameters of the strong interaction at low energy need to be determined more precisely for accurate cross-section calculations.

Advances in Predicting Continental Low Stratus with a Regional NWP Model

In the eastern Alpine region, subinversion cloudiness associated with elevated temperature inversions is a frequent phenomenon in autumn and winter, which often persists for several days. Although the prediction of fog and low stratus by numerical weather prediction (NWP) models has improved in recent years, these models still show deficiencies in the spatial and temporal evolution of such wintertime weather phenomena. In spite of sophisticated current assimilation schemes or simply due to unknown conditions, even the analysis shows large discrepancies compared to the true atmospheric state. Inversions are often “smeared out” and the moist layer below the inversion is too far from saturation. Model integration from such an initial state leads to strong biases in the total cloudiness and, due to erroneous radiative response, in 2-m temperature forecasts. In the present paper, an empirical enhancement scheme for subinversion cloudiness is introduced within the framework of Aire Limitée Adaptation Dynamique Développement International (ALADIN), the operational limited area model (LAM) at the Austrian Central Institute for Meteorology and Geodynamics (ZAMG). The scheme attempts to compensate for model deficiencies in the vertical temperature and humidity profiles in order to enhance or keep preexisting signals of inversions and associated low cloudiness. Thus, a positive feedback due to radiative reaction is activated, which finally leads to more realistic vertical profiles, low (and total) cloudiness, and improved 2-m temperature predictions. Case studies demonstrate the impacts of the scheme on predictions of the spatial distribution of low cloudiness and on the vertical profiles of temperature and humidity. Verification over stratus episodes within a 2-month period comparing a reference model run without the scheme with a modified model version with the subinversion cloudiness scheme confirms the ability of the scheme to improve stratus-related wintertime weather prediction.

Radiative reaction effect on electron dynamics in an ultra intense laser field

The radiative reaction effect of an electron is usually very small and can be neglected in most cases. But for an ultra intensity laser-electron interaction region, the radiation can become large. The influence of the radiative reaction effect of an electron interacting with an ultra intense laser pulses in vacuum on electron dynamics is investigated within the classical relativistic Lorentz-Dirac approach. A predictor-corrector method is proposed to numerically solve the equation of motion with the electron radiative reaction included. We study the counter-propagating case (for Thomson scattering scheme) and the same direction propagating cases (for laser acceleration). Our simulation results show that radiation can have great effect in the counter-propagating case. But in the vacuum laser electron acceleration regime, both the ponderomotive acceleration scenario case and the capture and acceleration scenario, radiative reaction effect can totally be ignored for laser intensity available presently or in the near-future.

Electromagnetic Radiation in Accelerator Physics

This article reviews some fundamental concepts and presents several recent techniques used for calculation of radiation in various environments. They include properties of longitudinal and transverse formation lengths of radiation, usage of the parabolic equation and the Kirchhoff diffraction integral in radiation, coherent radiation and fluctuations in the beam, and the radiative reaction force resulting from coherent radiation.