时间：2月14日（周五）下午16:00

　　地点：主楼C209会议室（视频）

　　报告人：Prof.Krzysztof Piotrzkowski（AGH University）

　　主持人:高杰研究员

　　报告题目：Bremsstrahlung (aka radiative Bhabha) at the CEPC: From beam lifetime limits to coherent beam-beam effects

　　报告摘要:

　　A good understanding of bremsstrahlung at high energy circular e+e- colliders is important as it might become the limiting factor for the beam lifetimes. In this talk, the impact of the so-called beam-size effects will be presented, in particular the strong apparent suppression of bremsstrahlung due to very small lateral beam sizes at the interaction points. The resulting beam lifetime limits will be discussed for all the CEPC collision energies and as a function of collision parameters. Finally, the effects of the coherent bremsstrahlung and validity of beamstrahlung calculations at the CEPC will be also discussed.

　　报告人简介:

　　Krzysztof Piotrzkowski, after defending his PhD thesis on the precise luminosity measurement in the ZEUS experiment, he mostly worked on the high energy photoproduction at HERA, first ever electron-proton collider. In total he spent almost 10 years at DESY in Hamburg, and then moved to CERN to work on the ATLAS experiment. In 2000 he moved to UCLouvain in Belgium and joined CMS where he pioneered novel studies of high energy photon-photon interactions at the LHC. During his career he initiated and worked on many developments of very forward near-beam detectors, in particular timing detectors with a picosecond resolution. In 2018 he left CMS and for two years joined the Virgo experiment, and afterwards got deeply involved in designing experiments at future electron-hadron colliders - the EIC at BNL and the LHeC at CERN. In 2022, after more than 30 years, he returned to Poland and joined Physics Faculty at theAGH Universitywhere he continues to work on the photon-photon physics and bremsstrahlung processes at the future electron-hadron colliders as well as on making the case of LHeC as the next big project at CERN. In 2023 he significantly extended the bremsstrahlung studies to include in this context also very interesting cases of the proposed circular e+e- colliders, and in 2024 he re-joined CMS.