Seminario

Il giorno 9 aprile alle ore 15 presso la stanza 412, Pavel Jucha (Krakow and Ferrara Universities) terra' un seminario dal titolo

In the quest of the nature of Light-by-light scattering

Abstract

With the development of quantum physics, scientists realized that light quanta should interact with each other. This realization led to calculating the theoretical cross section value for this process in the 1930s, which laid the groundwork for quantum field theory [1]. Almost 90 years later, we found the experimental evidence of light-by-light scattering [2]. The strong electromagnetic fields interacting in ultraperipheral heavy-ion collisions (UPC) allow us to observe such subtle processes. However, the story has not ended yet. The contemporary detectors measure cross section with the high di-photon mass and photon transverse momentum threshold. Beyond these limits, we expect more events of light-by-light scattering. In the low-pt region, we also await observation of different scattering mechanisms: light meson resonances and photon scattering described by VDM-Regge theory [3].

During my talk, I will explain the theoretical background of UPC and the mechanisms of light-by- light scattering. I will compare the theoretical results with data obtained by ATLAS [4] and CMS [5] experiments since the discovery report in 2017. I will also show the predictions for future measurement possible due to ALICE detector upgrades planned for the 2030s [6].
[1] K. Scharnhorst, arXiv:1711.05194 (2023).
[2] ATLAS Collaboration (M. Aaboud et al.), Nature Phys., 13852 (2017).
[3] P. Jucha, M. Kłusek-Gawenda, A. Szczurek, Phys. Rev. D, 109, 014004 (2024).
[4] ATLAS Collaboration (G. Aad et al.), Phys. Rev. Lett., 123(5):052001 (2019).
[5] CMS Collaboration (A. M. Sirunyan), Phys. Lett. B, 797:134826 (2019).
[6] ALICE Collaboration, CERN-LHCC-2022-009, LHCC-I-038, arXiv:2211.02491 (2022).