Exploring Quark-Gluon Plasma effects in the forward region
PT-CERN Call 2022/2
Instituto Superior Técnico (Universidade de Lisboa)
Laboratório de Instrumentação e Física Experimental de Partículas
Ultra-High Energy Cosmic Rays interact with the Earth’s atmosphere producing Extensive Air Showers (EAS) at very high energies, which are not accessible at the Large Hadron Collider (LHC). The number of muons at the ground, measured by ground-based experiments like the Pierre Auger Observatory, is a key-observable to infer the mass composition of cosmic rays. However, LHC-tuned hadronic interaction model simulations, like EPOS-LHC, have been consistently predicting a lower muon production than the data obtained from measurements of EAS. This long-lasting problem is known as the Muon Puzzle and it shows itself for center-of-mass energies greater than 8 TeV, which is still within the reach of the LHC. The formation of Quark-Gluon Plasma (QGP) in the first interaction of EAS has been proposed as a possible solution and has led to the development EPOS-QGP, a new purely phenomenological hadronic interaction model that accounts for more visible QGP effects than its predecessor EPOS-LHC. The goal of this research work is to study the possible behavior of QGP in the forward region and in small systems, assessing if it can be formed in EAS and explain the Muon Puzzle, by further studying this new promising model. After determining its key-parameters for QGP formation and assessing their impact on air showers and on macroscopic collision parameters, the model shall be confronted with LHC and Auger data, especially from the p-O and O-O collisions of Run 3 and from the AugerPrime upgrade. Focus will be given to the EAS muon distributions, which have been shown to be sensitive to the different shower energy scales, with the model being tested both at LHC energies and higher, reaching a center-of-mass energy of about 400 TeV. This work will limit the future findings of the next hadronic accelerator, the Future Circular Collider, while it paves the way for the study of hadronic physics in air showers, improving our understanding of the Universe and of the Standard Model.