QGP effects in Ultra-High-Energy Cosmic Rays
IDPASC Portugal - PHD Programme 2019
2019 / 2020
Theoretical Particle Physics | Astroparticle Physics
Instituto Superior Técnico
Laboratório de Instrumentação e Física Experimental de Partículas
The Quark-Gluon Plasma (QGP) is a Quantum Chromodynamics state of matter characterized by extreme temperatures and densities. Currently produced in ultra-relativistic heavy-ion collisions, this strongly interacting medium is believed to be produced only in very dense/extended systems, such as Lead-Lead or Gold-Gold collisions. Recent results of high multiplicity proton-proton collisions at the LHC show strong collective effects whose magnitude is attributed to the presence of QGP droplets. These observations put to the test our understanding of the energy/density scale necessary to trigger QGP-like effects. Ultra-high energy cosmic rays (UHECRs) can be a unique opportunity to shed some light in this puzzle. With center-of-mass energies that can surpass 400 TeV, and with a hadronic nature that span elements from proton to iron, UHECRs can be used to explore the presence of QGP-like effects in a multitude of systems. The Pierre Auger Observatory, located in Argentina, is the largest experiment dedicated to the study of these extremely energetic cosmic rays. The results collected by Auger so far present several incongruences challenging to be explained within standard interactions and astrophysical scenarios, which significantly motivates the investigation of QGP effects at ultra-high-energy interactions. Hence, the candidate is expected to work on the interface between accelerator data (in particular LHC) and cosmic ray data (Auger) by investigating potential signatures of a strongly-coupled QCD medium in the development of UHRCRs. The work is expected to take place at LIP-Lisbon, within the Phenomenology and Auger groups.