QCD & QGP at the LHC & Prospects with heavy ions with LHCb detector

par M. Gines MARTINEZ (Subatech CNRS/IN2P3 - IMT Atlantique - Nantes Universite)

vendredi 24 avr. 2026, 14:30 → 15:30 Europe/Paris

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Quantum Chromodynamics (QCD), the theory of the strong interaction, is a beautiful theory based on the fundamental SU(3) interaction between quarks (as fermions) and gluons (as exchange bosons). However, its predictive power and precision are strongly limited by confinement. Even in the asymptotic sector, a precision of better than 10% is difficult to achieve, since the initial and final state ingredients always remain non-perturbative. Experimentally, the strong interaction has been studied via its bound states, known as hadrons, and their lifetimes and decay channels.

Over the last 15 years, significant progress has been made with the discovery of exotic hadrons — hadrons containing more than three quarks. The structure of hadrons, mainly protons and neutrons, is studied through lepton-hadron interactions. A new area of research will be explored with the new Electron Ion Collider at high centre-of-mass energy, using polarised proton and electron beams. Hadron-hadron interactions are mostly non-perturbative processes that can be viewed, at RHIC and LHC energies as the interaction of two high-density gluon clouds. In these collisions, many fundamental interactions take place coherently and incoherently in parallel, making them more difficult to calculate using ab initio QCD theory. At sufficiently high multiplicity, the high particle density resulting from the collision allows for a hydrodynamic description of the QCD matter, which is expected to deconfine above a certain temperature threshold. As a by-product, heavy ion collisions at ultra-relativistic energies provide the most intense high-energy photon beams which can be used to explore the structure of the proton and nucleus, and even to image peripheral heavy ion collisions thanks to the coherent production of quarkonia in photon-nucleus interactions. The LHCb detector is well suited to addressing all these phenomenological studies of QCD physics, including exotic hadrons, fixed target experiments, probing the quark-gluon plasma with heavy flavour production, photon-nucleus interactions and the study of nuclear structure in colliding nuclei. Last but not least, the LHCb upgrade for Run 5 will increase the instantaneous luminosity at the LHCb interaction point by a factor of 10, enabling the reconstruction of the most central Pb-Pb collisions.