The project Initial Conditions for Quark and Gluon Matter Formation at the LHC (InitialConditions) addresses a central open question in nuclear and particle physics: how the structure and shape of atomic nuclei determine the initial conditions that lead to the formation of quark–gluon plasma (QGP) in ultrarelativistic heavy-ion collisions. Understanding these conditions is essential for interpreting the collective behavior of strongly interacting matter and for linking the fundamental theory of quantum chromodynamics (QCD) to emergent macroscopic phenomena in nuclear systems.
At the Large Hadron Collider (LHC), collisions between heavy nuclei such as lead or xenon recreate, for a fleeting moment, the extreme environment that existed microseconds after the Big Bang. The properties of the resulting QGP depend sensitively on the geometry, density, and fluctuations of the colliding nuclei at the instant of impact. Yet, despite decades of progress, the precise mapping between nuclear structure and the observed collective flow remains poorly constrained. Traditional techniques struggle to disentangle the initial geometry from the subsequent dynamical evolution, limiting our ability to extract quantitative information on nuclear shape and deformation.
This ERC Starting Grant project was conceived to overcome these limitations by developing a new generation of analysis tools capable of probing the initial conditions of heavy-ion collisions with unprecedented precision. Its core objective is to establish robust, model-independent observables that directly connect measurable multi-particle correlations—such as cumulants of transverse momentum and flow coefficients—to the fluctuations in the initial energy density and geometry of the collision system.
The project aims to:
1. Develop and validate a cumulant-based methodology for multi-particle transverse momentum and flow correlations that isolates genuine collective effects from non-flow backgrounds.
2. Apply these tools to high-statistics ALICE data to extract, for the first time, nuclear deformation and shape transitions at ultrarelativistic energies.
3. Explore light-ion collisions (O–O and Ne–Ne) as a new testing ground for QGP formation, establishing a unified framework for small and large nuclear systems.
The new methodologies have already enabled the discovery of a nuclear shape-phase transition in xenon collisions at the LHC—the first direct experimental evidence that nuclear geometry leaves measurable imprints on QGP flow. By integrating advanced statistical, Monte Carlo, and hydrodynamic techniques, the project bridges particle physics, nuclear structure, and computational science. Ultimately, InitialConditions strengthens Europe’s leadership in precision QCD studies and sets new standards for imaging nuclear geometry and the collective behavior of primordial matter.
