A researcher Heikki Mäntysaari from the University of Jyväskylä (Finland), has been part of an international research group that has made significant advances in modeling heavy ion collisions. New computer models provide additional information about the matter in the early universe and improve our understanding of the extremely hot and dense nuclear matter.

When atomic nuclei collide at near light speed, they form a new state of matter where quarks and gluons are liberated from protons and neutrons. To study this matter, called a quark–gluon plasma (QGP), scientists need to understand the initial conditions, including the shape and energy density of the created matter.

Quark-gluon plasma tells the story of the early universe

The University of Jyväskylä has participated in international research that has improved computer models that simulate these initial conditions along with the entire collision dynamics. Researchers solved equations that describe how the internal structure of the colliding protons and nuclei changes with collision energy. The updated models match patterns of particles produced by the collisions better than older ones, giving a clearer view of the QGP’s birth.

- This research helps reveal how nuclear matter behaves under extreme conditions, like those that existed just after the Big Bang. By making models of these collisions more accurate, we can better measure the properties of the QGP, says Associate Professor Heikki Mäntysaari from the University of Jyväskylä, who participated in the research.

Research is moving forward with experimental and theoretical collaboration

The new models better correspond to experimental measurements made at Brookhaven National Laboratory (BNL) and the European Organization for Nuclear Research (CERN).

- By connecting experimental results with theoretical advances, the study opens the door to more precise extraction of quark–gluon plasma properties, improving our understanding of matter under extreme conditions. We are also eagerly waiting for the new Electron-Ion Collider which will start to operate at Brookhaven in 2030s, providing complementary measurements, explains Mäntysaari.

Jyväskylä's quark research on the international forefront

The University of Jyväskylä is home to a world-class the Centre of Excellence in Quark Matter funded by the Research Council of Finland. The ultimate goal is to understand one of the four fundamental forces of nature: the strong interaction between the fundamental building blocks of ordinary matter, quarks and gluons.

- International research collaboration is crucial, especially when combining experimental and theoretical knowledge. Experiments are becoming increasingly complex, which is why it is more important than ever that all parties understand what is being measured and how phenomena are modeled theoretically. This is also the main motivation behind our Centre of Excellence: it brings together theorists and experimentalists performing measurements at CERN. This shared understanding is key to advancing the field, points Mäntysaari.

The Research Council of Finland and the European Research Council (ERC) supported this research.