Scientists from the Institute of Modern Physics (IMP) at the Chinese Academy of Sciences have made a breakthrough in understanding how the universe evolved just after the Big Bang.
In a new study published in Physics Letters B, they propose a new method for detecting an extraordinary state of matter called quark-gluon plasma (QGP), using “fingerprints” left by particles during high-energy collisions.
About 13.8 billion years ago, in the first tiny fraction of a second after the Big Bang, the universe was incredibly hot and dense.
During this time, instead of atoms like protons and neutrons, the universe was filled with free-moving quarks and gluons.
This special state is known as quark-gluon plasma. As the universe expanded and cooled, these particles combined to form the matter we see today.
Scientists have managed to recreate QGP in laboratories by smashing heavy atomic nuclei together at high speeds.
However, it has been very difficult to clearly track when and how QGP forms during these collisions. Professor Yong Gaochan from IMP explains that just like fingerprints can identify a person, the patterns in the types and amounts of particles produced in these collisions can reveal important clues about the formation of QGP.
Using an advanced simulation method called the multi-phase transport model, the research team studied the collisions of different heavy ions, including calcium-40, calcium-48, and gold-197.
They focused on four types of particles: Λ hyperons, K+ mesons, π mesons, and protons. When comparing lighter elements like calcium to heavier ones like gold, they noticed unusual changes in how many of each particle were produced.
Their findings suggest that by carefully measuring how many identical particles are emitted in different collision setups, scientists can detect the formation of QGP.
In particular, when QGP forms, the free movement of quarks and gluons prevents too many particles from colliding and producing new ones, leading to lower particle counts than expected. Without QGP, particles keep colliding and produce higher yields.
To confirm their results, the team tested their idea using another simulation model and found consistent evidence linking these unusual particle ratios to the creation of quark-gluon plasma. The new method also reduces errors and uncertainties that have made detecting QGP difficult in the past.
Professor Yong said the new discovery brings scientists one step closer to mapping the full phase diagram of matter under extreme conditions and offers new ways to explore how the early universe evolved.
