Angular Correlations of Particle Momentum in the Hot Dense Medium

The early universe consists of element particles such as quarks and gluons after the big bang. Understanding their interactions is crucial for the physics, especially their interaction strength: do they behave like a gas or like water? A lot of experiments and theoretical calculations have been performed in labs, using different particles to study the properties of the early universe. Luckily, scientists can create this state of matter on earth by proton-proton collisions (or nucleus-nucleus collisions). As this matter produced in the particle collisions last only a very short of time ~ fm/c where c is the speed of light. How to probe this medium becomes difficult? This work suggests that people can study the momentum correlations between particles moving in the opposite direction in the hot medium. If the early universe is a STRONGLY coupled medium, then the medium will change both particles’ momentum. After they move out of the hot medium, their momentum angular is NOT pi anymore. In summary, the hot medium random interactions will change the momentum angular between two particles even their initial momentum is in the opposite direction. This work employs the Langevin equation to simulate their evolutions in the hot medium, and get good results.