In the first microseconds after the Big Bang, the universe was filled with quark-gluon plasma, an extremely hot soup of quarks and gluons. Physicists on the CMS experiment at CERN’s Large Hadron Collider, with a team led by researchers at MIT and including Vanderbilt University’s Yi Chen group, recreated tiny drops of it by smashing heavy atomic nuclei together. They looked for events where a quark shot through the plasma opposite a Z boson. The Z boson barely interacts with the plasma, so it acted as a marker. Out of about 13 billion collisions, they found around 2,000 usable events and mapped the energy patterns in the plasma.
What they saw looked like a wake, with splashes and swirls like a duck paddling across water. The team says it’s the first direct evidence that the plasma responds to a fast-moving particle as one connected fluid. The results were published in Physics Letters B.
Why it matters: The wakes carry information about what the plasma is like, which gives physicists a way to study matter as it was in the first moments of the universe.