Scientists at CERN have produced tiny droplets of a state of matter thought to have existed right at the birth of the universe, after slamming particles together at high energy in the Large Hadron Collider (LHC).
Researchers at the University of Kansas working with an international team at the LHC produced quark-gluon plasma with fewer particles than previously thought possible.
The material was discovered by colliding protons with lead nuclei at high energy inside the supercollider's Compact Muon Solenoid detector. Physicists have dubbed the resulting plasma the "littlest liquid."
"Before the CMS experimental results, it had been thought the medium created in a proton on lead collisions would be too small to create a quark-gluon plasma," said Quan Wang, a KU postdoctoral researcher working with the team at CERN.
"Indeed, these collisions were being studied as a reference for collisions of two lead nuclei to explore the non-quark-gluon-plasma aspects of the collisions," Wang said.
"The analysis presented in this paper indicates, contrary to expectations, a quark-gluon plasma can be created in very asymmetric proton on lead collisions," he said.
The unexpected discovery was said by senior scientists associated with the CMS detector to shed new light on high-energy physics.
"This is the first paper that clearly shows multiple particles are correlated to each other in proton-lead collisions, similar to what is observed in lead-lead collisions where quark gluon plasma is produced," said Yen-Jie Lee, assistant professor of physics at Massachusetts Institute of Technology (MIT).
"This is probably the first evidence that the smallest droplet of quark gluon plasma is produced in proton-lead collisions," said Lee, co-convener of the CMS heavy-ion physics group.
Researchers described quark-gluon plasma as a very hot and dense state of matter of unbound quarks and gluons - that is, not contained within individual nucleons.
"It's believed to correspond to the state of the universe shortly after the Big Bang," Wang said.
"The interaction between partons - quarks and gluons - within the quark-gluon plasma is strong, which distinguishes the quark-gluon plasma from a gaseous state where one expects little interaction among the constituent particles," he said.
While high-energy particle physics often focuses on detection of subatomic particles, such as Higgs Boson, the new quark-gluon-plasma research instead examines behaviour of a volume of such particles.
Wang said such experiments might help scientists to better understand cosmic conditions in the instant following the Big Bang.
"While we believe the state of the universe about a microsecond after the Big Bang consisted of a quark-gluon plasma, there is still much that we don't fully understand about the properties of quark-gluon plasma," he said.
The research was published in the journal APS Physics.
