When heavy ions (the nuclei of heavy atoms such as gold and lead) collide at high energies at Brookhaven National Laboratory’s Relativistic Heavy Ion Collider (RHIC) and Europe’s Large Hadron Collider (LHC), the components of the nuclei (protons and neutrons) melt to form a hot soup of their constituent particles, quarks and gluons. A new model that accurately describes the experimentally observed patterns of particles flowing out from this “quark-gluon plasma” (QGP) suggests that the effective shear viscosity, or resistance to flow, is close to the ideal limit used to define a “perfect” fluid.
“Our result is consistent across finer and finer detailed analyses of particle flow patterns,” said Bjoern Schenke, a Goldhaber Fellow in the nuclear theory group at Brookhaven Lab and a coauthor on a paper describing the analyses in Physical Review Letters published earlier this year.
“These findings help answer the question of how ‘perfect’ the perfect liquid QGP created at RHIC is—that is, how close the viscosity comes to a limit derived from quantum mechanics—and how this property varies with temperature. Our findings indicate that viscosity increases away from the ideal limit with the increasing temperatures reached at LHC,” Schenke said.
The findings will also help scientists better understand how the internal characteristics of the heavy ions before they collide—particularly dense concentrations of gluons known as color glass condensate—shape the initial collision geometry and rapidly turn into the liquid quark-gluon plasma.
Read more at: Phys.org