Lead–proton collisions produce unexpected form of matter

MIT News : Collisions between protons and lead ions at CERN’s Large Hadron Collider may have produced a form of matter called a color-glass condensate, which is a liquid-like wave of gluon plasma. In 2 million collisions seen by the LHC’s Compact Muon Solenoid (CMS), some of the resulting particles exhibited behavior that suggested they were entangled. A normal particle collision results in an explosion of particles. But in the leadâproton collisions, some pairs of exploded particles followed matching paths, meaning each particle communicated its direction to the other via entanglement. Gunther Roland of MIT, who led the group analyzing the CMS data, had seen similar shared-path behavior in protonâproton collisions and the collisions of nuclei of heavy elements such as lead and gold. Heavy nuclei collisions produce a quarkâgluon plasma, and protonâproton collisions are believed to create a color-glass condensate. Both plasmas sweep up the entangled particles and push them down identical paths. Roland said that the color-glass condensate had not been expected in the leadâproton collisions, which were being done to establish a point of reference for leadâlead collisions. Roland’s group plans additional collisions to try to determine if the color-glass condensate is the cause of the entangled behavior.