But recently scientists noticed that some pairs of particles were flying off from the collision point in correlated directions.
"Somehow they fly at the same direction even though it's not clear how they can communicate their direction with one another. That has surprised many people, including us," MIT physicist Gunther Roland, whose group led the analysis of the collision data along with Wei Liof Rice University, said in a statement.
A similar flight pattern is seen when two heavy particles, such as lead and lead, crash into each other. In this case, the collisions create what's called quark-gluon plasma -- a superhot soup of particles similar tothe state of the universe just after the Big Bang. This soup can sweep particles in the same direction, explaining why their flight directions would be correlated.
But quark-gluon plasma isn't possible with lead-proton collisions, like the ones in the new study. Now researchers think a different state of matter, the color-glass condensate, may act in a similar way. The color-glass condensate's dense swarm of gluons may also sweep particles off in the same direction, suggested Brookhaven National Laboratory physicist Raju Venugopalan, who first predicted the substance, which may also be seen after proton-proton collisions.