According to the ALICE collaboration at LHC (CERN), certain rare proton collisions have properties that are similar to those of a quark–gluon plasma. In the past, these properties had been observed for collisions of heavy nuclei only. The physicists are now confronted with a new enigma: how can a state of quark–gluon plasma emerge in a system as "small" as that generated by a collision between two protons?
During a collision of atomic nuclei, the formation of quark-gluon plasma is usually signaled by an increase in the production of hadrons (composite particles) containing at least one so-called "strange" quark. Some of the proton collisions at the LHC producing the largest number of particles were found to have this signature.
This unexpected result has considerable implications for physicists. It opens the possibility for them to study the quark–gluon plasma in a new light. This will give them a chance to better understand the properties of the strong interaction that gives rise to the confinement of quarks and gluons within the hadrons.
This work was carried out based on collisions of 7 TeV protons during the LHC's first operating period.
Contact: Alberto Baldisseri