LHCb first results from proton-lead run

At the "Workshop on proton-nucleus collisions at the LHC" in Trento, Italy, the LHCb collaboration discussed first results from the proton-lead run

The LHCb Collaboration has just presented at the Workshop on proton-nucleus collisions at the LHC, Trento, Italy, the first results from the analysis of proton with lead ion collision run data taken in January-February 2013. Already these first results made an important contribution to the understanding of heavy ion collisions.

In the Standard Model of Cosmology quarks and gluons were freely moving in a state called a quark-gluon plasma until < 10-5seconds after the Big Bang. As the Universe cooled, they became confined inside protons and neutrons. The theory of quark-gluon interactions, the strong force interaction theory, QCD, predicts that the state of quark-gluon plasma can also exists in high temperature matter created by high energy collisions between large atomic nuclei, called by physicists heavy ion collisions. But how to prove that the quark-gluon plasma is really formed? A reduced rate of J/ψ particle production in heavy ion collisions was considered as a "smoking gun" argument in favour of quark-gluon plasma formation by physicists analysing results of measurements performed in the CERN Super Proton Synchrotron (SPS) after 1986 and more recently in the Brookhaven RHICcollider. Profound analysis has shown, however, that reality is more complicated. In some models, for example, the J/ψ particle could also be regenerated in nuclear matter, partons (quark, gluons) could be saturated and/or lose energy, etc. in normal (so called cold) nuclear matter.

Data recording collisions of protons with lead ions were collected in the LHC experiments in January-February this year. In such collisions, formation of a quark-gluon plasma is not expected, and therefore measurements based on these data allow the study of interactions in cold nuclear matter. The analysis of J/ψ production was of particular interest.

Read more on the LHCb public website