The Large Hadron Collider at the European Organization for Nuclear Research (CERN) near Geneva, Switzerland, enters a new phase of operations Nov. 4. Scientists will stop running streams of protons through the machine and begin running lead atoms, stripped of their electrons, around the ring so that they smash into each other.

Physicists from the Heavy Ion Group at the UC Davis physics department are part of the team for the lead ion experiments. The group includes Professors Daniel Cebra and Manuel Calderon de la Barca, postdoctoral scholar Sevil Salur and graduate student Jorge Robles. Salur and Robles are currently at CERN.

The record-setting energies available for heavy ion collisions at the Hadron collider will yield large numbers of rare and heavy particles, Cebra said. Those particles will be used to study quark-gluon plasma, which is what the universe was made of in the first instants after the big bang. Study of the particles will also help scientists understand how the plasma evolved into the kind of matter the universe is made of today.

By measuring the tracks of the different particles produced in the quark-gluon plasma, the researchers will be able to learn about the plasma's properties and about the fundamental forces acting on the particles that travel through it, Cebra said.

The Large Hadron Collider is being used by physicists to study the fundamental building blocks of nature. Experiments to date have already charted new territory, according to CERN. Advances so far include validation of aspects of the Standard Model of particles and forces at these new high energies; observations of the "top quark," a particle whose existence was first confirmed at FermiLab in Batavia, Ill.; and limits set on the production of certain new particles, for example “excited” quarks.

Thousands of physicists from around the world, including many from UC Davis, are working on the vast project in teams. The UC Davis Heavy Ion Group is working on muon triggers, highly sensitive detectors that will record the presence of pairs of positive and negative muon particles that form from the decay of other particles.

The collider will use lead ions until Dec. 6, when operations will pause for maintenance. Operation of the collider will start again in February, and physics experiments will continue through 2011.