The world’s most powerful accelerator, the 27 km long Large Hadron Collider (LHC) operating at CERN in Geneva established collisions between lead nuclei, this morning, at the highest energies ever. The LHC has been colliding protons at record high energy since the summer, but now the time has now come to collide large nuclei (nuclei of lead, Pb, consist of 208 neutrons and protons). The experiments aim at understanding and studying the properties of strongly interacting systems at high densities and thus the state of matter of the Universe shortly after the Big Bang.
The equipment at the LHC was readied for the new collisions on November 17th, but yesterday scientists confirmed that they’d created stable beams that were ready for use in experiments. Now, all four of the LHC’s detectors will take part in analyzing what happens when lead ions slam into each other.
Colliding lead ions—the normal metal atoms, just stripped of electrons—isn’t a new idea. When they collide, they create a quark and gluon plasma that resembles the kind of matter that would have been present just after the Big Bang. But colliding them at the kinds of energies that the LHC can now achieve—where temperatures are set to reach several trillion degrees—will allow the physicists to see a greater volume than ever of the matter.
“The collision energy between two nuclei reaches 1000 TeV. This energy is that of a bumblebee hitting us on the cheek on a summer day. But the energy is concentrated in a volume that is approximately 10-27 (a billion-billion-billion) times smaller. The energy concentration (density) is therefore tremendous and has never been realised before under terrestrial conditions,” explains Jens Jørgen Gaardhøje, professor at the Niels Bohr Institute at the University of Copenhagen and head of the Danish research group within the ALICE experiment at CERN.
In a press release, Paolo Giubellino from the LHC explained what the scientists are eager to learn about when they look at it:
“There are many very dense and very hot questions to be addressed with the ion run for which our experiment was specifically designed and further improved during the shutdown. For instance, we are eager to learn how the increase in energy will affect charmonium production, and to probe heavy flavour and jet quenching with higher statistics. The whole collaboration is enthusiastically preparing for a new journey of discovery.”
Just exactly what the the researchers will find out, then, remains somewhat of a mystery. But, like some of the quarks that the researchers will be studying,therein lies the charm.