The Large Hadron Collider has restarted after a two-year break for a major refit and has begun to circle protons around its 27km tunnel for the first time since 2013. Particle beams have been sent in both directions along parallel pipes just under the speed of light.
Actual collisions aren’t due to start for around another month but when they do, it will be at almost twice the energy involved in previous tests allowing scientists to hopefully glance new physics beyond the Standard Model.
Record levels
Rolf Heuer, director general of Cern, the operator of the LHC told engineers and scientists gathered in the lab that now the ‘hard work starts’ while director for accelerators and technology Frederick Bordy added that after two years work, the LHC was in great shape.
The next step is to see the energy of the beams created in the collider reach record new levels. There had been a slight delay after an electrical fault had caused a week’s hold-up on the restart.
At first, the protons are injected at a low energy but over the coming months, the plans are to increase the beam’s energy to 13 trillion electronvolts, almost double what the collider had operated at during its first run.
Start up
At 8:30am engineers started to thread the proton beam through each of the sections of the huge circle, one at a time, before completing a number of full terms. Once this was complete, a second beam was started, running in parallel.
The teams watching the experiments have already detected ‘splashes’ of particles when a stray proton hits one of the shutters used to keep the beams running along a certain path. When this happens near an experiment, detectors can even pick up some of the debris from these collisions.
Standard model
Physicists are frustrated by the Standard Model of particle physics as it describes 17 subatomic particles, including 12 building blocks of matter and 5 ‘force carriers’ of which the last, the Higgs boson, was finally detected in 2012 by the LHC.
One of the four big experiments that the LHC will be working on will involve slamming protons together and quantifying the fallout. They are hoping that a number of the most baffling elements of the universe can be explained beyond the Standard Model, properties that have been theorised but not yet proven.
Top on the list is dark energy, the all-pervading force that is believed to account for the expansion of the universe and its increase. Dark matter is also thought to be the web that holds everything visible together and would explain why galaxies spin quicker than they should do, based on our observations.
Debris from these tiny impacts could contain everything from new particles to the telltale gaps that show dark matter is present to even hidden dimensions. The first new collisions at full speed should begin in May.
