The past two years have been rather exceptional for CERN: first in 2012, the CMS and ATLAS experiments discovered the Higgs boson, confirming the mechanism elaborated 48 years earlier by Robert Brout, François Englert and Peter Higgs. Then in 2013, Englert and Higgs received the Nobel Prize for Physics for their theory.
2014 is also going to be special year since CERN is going to turn 60. But beyond this anniversary, CERN is preparing the Large Hadron Collider (LHC) to explore new territories.
With the Higgs boson discovery, we have completed the Standard Model, the current theory that explains what makes all visible matter around us. But that is just a mere 5% of the total content of the Universe. The existence of dark matter tells us our current model is incomplete. So far, the various analyses of the data taken at 8 TeV has not yet revealed traces of dark matter or any new particles. To push all our searches further and faster, we need to increase the reach of the LHC by going to higher energies.
This is why since February last year all accelerators and experiments at CERN began a long shutdown for maintenance and consolidation. This will continue in 2014 for the LHC but many accelerators of CERN complex will be coming back to life starting this summer.
The starting point of the chain of accelerators is a simple hydrogen bottle. The electrons are stripped from the hydrogen atoms using an electric field to leave single protons. These are then accelerated in a small linear accelerator (LINAC 2 at the bottom centre of the diagram below). The Low Energy Ion Ring (LEIR) plays a similar role but with heavy ions.
The protons get an extra kick in the Booster before being injected into what is CERN’s oldest circular accelerator still in operation, the Proton Synchrotron (PS). Then the protons head for the Super Proton Synchrotron (SPS), where they reach 450 GeV in energy (that is 450 billion electronvolts). This is the final stage before injection into the LHC where the energy will get nearly thirty times larger, namely 13 TeV.
The beams from the accelerator chain are also delivered to various other experimental areas, such as ISOLDE and n-TOF where a huge number of experiments involving nuclei are conducted. Other protons hit a target to produce antiprotons for the Antiproton Decelerator (AD), a facility dedicated to antimatter studies. These experiments will all resume their activities in 2014.
All consolidation work for the LHC and its experiments will take place in parallel. ATLAS and CMS plan to complete all repairs and upgrades to their detector by November, ALICE at the beginning of December and LHCb in early January 2015.
Meanwhile, all physicists not involved with hardware are either completing the many ongoing analyses of all data taken up to 2013, preparing new simulations at higher energies, improving the data reconstruction algorithms or designing the new trigger selection criteria. Everybody is preparing to meet the challenge of dealing with more data at higher energy. All in the hope that we might be rewarded once more with new discoveries since there is still a whole new world to explore out there.
Pauline Gagnon
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