Exploring the God Particle

If the God Particle is real, 2012 will be the year of its discovery. Scientists at CERN have been searching for proof of the existence Higgs boson since 2008, when the construction of the Large Hadron Collider finally came to an end. Now, after four years, the LHC – a 27-kilometre ring of superconducting magnets located in Geneva, Switzerland – is ready to take up a new challenge. On 13 February, CERN announced that in the next year the Collider will fire proton rays at an energy of 4 TeV. Until now, the LHC has run at a beam energy of ‘only’ 1.18 TeV (Physics fun fact: 1TeV is about the kinetic energy of a flying mosquito). Up until 2009, the highest energy used for this kind of experiment was less than 1 TeV; this record was held by the Tevatron accelerator at the Fermi Laboratory in Illinois, USA.

So far, researchers have been hesitant to boost up the working energy of the LHC, even though the system is meant to sustain collisions of protons up to 14 TeV. The major quench incident that occurred in 2008, just a few months after the inauguration, showed that extreme care is needed when dealing with such highly energetic particles. In that case, faulty connection between magnets caused six tons of liquid helium to be dispersed in the tunnel. This caused heavy damage to the instrumentation, forcing CERN to stop the experiment for several weeks. Money and time were wasted, and people’s safety threatened.

Moreover, in March 2010, the new research program officially started with a 7 TeV proton collision (3.5 TeV per beam), causing mass panic around the world and rumors of a possible catastrophe. Despite the general fear, the LHC has been functioning as smoothly as ever. However, the potential risks of these experiments are not to be ignored.

In the press release following the announcement, CERN’s Director for Accelerators and Technology Steve Myers said: “When we started operating the LHC for physics in 2010, we chose the lowest safe beam energy consistent with the physics we wanted to do. Two good years of operational experience with beam and many additional measurements made during 2011 give us the confidence to safely move up a notch, and thereby extend the physics reach of the experiments.”

Myers also mentioned that the LHC will undergo a long shutdown at the end of the year. During this 20-months break, new technology and improvements will be implemented, so that in 2015 the collider will be able to work at the maximum energy of 7 TeV per beam. However, Research Director Sergio Bertolucci believes that it is likely that major results will already be seen by the end of the year. “By the time the LHC goes into its first long stop at the end of this year, we will either know that a Higgs particle exists or have ruled out the existence of a Standard Model Higgs,” he claims in the press release. “Either would be a major advance in our exploration of nature, bringing us closer to understanding how the fundamental particles acquire their mass, and marking the beginning of a new chapter in particle physics.”

The Higgs boson is often referred to as the “God Particle” because of its central importance in modern particle physics. According to the Standard Model – the currently most accepted theory on interactions between particles and forces – its existence is necessary to explain why all the other particles have most of their mass. Its discovery would therefore constitute a major step forward towards a better understanding of how the laws governing our Universe work.

The LHC is the main contributor of data regarding the Higgs boson, and the announcement strengthened the already widely held feeling that we are now closer to finding this particle than we have ever been before. The results produced by ATLAS and CMS, the two main experiments looking for the Higgs at CERN in the past few years, allowed physicists to narrow down the hypothetical mass of the Higgs to a window of merely 16 GeV. This mass is now thought to be around 124-126 GeV.

However, for the results to be considered a real discovery a year’s worth of consistent observations are needed. Statistically speaking, particle physics has a well defined definition of ‘discovery’: data must have a five-sigma (or five standard deviations) level of certainty. This is simply a scale of how unlikely it is that the results are only a product of chance rather than an actual effect of a physical phenomenon. In a nutshell, a three-sigma level would represent the same likelihood as tossing a coin eight times and getting eight heads; five-sigma would correspond to getting 20 heads in a row.

This step up in energy is great news for the scientific community. It is in everyone’s interest that the LHC continues to fulfill its task and help us unravel the beautiful mathematics that regulates our Universe. In the eventuality that the Higgs boson is not discovered, our current theories will have to be completely revised and researchers would have to face whole new challenges.