CERN begins LHC upgrade

Following the discovery of what appears to be the Higgs boson CERN's Large Hadron Collider has been shut down so that it can be upgraded. If all goes well, the upgrades will almost double the power of the LHC, enabling the particle accelerator to carry out the second part of its primary mission: proving or discovering the existence of super symmetry.

Higgs boson

The Higgs boson or Higgs particle is an elementary particle initially theorised in 1964, and tentatively confirmed to exist on 14 March 2013.The discovery has been called "monumental"because it appears to confirm the existence of the Higgs field,which is pivotal to the Standard Model and other theories within particle physics. In this discipline, it explains why some fundamental particles have mass when the symmetries controlling their interactions should require them to be massless, and—linked to this—why the weak force has a much shorter range than the electromagnetic force. Its existence and knowledge of its exact properties are expected to impact scientific knowledge across a range of fields, and should eventually allow physicists to determine whether the final unproven piece of the Standard Model or a competing theory is more likely to be correct, guide other theories and discoveries in particle physics, and—as with other fundamental discoveries of the past—potentially over time lead to developments in "new" physics, and new technologies.

This unanswered question in fundamental physics is of such importance that it led to a search of over 40 years for the Higgs boson and finally the construction of one of the most expensive and complex experimental facilities to date, the Large Hadron Collider, able to create and study Higgs bosons and related questions. On 4 July 2012, a previously unknown particle with a mass between 125 and 127 GeV/c2 was announced as being detected, which physicists suspected at the time to be the Higgs boson. By March 2013, the particle had been proven to behave, interact and decay in many of the expected ways predicted by the Standard Model, and was also tentatively confirmed to have + parity and zero spin, two fundamental criteria of a Higgs boson, making it also the first known scalar particle to be discovered in nature, although a number of other properties were not fully proven and some partial results do not yet precisely match those expected; in some cases data is also still awaited or being analyzed. As of March 2013 it is still uncertain whether its properties (when eventually known) will exactly match the predictions of the Standard Model, or whether additional Higgs bosons exist as predicted by some theories.

The Higgs boson is named after Peter Higgs, one of six physicists who, in 1964, proposed the mechanism that suggested the existence of such particle. Although Higgs' name has become ubiquitous in this theory, the resulting electroweak model (the final outcome) involved several researchers between about 1960 and 1972, who each independently developed different parts. In mainstream media the Higgs boson is often referred to as the "God particle," from a 1993 book on the topic; the sobriquet is strongly disliked by many physicists, who regard it as inappropriate sensationalism.

In the Standard Model, the Higgs particle is a boson with no spin, electric charge, or color charge. It is also very unstable, decaying into other particles almost immediately. It is a quantum excitation of one of the four components of the Higgs field, constituting a scalar field, with two neutral and two electrically charged components, and forms a complex doublet of the weak isospin SU(2) symmetry. The field has a "Mexican hat" shaped potential with nonzero strength everywhere (including otherwise empty space) which in its vacuum state breaks the weak isospin symmetry of the electroweak interaction. When this happens, three components of the Higgs field are "absorbed" by the SU(2) and U(1) gauge bosons (the "Higgs mechanism") to become the longitudinal components of the now-massive W and Z bosons of the weak force. The remaining electrically neutral component separately couples to other particles known as fermions (via Yukawa couplings), causing these to acquire mass as well. Some versions of the theory predict more than one kind of Higgs fields and bosons. Alternative "Higgsless" models would have been considered if the Higgs boson were not discovered.

In particle physics, elementary particles and forces give rise to the world around us. Nowadays, physicists explain the behaviour of these particles and how they interact using the Standard Model—a widely accepted and "remarkably" accurate framework based on gauge invariance and symmetries, believed to explain almost everything in the world we see, other than gravity.

But by around 1960 all attempts to create a gauge invariant theory for two of the four fundamental forces had consistently failed at one crucial point: although gauge invariance seemed extremely important, including it seemed to make any theory of electromagnetism and the weak force go haywire, by demanding that either many particles with mass were massless or that non-existent forces and massless particles had to exist. Scientists had no idea how to get past this point.

Work done on superconductivity and "broken" symmetries around 1960 led physicist Philip Anderson to suggest in 1962 a new kind of solution that might hold the key. In 1964 a theory was created by 3 different groups of researchers, that showed the problems could be resolved if an unusual kind of field existed throughout the universe. It would cause existing particles to acquire mass instead of new massless particles being formed. By 1972 it had been developed into a comprehensive theory and proved capable of giving "sensible" results. Although there was not yet any proof of such a field, calculations consistently gave answers and predictions that were confirmed by experiments, including very accurate predictions of several other particles, so scientists began to believe this might be true and to search for proof whether or not a Higgs field exists in nature.

If this field did exist, this would be a monumental discovery for science and human knowledge, and is expected to open doorways to new knowledge in many fields. If not, then other more complicated theories would need to be explored. The easiest proof whether or not the field existed was by searching for a new kind of particle it would have to give off, known as "Higgs bosons" or the "Higgs particle" (after Peter Higgs who first predicted them in 1964). These would be extremely difficult to find, so it was only many years later that experimental technology became sophisticated enough to answer the question.

While several symmetries in nature are spontaneously broken through a form of the Higgs mechanism, in the context of the Standard Model the term "Higgs mechanism" almost always means symmetry breaking of the electroweak field. It is considered proven, but the exact cause has been exceedingly difficult to prove. The Higgs boson's existence would finally after 50 years confirm that the Standard Model is essentially correct and allow further development, while its non-existence would confirm that other theories are needed instead.

The LHC consists of a ring tunnel that is 27 km or 17 miles long in circumference and 175 meters or 574 ft. below the surface at the French-Swiss border near Geneva. Inside the tunnel are two beam lines and each of the beam lines carry a proton beam that travels in opposite directions around the ring. The beams intersect at four positions where the proton beams are smashed together, producing oodles of data that is then analyzed by the ATLAS and CMS particle detectors. Depending on the strength of the beams, different kinds of collisions occur, and different subatomic particles are produced. 

The proton beams are kept on their circular path with the help of 1,624 superconductiong electromagnets, most of which wigh more than 27 tones. The magnets, which are made of niobium-titanium, are kept at -271,25 C or 1.9 K with the help of 96 tons of liquid helium. The LHC is the largest cryogenic facility in the world.

Up until its planned shutdown, each of LCH’s proton beams had an energy of 4 TeV (teraelectronvolts), resulting in a total collision energy of 8 TeV. After the upgrade, each beam will operate at 6.5 TeV, for combined collision energy of 13 TeV- more than six times the power of any previous particle accelerator. To achieve this upgrade CERN is replacing 10,000 connections, installing 5,000 insulation systems, and performing 10,170 leak tests, and 18,000 electrical tests. Some of the magnets will also be tested or replaced. In total, the upgrade will cost approximately $105 million, and should be completed by early 2015.

Some critics claim that CERN is throwing good money after bad, as this upgrade is actually more of a repair. The original LHC design spec, as it was completed in 2008, should’ve been capable of 7 TeV proton beams (14 TeV collisions). Due to an accident just after it was turned on, though, an electrical fault led to six tonnes of liquid helium exploding into the tunnels, causing significant damage and an extensive repair period. In the four years since, the physicists haven’t taken the beams past 4 TeV, for fear of blowing another gasket.

Having found a Higgs boson (not necessarily the Higgs boson), though — one of the LHC’s primary goals — it is now a lot easier for CERN to justify the long shutdown. In essence, when the LHC switches back on in 2015, it will finally be performing at a level that should’ve been possible back in 2008.

With the LHC at full power, the scientific community will try to confirm that they have actually found the Higgs boson, and after that they will continue the search for proof of supersymmetry — the particle accelerator’s other primary goal. ”The LHC is more than just a one trick pony,” ATLAS project leader Pippa Wells tells the BBC. “It wasn’t designed to find just the Higgs. We hope to find something completely new that will change our understanding of the Universe. We are on the threshold of finding many more new particles.” In essence, supersymmetry is a theory that postulates that there are a lot more particles out there, in the TeV energy range, that would fill in some of the gaps left by the Standard Model. In the supersymmetrical version of the Standard Model we would need to double the number of elementary particles, as none of the existing particles (gluons, photons, electrons, etc.) could be superpartners of each other.So far, going by observations made in late 2012, it doesn’t look very good for supersymmetry — but really, that’s what makes the LHC so darn exciting: Not even the world’s most eminent particle physicists have any idea what the Large Hadron Collider will find at higher energy levels.