Large hadron collider: A revamp that could revolutionise physics

Scientists are excited deep in the Alps.

They whisper about the changes that would be made to our understanding of the Universe.

Dr SamHarper has been searching for the fifth force for as long as he has been a particle physicist.

For the past 20 years, Sam has been trying to find evidence of a fifth force of nature, with gravity, electromagnetism, and two nuclear forces being the four that physicists already know about.

He is pinning his hopes on a major change to the Large Hadron collider. It is the world's most advanced particle accelerator, a vast machine that smashes atoms together to break them apart and discover what is inside them.

In a three-year upgrade, it has been souped up even more. Its instruments are more sensitive, allowing researchers to study the collision of particles from the inside of atoms in higher definition; its software has been enhanced so that it is able to take data at a rate of 30 million times each second; and its beams are narrower, which greatly increases the number of

This means that the best chance of finding new particles in the LHC is now. The hope is that it will make discoveries that will lead to the biggest revolution in physics in a hundred years.

Researchers hope to find evidence of Dark Matter, an invisible substance that makes up most of the Universe.

The researchers are under pressure to deliver. The expectation was that the LHC would find evidence of a new realm of physics by now.

The European Organisation for Nuclear Research, also known as Cern, is located on the Swiss-French border. Blocks of 1950s office buildings and dormitories sprawl across a two and a half square mile site of manicured lawns and winding roads named after revered physicists.

It is 100 metres underground. One of the biggest discoveries of our generation was made by one of the giant detectors at the heart of the LHC, and it was the particle known as the Higgs Boson. The detector is long and high. It is one of the four instruments used to analyse the particles created by the LHC.

It is 7,000 tons of metal, electronics, and wiring. It is a thing of great beauty and it is being used by one of the scientists.

Marcella tells me about the improvements to the detector during the three-year shutdown of the LHC.

She tells me that the experiment will be able to detect, collect and analyse data two to three times better.

I find it hard to imagine that something so large is needed to detect particles that are many times smaller than an atom.

Each of the four detectors is doing a different experiment. It is in the center of the detectors that the particles known as protons are crashed together after being accelerated close to the speed of light.

Smaller particles fly off in different directions after the collision. The path and energy of the particle are tracked by the detector systems, but it is the trail that tells the scientists what kind of particle it is.

Most of the smaller particles are known to science. Physicists here are looking for evidence of new particles, which are rare and may arise from the collisions.

Physicists believe undiscovered particles hold the key to a new view of the Universe. The biggest shift in physics thinking would be created by their discovery.

The past three years have seen engineers upgrade the LHC to produce more collisions. The refurbished machine has a better chance of finding new particles. Much of that work has been led by Dr Rhodri Jones.

I meet Rhodri in the magnet assembly area, which is similar to an aircraft hangar. The 15 metres long cylindrical magnets that bend the particle beams around the accelerator are being reworked. There is no margin for error in this work.

The team made the beams narrower so that more particles could be squeezed into a smaller area. This increases the chance of particles hitting each other.

He says that the greater the number of collisions, the greater the chance of actually finding what is going on and seeing small anomalies.

The improvement in the beam means that we will be able to get the same amount of collisions in the next three years as we did in the past.

The data from the collisions has been captured and processed in a big way. Each of the four detectors is collecting data at a rate of 30 million times a second. It's too much for a human mind to take in, but any one of the collisions may contain the crucial piece of evidence of the existence of one of the new particles the scientists are searching for.

The latest artificial intelligence techniques have been used to upgrade the software that searches through all the data collected and identifies and saves the readings that might be of interest to the scientists.

The Standard Model is the current theory of physics. The theory has been brilliant at explaining how the particles come together to create atoms which make up the world around us. The Standard Model explains how the particles interact with nature, such as electromagnetism and the nuclear forces that hold the components of atoms together.

The Standard Model cannot explain how gravity works or how invisible parts of the Universe behave. 95 per cent of the Universe is made up of invisible particles and forces from the movement of galaxies in space. No one has been able to determine what they are.

These particles might explain how the vast majority of the universe works. Dr Bona tells me that there is hope for that.

She beams, "It is a really exciting time, we have worked for the past three years updating the machinery." We are ready now.

From the moment I met her, she was passionate. I asked her if the discovery of a dark matter particle would be one of the biggest discoveries in physics.

She laughs, eyes widening, and says that it would be incredible to see that happen in the coming months.

The scientist who has spent the last two decades hunting for the fifth force of nature is excited. At the other end of the Cern complex, he works at one of the four detectors called the CMS.

There are hints of that fifth force in the results from several other particle accelerators around the world. Sam tells me that his quest may be over with the extra power of the LHC.

The excitement in his voice builds as he says out loud what cannot be said in scientific circles until there is evidence.

This would change the field. It would be the biggest discovery in particle physics in a long time.

Sam is struggling to find words.

It will be bigger than the Higgs.

The tenth anniversary of the discovery of the Higgs Boson will be celebrated later this year. The festivities draw attention to the fact that the publicly funded 3.6 billion-pound LHC hasn't made a really big discovery since it was built. Many had hoped that the most powerful particle accelerator would discover dark energy, a fifth force or some other paradigm-changing particle by now.

There is a lot riding on the results the researchers get over the next few years because Cern will soon be putting forward proposals for an even larger hadron collider. The FCC would have a ring of 60 miles that would go under the lake.

The FCC could cost 20 billion dollars. The current machine has at least another ten years to go, and several more upgrades that will give it even more oomph with which to try to discover the particles that will forever change physics. The scientific leaders at Cern will be presenting their case for the next phase of particle physics experiments soon. If the latest upgrade fails to find the new particles in the next two to three years, it will be hard for the governments of member nations to commit to a big increase in funding.

Dr SamHarper admits to feeling a little bit terrified as the LHC embark on its next set of experiments.

We are desperately trying to get everything together and we are working hard to make sure we don't miss any new physics. The new physics will be the worst thing in the world because we don't find it.

There is intense excitement about what the next few years hold.

The thing that drives all particle physicists is that we want to discover the unknown and this is why things like the fifth force and dark matter are so exciting because we have no idea what it could be or if it exists.

The Standard Model may have been the first crack discovered by researchers at the US equivalent of the LHC. The current theory of how the Universe works will need to be torn apart to make way for a new, unified and more complete theory.