After 20 years of preparation the biggest experiment on Earth is ready to begin<em> - News</em>

By Danielle Reeves
Wednesday 10 September 2008

Physics researchers from Imperial College London are today gearing up to start taking data and recording results in the biggest experiment on earth, which will recreate local conditions similar to those that existed in the earliest instants of the universe, a split-second after the Big Bang.

After over 20 years of design, development and construction, the Large Hadron Collider (LHC) particle accelerator, a 17-mile long circular tube 100 metres below the French-Swiss countryside at CERN, is due to be switched on today. This means a beam of protons will be sent many times round its entire length for the first time.

Once fully activated, the LHC will smash the protons together at very high energies to create new particles – some of which have been theorised but never seen before, including perhaps the elusive Higgs-Boson, the particle which scientists believe gives mass to other particles.

As well as the hunt for the Higgs boson, the scientists working at CERN hope that data from the LHC will also help to solve some of the biggest mysteries of the universe, including the nature of dark matter, the number of space dimensions in which we live, and more.

A large cohort of Imperial physicists are based at CERN, working with colleagues from around the world on the massive particle detectors that will record the results of the high energy collisions. The last few months have seen preparations for the LHC start-up step up a gear, with important testing being carried out on the detectors before the particle beams are switched on.

Claire Timlin, an Imperial postgraduate student who has been working on the Compact Muon Solenoid (CMS) detector for three and a half years, explains: "Once the LHC is functioning and whilst the particle collisions are taking place, we cannot enter the underground cavern containing the CMS detector due to radiation from particles emerging from the collisions. Also, accessing many elements inside the detector requires it to be opened, a procedure which can take a number of weeks.

"So we have been thoroughly testing all the complex elements of the detector, and then testing them again, to make sure they're ready for action when the collisions begin – we don't want to waste a second of data from the LHC!"

In the last few months researchers have been testing the detectors in preparation for today's start-up

Imperial's Dr Matt Ryan, whose eight years of work on the CMS detector has been focused on the electromagnetic calorimeter – the part of the detector that measures the energy of photons and electrons - describes the atmosphere at CERN over the last few months:

"It's very exciting to see everything coming together after such a long time planning, designing and constructing the LHC and the four detectors stationed along the its 17-mile length. It's been a privilege to get the chance to work with physicists, engineers and technicians from all around the world to put an enormous project like this together," he said.

Professor Geoff Hall, an Imperial researcher who also works on the CMS experiment, has been closely involved with preparing the tracker detector for today's start-up date. The tracker will measure the trajectories of particles as they emerge from high energy collisions at the heart of the detector. It is, Professor Hall explains, perhaps the most complex part of the whole CMS detector: "It will generate the most data and be subject to the highest levels of radiation," he says.

Since June this year, the tracker has been almost fully operational, and Geoff and his colleagues have been doing practice runs, testing the tracker by using it to detect muons passing through it – tiny invisible particles that make up harmless cosmic rays that are constantly striking the Earth.

"Our cosmic ray tests have shown us that the tracker is working very well", said Professor Hall, "We're all very excited by the capabilities of this experiment, and of the LHC accelerator itself."

Imperial's Professor Tejinder Virdee is the lead scientist on the massive CMS particle detector experiment

Imperial's Professor Tejinder Virdee is the lead scientist on the CMS experiment, and has been working towards today's historic start-up event for over 20 years. He explained the significance of today's event, saying:

"The LHC will let us collide particles at higher energies than ever before, creating conditions which haven't existed since just after the Big Bang. Effectively, our experiments here will let us look back in time to the infancy of the universe – we have some predictions about what we will find, but the most exciting thing about this experiment is that we may find things we have not foreseen. All expectations are that what we will find at the LHC will re-write the textbooks."

One of the other four detector experiments at the LHC is also being led by an Imperial researcher. Professor Andrei Golutvin is the spokesperson for the LHCb experiment, a detector smaller than the CMS, and designed specifically to study the balance of matter and antimatter in the universe.

Professor Golutvin explains: "When the universe began with a Big Bang, equal quantities of matter and antimatter were created. However, almost immediately afterwards, nearly all the antimatter disappeared, leaving matter to form everything in the universe from stars and planets to life on Earth. We hope the LHCb experiment will enable us to learn more about the subtle differences between matter and antimatter because these differences could explain why, since the Big Bang, nature has favoured matter over anti-matter."

Over all project leader for the Large Hadron Collider is Lyn Evans, a Visiting Professor at Imperial. Describing recent preparations for the LHC start-up he said: "We're finishing a marathon with a sprint. It's been a long haul and we're all eager to get the LHC research programme underway."

Professor Jordan Nash, head of the high energy physics research group at Imperial, said: "An opportunity to take such a big step in scientific understanding comes along only rarely. It's brilliant that so many Imperial scientists, from PhD students to professors, have had the opportunity to play key roles in the development of one of the most important and ambitious scientific experiments ever carried out. We are all extremely excited about beginning to see data collected with the particle detectors, and look forward to producing some extremely important results in the coming months and years."

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