Things that go bump in the night

Cern's 27km-long underground Collider may lead particle physicists to the 'theory of everything'. But before that, they must educate a wide-eyed public in the basics of science. Matthew Reisz reports

September 4, 2008

In Dan Brown's thriller Angels and Demons, an evil genius steals a canister containing a quarter of a gram of antimatter, hides it under Vatican City and threatens to unleash its devastating power. The theft takes place at Cern (an acronym formed from the original name of the Organisation Europeen pour la Recherche Nucleaire).

A film, starring Tom Hanks, is due for release next year. As the hype began to build, the world's largest physics laboratory has received a number of inquiries about the science behind the plot. Yes, in theory, say the experts at Cern, it is possible. One could build a bomb in that way. There is just one tiny problem.

It would take a couple of billion years to produce enough antimatter to make a bomb the size of an "ordinary" hydrogen bomb, and there are thousands of those in the world already. So perhaps this is one nightmare scenario we don't need to worry about.

Cern's Large Hadron Collider (LHC), initially mooted in the 1980s, finally goes live next week. The eight sections of the km (16.7 mile) underground "ring" (or circular tube) have now been cooled with superfluid helium to temperatures within 1.9 degrees of absolute zero, and protons will soon be sent in both directions to stage collisions.

It is hard not to talk in superlatives. Phrases such as "the most ambitious experiment ever", "the largest magnet in the world", "the most complicated piece of apparatus science has ever seen", "unlocking the secrets of the universe", "recreating conditions a fraction of a billionth of a second after the Big Bang" are bandied about. And for once, provided we don't expect results by the end of the month (see box, page 38), the hype - around the science, at least - seems to be justified.

Most surreal and mind-boggling of all is Cern's straight-faced health and safety announcement, which came in the form of a press release reassuring us that the experiments pose no risks.

Concerns have apparently been expressed about cosmic rays, microscopic black holes, "strangelets" ("hypothetical lump[s] of 'strange matter' containing almost equal numbers of particles called up, down and strange quarks") and "dangerous proton-eating magnetic monopoles".

Others have speculated "that the universe is not in its most stable configuration, and that perturbations caused by the LHC could tip it into a more stable state, called a vacuum bubble, in which we could not exist".

But we need not live in fear of any such apocalyptic outcomes, according to Cern. They may sound as bizarre as anything dreamed up by Dan Brown, but fortunately there is nothing to get alarmed about, since "whatever the LHC will do, nature has already done many times over during the lifetime of the Earth and other astronomical bodies".

The dizzying physics has been celebrated with the appropriately mad idea of getting a group of dancing scientists and engineers to perform an LHC rap. Acclaimed as "the best supercollider rap ever", it can easily be found on the internet.

Cern also employs some highly enthusiastic and articulate theoretical physicists such as John Ellis with a rare gift for giving non-specialists a taste of what is at stake.

Current thinking is based around the so-called Standard Model, formulated by Steven Weinberh, Abdus Salam and Sheldon Glashow in the 1960s, which unifies three of the four fundamental forces of nature (the electromagnetic, strong and weak interactions).

The discovery of so-called W and Z particles in 1983 at Cern confirmed essential elements of the Standard Model. But the theory also requires the existence of the Higgs Particle (or Boson), postulated in 1964 by Peter Higgs, emeritus professor at the University of Edinburgh - though not a single one has yet been "spotted" (see box, right).

"It's like a room without windows," explains Ellis. "We can't see what lies beyond it. The Higgs Boson is the door which completes the room and provides access to what is outside. It would complete the Standard Model - without that additional ingredient it leads into inconsistencies."

One of the main tasks of the LHC is to track down what has been described as "the most sought-after particle in modern physics" (or something performing a similar function).

This, of course, is easier said than done. Ellis reckons that a Higgs Boson will turn up "once in a trillion events" and that it will then "decay very rapidly into things like the results of the normal muck produced in collisions".

Then there are other celebrated puzzles on which Cern hopes to shed light. We don't know why - unfortunately for the world's evil geniuses - there is far, far less antimatter in existence than matter, although the answer, hopes Ellis, might explain "how things unfolded just after the Big Bang".

We have not yet integrated gravity with the other three fundamental forces or unravelled the strange mystery of dark matter. As there are not enough "regular particles" around to stop galaxies flying apart, some kind of additional invisible mass must be holding them together.

Since such dark matter is invisible, Ellis admits it is a bit like "the dog that didn't bark", which can be detected only indirectly in the form of missing energy. However, he believes that this will be in exactly the right "range" to be picked up by the LHC.

Detectors have been specially designed "to pick up the most interesting new physics - heavy unseen particles which soon decay and convert mass into energy. We are looking for energetic stuff coming off at large angles to the beam."

Some of the outstanding puzzles led theoretical physicists such as Julius Wess and Bruno Zumino, also partly based at Cern, to develop the theory of supersymmetry in the 1970s.

Ellis hopes that the data produced by the LHC may lead to a new synthesis that "kills three birds with one supersymmetric stone and amounts to a significant augmentation of the Standard Model", although it may also require "a whole shitload of additional particles". Nobody ever said fundamental physics was going to be easy.

Investigating such uncharted territory has required Cern to take its game to a whole new level. The underground circuit has been in place since the 1980s, when it was used to house the Large Electron-Positron Collider (LEP), the predecessor of the LHC. This ceased operation in 2000, but it used to produce 10 collisions a second, so it was possible to store the data on every single one.

The LHC may eventually produce around 1 billion proton collisions per second. Two of the key challenges are sifting out the unusual occurrences from the background noise and generating enough computing power to analyse the mountains of information. The plan is to reduce the 40 million images generated every second to just a few hundred within 3 microseconds and then send them out to researchers all over the world.

There are eight access points to the circuit and several of them house "experiments" or detectors which are assembling all these data.

The Compact Muon Solenoid (CMS), for example, brings together a team of 2,000 scientists from all over the world under the leadership of Professor Tejinder S. Virdee of Imperial College London, who expects to devote two thirds of his working life to the project.

The detector is built in a huge new cavern whose construction was delayed by the discovery of an underground river. It was assembled in 15 huge pieces in a building on the surface (soon to be dismantled to give local villagers a better view of the Alps).

Some pieces weigh up to 2,000 tonnes, meaning that they had to be lowered into the cavern with the kind of crane used in shipyards. The five coil modules were transported from Genoa to Marseille by sea, taken up the River Rhone and then carried by truck to Cern. The outer diameter of 7.2m was chosen so that the mission could be accomplished without widening any roads or pulling down bridges.

Before Dan Brown and the current excitement about the LHC, Cern was probably most famous as the place where Tim Berners-Lee developed the idea of the World Wide Web. When it was realised that the data being generated by the new collider would fill a 20km pile of CDs each year and require the capacity of 100,000 computers, it was decided that these should not all be located on site.

Although Cern has a number of eerie, temperature-controlled rooms housing 10,000 interlinked, blinking hard drives, the rest of what is needed is provided by an unprecedentedly large and distributed grid of computers all over the world belonging to organisations that form part of the EGEE (Enabling Grids for E-sciencE) consortium.

New technology, which has acquired the name "middleware", provides the essential tools to access spare data and processing power from the scattered computers.

With few security issues (who, except a physicist, can understand the data from a proton collision?), open access and ownership of intellectual property rights by the whole consortium, some are already predicting that the Grid may represent the next step beyond the Web. In the words of a recent Cern publication: "New dimensions of space exist - in theory. New dimensions of cyberspace are now a reality."


Matt Rooney writes: When it is "switched on" next week, the Large Hadron Collider (LHC) will smash protons together at almost the speed of light in order to gain a greater understanding of the universe. In this artificial recreation of the Big Bang, mini black holes will be created, extra dimensions discovered and the origin of mass at last known.

Hopefully. Contrary to stories in the media, many of these discoveries will take years or may never occur. Why? Because particle accelerators take years to "ramp up" to full power and to iron out all the engineering problems. Even when the machine is working at full capacity, it may take years to sift through and interpret the enormous amount of data from the detectors.

It is therefore necessary to clear up a common misconception. Scientists do not "switch on" particle accelerators as we do a lamp. It has taken months of careful testing to coax the first few protons around the "ring" and may take years to increase incrementally the number of circulating and colliding particles.

There is good reason for this slow pace. First, if the LHC beam at full power was misdirected by, for example, a failure of one of the steering magnets, it would annihilate anything in its path - imagine shooting a delicate piece of scientific equipment with a really big laser gun. What is more, a powerful proton beam will have a tendency to make the accelerator components slightly radioactive over time - more so in the event of a missteered beam.

So the beam wants to be very weak in the beginning. Then, if something breaks - a common occurrence in the early stages of an accelerator operation - someone can go in and fix it without the danger of coming out with a luminous green glow. After a certain time, maintenance will have to be done remotely - perhaps with expensive robots - or the broken components will have to be left to "cool down" and become less radioactive.

Then there is the issue of statistical uncertainty. Although the LHC sends billions of particles flying towards one another, they are so small that the chance of collisions occurring is very slim.

A primary motivation behind the LHC is to discover the Higgs Particle - the so-called God Particle. This was proposed by Scottish physicist Peter Higgs, who suggested that all atoms in the universe derive their mass through interaction with the Higgs Field.

It is hoped that confirmation of the existence of the Higgs Particle at the LHC, along with many other discoveries, will bring us closer to a Grand Unified Theory of Physics, or a Theory of Everything. This is the greatest pursuit in physics and a challenge that has been the ambition of Einstein and Hawking - an explanation of the workings of the universe that tells us how everything interacts, from the forces that bind atoms together to the way the planets orbit the sun.

But Professor Higgs will almost certainly not win his Nobel prize this year. The Higgs Particle, if it exists, will be produced and detected in very small quantities. To generate enough data to be certain of its existence will take years. This is why the expected lifetime of the LHC is at least 15 years.

So, yes, the LHC is one of the truly great international endeavours of our time - a "cathedral" of science. It is likely to shine a light on the origins of the universe and spark the dawning of a new golden age in particle physics. But please be patient with the physicists, everyone. The revelations will not be obvious from day one. It takes time to understand "the mind of God".

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