Proton collisions at the Large Hadron Collider – what’s in it for you?

The most expensive and advanced scientific instrument in human history is aiming to revolutionise our understanding of the universe. Ransom Stephen explains what precisely is happening and what outcomes can be expected
Ransom Stephens
31 March 2010

In the shadows of the Jura Mountains protons are being accelerated to the highest energies ever produced by human beings. Deep underground, in the Large Hadron Collider at CERN, the European Center for Particle Physics, which straddles the Swiss-French border near Geneva, a beam of protons are colliding head-on with other protons at the record setting 7 trillion electron-volts (TeV). It’s a process that has been described as akin to smashing fine watches together to determine what makes them tick.

Taxpayers from the UK to Australia, Japan to Germany, China to Canada, Italy to Estonia, Vietnam to the United States who have invested over 10 billion Euro into the machine may reasonably ask: What do I get?

The expectations are clear if arcane.

What we can expect of these experiments, ATLAS (the contrived acronym for A Torioidal LHC ApparatuS) and CMS (Compact Muon Solenoid) at one collision point  a couple miles around the beampipe’s arc, is a great deal of new information about the universe.

The Holy Grail of the experiments is to either discover the long-sought Higgs boson or demonstrate unequivocally that the Higgs does not exist. The Higgs, which was called “The God Particle” by Nobel Laureate Leon Lederman, is a particle that was proposed by Scottish physicist Peter Higgs to answer the question: how do particles obtain mass. It’s an esoteric sounding question, but to push the frontier of human understanding farther, it must be answered. You see, in the Standard Model of Particle Physics – a model that encompasses everything experimentally verified about the basic building blocks of nature – there is no good “reason” for particles to have mass, but they obviously do. Every theory of how stuff works at the most fundamental level is predicated on this annoyingly successful model. The masses of particles don’t emerge from the theory in a satisfying burst of understanding, they have to be measured and installed by hand.

Mass is a measure of the inertia of an object. The heavier it is, the harder it is to turn or accelerate. The Higgs mechanism describes a field of particles, not unlike the gravitational fields that permeate space near things like stars and planets, that saturates the universe and constantly interacts with particles in a way that slows them down, imposing inertia on them. If the Higgs is not observed at the LHC then it will be eliminated from play and the field will take a different, potentially even more interesting direction.

Discovery or elimination of the Higgs will take a while. ATLAS collaborator and Louisiana Tech Physics Professor H. Lee Sawyer says that the LHC will run at 7 TeV for one year or until a certain amount of data (called “an inverse femtobarn, fb-1,”) is acquired, whichever comes first. The accelerator will then be upgraded to double the energy. The reason that ever higher energies are necessary is that there is an inverse relationship between the observable size of an object and the energy with which they are probed. The previously most powerful particle collider, the TeVatron at Fermilab, which is located in a prairie in the western Chicago suburbs, collides protons with antiprotons, the antimatter equivalents of protons, at about 2 TeV.

A long list of other measurements will be made with data acquired at the LHC. Point-like objects called quarks and leptons will be analyzed with ever greater precision, casting light on our understanding of the nature of force and matter, the formation of the universe, and the very geometry of spacetime. Evidence for new and old theories alike may be uncovered, quarks and leptons may turn out to be composed of still smaller building blocks, tiny blackholes could conceivable form and illuminate the troublesome nature of quantum gravity, but back to that most basic taxpayer question: What do I get?

The problem with trying to pose an answer is not simply that “I don’t know” but that whatever I can think of probably won’t be as spectacular as what we will get.

It’s fun to speculate on how engineers will someday convert the science into technology; a super-duper rocket propulsion system for touring the solar system, new techniques for generating power, ways to encode data within the nucleus of an atom so that all the computing power now on earth could be built on the head of a pin, but history shows that our guesses won’t come close to living up to the reality, when it finally comes.

No one could predict the utility of health diagnostic tools like X-ray photography or nuclear Magnetic Resonance Imaging (MRI) as the phenomena were discovered in the basic science labs of their times. You might have guessed that the circuitry and software techniques developed for experiments would someday make their way into consumer products like radios and disk drives, but you might not have foreseen the digital camera or, for that matter, the iPod.

In the 1980s, as it was being developed at CERN atop the existing internet infrastructure for the purpose of easing software and data distribution to collaborating experimentalists, no one foresaw the impact that the World Wide Web would have on the world’s economy.

I can’t tell you exactly what you’ll get for your money, but I can tell you what won’t happen at the LHC: A black hole will not form and swallow the planet and all of us.

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