Black holes and the God particle

The Large Hadron Collider may revolutionise our understanding of nature, from tiny atoms to the entire universe, writes Marie-Catherine Mousseau

Black Holes, the Hadron Collider and the God Particle’ was the title of a talk given by Dr Cormac O’Raifeartaigh in Trinity in June, organised by Astronomy Ireland. The previous week had seen the very first official conference on results from the Large Hadron Collider (LHC).

There is an enduring, appealing mystery associated with the terms ‘black holes’ and ‘God particle’. “A lot of physicists might have a problem with the populist title,” Dr O’Raifeartaigh admitted. The lecturer in physics at Waterford Institute of Technology went on to explain why there are proper scientific concepts behind the sexy words.

Black holes and the God particle have been both associated with the LHC. But these are far from being the only issues, challenges and hopes underlying the world’s biggest accelerator.

The LHC is a gigantic scientific instrument at the CERN (European Organization for Nuclear Research) near Geneva, a 27-kilometre circular tunnel running at about 100 metres underground. While the technology used is cutting edge, the principle is simple: two beams of subatomic particles called ‘hadrons’ – either protons or lead ions – travel in opposite directions and collide head-on (with 600 M collisions/sec) at very high energy.

Though Dr O’Raifeartaigh noted that the energy itself (14 TeV or 2.2 µJ) is not that huge (it would be equivalent of the energy of a fly running into a wall), what is huge is the energy density: the amount of energy is colossal compared to the microscopic space which contains it.

The particles created in such collisions are then analysed by teams of physicists from around the world using four special detectors.

The early universe
As Dr O’Raifeartaigh pointed out, the purpose of the LHC is twofold: first, the exploration of the fundamental constituents of matter, the building blocks of all things, and the forces that hold these particles together. Second, the study of the early universe. He explained that the LHC represents the highest energy density generated since the Big Bang (the only higher energies that we know of are those produced by cosmic rays). As such, it re-creates the conditions just after the Big Bang.

As summarised on the CERN website, ‘The LHC will revolutionise our understanding, from the minuscule world deep within atoms to the vastness of the universe.’ But what about black holes and the God particle?

Black hole controversy
Black holes were associated with the LHC in what is known as ‘the black hole controversy’. Basically, it has been said that the Collider would create black holes big enough to swallow the earth.

“One doesn’t expect to create a black hole at the LHC,” the physicist reassured the audience. This is mainly due to the most famous equation E =mc2. Since m = E/c2 and c is the velocity of light (a very large quantity), one gets only a minute amount of mass m from a very large amount of energy E.

This does not fit the characteristics of a black hole, which by definition is an area with an extremely high gravitational field.
What is more, cosmic rays bombarding the earth’s atmosphere create collisions of energy far higher than the LHC, without creating black holes.

Even though the LHC is only able to produce a tiny amount of mass, it has the potential to achieve a breakthrough in our understanding of what mass is. This is where the God particle comes into play. Mass is usually defined by its effect, which includes the inertia of an object and its influence in a gravitational field. But according to the Standard Model – the model describing all the particles and forces that constitute matter – there is a particle responsible for the mass of other particles. This particle is what is referred to as the God particle, or Higgs boson (because was first theorised in 1964 by the British physicist Peter Higgs).

“I happen to be one of the few physicists who like the name God particle for the Higgs boson,” Dr O’Raifeartaigh commented. “It was probably originally ‘that goddamn particle’ due to its elusiveness, but I think ‘God particle’ neatly gets across its importance. After all, it’s the interaction of the other particles with the Higgs field that’s thought to determine their mass, according to the Standard Model.”
The God particle is the only Standard Model particle that has not been observed experimentally, and physicists are very hopeful it will be produced by the LHC. They even have a pretty good idea at which energy levels to find it.

If they do find it there, it will validate the Standard Model describing matter as we currently understand it. If they do not find it there, it might mean that it does not exist, in which case a whole realm of physics would have to be revised.

Antimatter and dark matter
However, the God particle is far from being the only fundamental discovery that could be made thanks to the LHC. Antimatter, dark matter and supersymmetry, to name just a few, are all mysteries on which the LHC has the potential to shed light, thus improving our understanding of the universe.

LHC experiments
Antimatter is of particular interest to Dr O’Raifeartaigh. One of the LHC experiments, which is happening at the LHCb detector, is designed to solve the problem of the matter/antimatter imbalance. Each known particle of matter is thought to have originally had an equivalent antiparticle of opposite charge.

When a matter particle meets an antimatter particle, they annihilate one another. This means that, for the universe to exist, an imbalance between matter and antimatter must have occurred – so that some matter was left over after everything else had been annihilated.

The fundamental question is: why is there something, rather than nothing? To answer that, physicists at the LHCb are searching for asymmetries in matter/antimatter decay. “The LHCb experiment is of particular interest to an Irish audience, as a group at University College Dublin (www.ucd.ie/physics/lhcb) is heavily involved, despite Ireland’s non-membership of CERN,” Dr O’Raifeartaigh pointed out.

There is another huge unsolved question that occupies the mind of cosmologists. What are the particles accounting for dark matter, an invisible substance that is supposed to make up some 22 per cent of our universe? Standard matter, as we know it, only makes 4 per cent, while the rest is devoted to an even more mysterious and hypothetical player – dark energy.

Some may be a bit suspicious of a model that accounts for only 4 per cent of what we see. However, the physics lecturer is not too surprised about the invisibility of most things: “There’s no reason why all matter should be visible.”

Again, the Collider might provide us with an answer. Dark matter could take the form of a particle called neutralino, belonging to a hypothetical class of fundamental particles called ‘supersymmetry particles’, which could be detected by the LHC. For the first time, dark matter could be observed directly – not through its indirect effects on surrounding matter.

Supersymmetry and TOE
Supersymmetry particles could also be a key player in our understanding of the universe. If observed, they might help us come up with a unified theory, an extension of the Standard Model – the holy grail of physicists.

According to the Standard Model, the universe is made of four forces. Two of them, the electro-magnetic force (holding atoms together) and the weak force (beta decay) have been unified. But scientists are always looking for more simplicity. Expanding the model by unifying the strong force (holding nucleus together) to this electro-weak force would lead to the GUT – Grand Unified Theory.

Physicists then had to find an even more encompassing name for the theory unifying these three forces to the remaining fourth force, gravity. The name they came up with is nothing less than TOE – the Theory Of Everything.

Supersymmetry particles
Would the LHC help achieve this ultimate goal? It might, if it manages to observe the hypothetical supersymmetry particles. Fundamental particles that form matter are called ‘fermions’, while the fundamental particles associated with the four forces are called ‘bosons’. SUSY, or supersymmety theory, states that each fermion (particle of matter) is associated with a boson (particle of force), its SUSY particle.

According to physicists, if SUSY is correct, it would improve GUT and make TOE possible.

All this potential for discovery is definitely exciting, but according to Dr O’Raifeartaigh, there is more to be excited about with regard to the LHC. Things that the LHC has already achieved are equally impressive, even though they did not generate media hype.

Atomic theory
He reminded us that it took centuries for humanity to discover what matter is made of. Even in antiquity, Democritus had hypothesised the existence of insecable units of matter (atomic theory), the buildings blocks of everything, but it was not until 1909 that atoms were observed. And we had not reached the fundamental units yet.

The irreducibly minimal quantity of matter as we understand it now – called the quarks (a name taken from a sentence of the book Finnegan’s Wake by James Joyce) – were hypothetised in the 1960s and observed in the 1970s.

“So, in the space of a few months, all four detectors at the LHC have been busily rediscovering the elementary particles of the Standard Model that took so many years to first detect,” Dr O’Raifeartaigh enthused, also regretting the lack of media attention.

The Collider has done even more to support modern physics than rediscovering all fundamental particles. He added that what occurs in the CERN on a regular basis is a “supporting evidence for our underlying theories of modern physics”.

Particles in the LHC, which travel at around 99.99 per cent of the speed of light, keep showing that Einstein was right with his theory of relativity. According to this theory, the more one approaches the speed of light, the heavier the particle gets and the more time contracts. “This is what we observe all the time in the LHC,” he said.

Increasing mass is the reason why we can never reach the speed of light (the energy required would be infinite). But time contraction could have more interesting applications. If, like those little protons, we were travelling in a train going around the earth at a speed very close to the speed of light, time contraction would mean that 100 years on earth could be one week for us.

Getting off that train one century later, we would travel in time…towards the future.

To keep up with the LHC, follow the particle physics blogs at: www.interactions.org/cms/?pid=1025915.
See Dr Cormac O’Raifeartaigh’s ‘Antimatter’ blog: http://coraifeartaigh.wordpress.com/

l Marie-Catherine Mousseau holds a PhD in Neurosciences and is Editor of MIMS Ireland.

l The views expressed above are those solely of the author and in no way may be deemed to reflect the views or policy of MSD Science Centre or MSD.