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My Research

My collaborators and I work at an enormous and hugely powerful particle accelerator called the Large Hadron Collider (LHC). The machine is in a 17-mile long circular tunnel one hundred meters underground on the Swiss-French boarder near Geneva. It is the world's most powerful accelerator, producing collisions a million times more energetic than occur in the sun.

The extremely high energy is required to create very massive particles. This can be seen from Einstein's famous formula E=mc² which relates the energy of a collision with the mass of the particles it can produce. We hope to create some very heavy particles, a thousand times heavier than the proton and neutron which exist in normal matter.

These heavy-weight particles are thought to have been created in the very first fraction of a second after the big bang. Many would have lived a very brief existence before decaying. However if any of these particles were stable, they could survive to the current day, forming a sea of heavy particles everywhere around us. Such particles could very well be the explanation for the mysterious "dark matter", which has so far only made its presence known by the gravitational pull it exerts. If our theories about these new particles are correct, the LHC could be the first dark-matter factory on earth.

Careful measurements of the new particles will allow us to work out their relationship with the "ordinary" stuff which makes up people, planets and stars. It may turn out that the new particles are related to normal matter by a special kind of symmetry called supersymmetry. This discovery would mean that built into the very structure of space-time there is a special relationship between matter-like and force-like particles.

Another possibility is that the new heavy particles might be created by matter waves bouncing around in extra dimensions of space. The idea that the universe could contain more than three spatial dimensions is popular not only in science fiction, but is also predicted by many leading theoretical physicists. Since we can't see or move in them, any extra dimensions must either be curled up smaller than we can see, or they don't allow normal light and matter to pass into them.

At the moment we just don't know if either of these ideas is correct - this is leading-edge science, and the answers are not in the back of the book. Our current mathematical description of matter and forces, the "Standard Model" of particle physics, has been very well tested at the energies accessible to existing colliders, in some cases to extraordinary precision. However it may well be that when we get to these extremely high energies none of our ideas are right, and nature works in a way we haven't been able to predict.

The good news is that the LHC experiments can provide the answers to many of these questions. Our group is working on two areas. The first is making sure that the particles produced in the high energy collisions can be detected. The apparatus we're working on is a set of very sensitive silicon wafers, a bit like the chips which are used inside computers. These produce an electrical signal from which we can work out the position of any charged particles as they pass through. This information will then be combined with other measurements to reconstruct what happened in each collision.

The other thing we are researching is how best to measure the properties of any super-heavy particles we discover. Only a very small fraction of the collisions will produce such particles, so it is necessary to isolate those events, and study them in detail. The more careful we are in performing our measurements the more accurately we are able to work out what sort of particles they are - supersymmetric, extra-dimensional, or even something completely different.

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Representation of the ATLAS experiment underground near Geneva

Photograph of tha ATLAS experimental cavern during construction (2005)

Thermal image of the ATLAS semiconductor tracker barrel after assembly

Photograph of the ATLAS semiconductor tracker during its integration at CERN

Chart showing the approximate composition of the universe