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Dr Victoria Martin

Dr. Victoria Martin completed both her undergraduate and postgraduate studies at the University of Edinburgh. After a postdoctoral position at Northwest University in the US she returned to Edinburgh as a researcher and lecturer in Particle Physics at the University of Edinburgh’s School of Physics. Most recently she has, along with a team of other scientists and students from Edinburgh, become involved in the ATLAS experiment at the LHC, searching for the elusive Higgs boson.

What are you motivations for becoming a scientist?

Peoples ask me this occasionally and I don’t actually know. I think it was because I had a very good physics teacher at secondary school. It wasn’t a very strong decision, I kind of fell into doing a PhD - I didn’t really think too hard about it! I got offered a job at the Fermi lab collider, just outside Chicago, and it was something that I was interested in. We were able to look at high energy particles that I hadn’t looked at - Z bosons, W bosons and may be the Higgs boson and that sounded like what I would like to do if I continued in science. I’ve always enjoyed it so it wasn’t a bad decision.

What’s it like working at CERN?

CERN was set up after World War II to increase cooperation between European scientists. It has really achieved this, there is a great atmosphere of scientific collaboration and people working together towards one goal. It breeds an atmosphere of excellence.

The other point is that you can’t do such a huge experiment without involving multiple countries. There is no point doing it twice. It’s much more effective and we’ll do better science if we all do it together and it saves money.

What science are you involved in out at CERN?

We officially joined the ATLAS collaboration in September. It is a fairly big team from Edinburgh with two lecturers; three post doctoral assistants and three students, all working on various aspects of the project.

Very generally ATLAS is an experiment at the LHC (large hadron collider) that just sits where the two protons are brought in to collide and watches and records what happens. The ATLAS detector itself is huge, it is 40m high. One of the parts is maintained by a student based in CERN who makes sure that this detector is kept cold enough.

What I’m doing sitting here in my office in Edinburgh is working on software for the experiment. It takes a lot of data and coping with all that data is what some of my colleagues in Edinburgh are doing. I work on interpreting the data. One way we can do that is by making a simulation of the detector to model what goes on during a collision. If we find differences between the simulated and the real experimental data we will try to understand what went wrong with our understanding of the simulation programme, or detector, or physics. Or perhaps it is something really exciting - some physics that we have never thought about suddenly appeared.

The third thing that we are doing in Edinburgh is a very long term project. In seven to nine years some parts of the detector will be replaced since they are too old and too radiation damaged to work with. We have had meetings to show what facilities we have here to build a new piece of the detector - really exciting, actually build a part of ATLAS at Edinburgh.

So is the LHC now up and running?

They switched on the LHC at the end of November 2009 and it just worked fabulously well. We were all thinking it was about to break again and it didn’t! It had been running all the way up to Christmas at different energies. Now they are doing some analysis to determine how the machine performed and if there are any ways of making it work better. The plan now is to switch it back on in February and increase the energy and the number of protons in the collider.

What are you hoping ATLAS will see in during these higher energy collisions?

Well what will grab the headline is if we ever see this particle called the Higgs boson. We have two students looking at the very first data we got out, but we don’t expect to see the Higgs boson yet.

The Higgs boson was one of the main motivations for building the accelerator but it is involved probably only in 10% of the work going on.

Why is everyone so excited about the Higgs Boson?

We have this model that doesn’t have a very sexy name; it’s called the Standard Model but it is very beautiful because it works extremely well. It says there are 12 different particles and predicts the ways that these particles interact through three different forces. It describes these in a mathematical framework, but all the predictions made by this model have been experimentally tested and verified.

The model also predicts one thing that we haven’t seen yet - the Higgs boson. The Higgs boson explains one thing that the standard model doesn’t tell us, which is why all particles have a mass, such that the standard model without the Higgs boson doesn’t actually make any sense!

But the model doesn’t tell us the mass of the Higgs boson. So we cannot design one very simple experiment to make the Higgs boson because we don’t know how heavy it is. That is why you have to come up with something like the LHC which can look for a whole range of masses and watch to see if we have made Higgs bosons.

How will we know if we have seen a Higgs boson?

The Higgs boson we can create will decay very, very quickly; within 10-25 seconds. Fortunately the standard model tells us what it will decay into, but that depends a bit on what mass it is. So we go off and look for the particle it is going to decay into in the experiment. That tells us if we have found it.

So what if you don’t see the Higgs boson at all?

Well the standard model must be wrong. As physicists we believe that there is a nice way to describe what is going on so there must be some other models. People have thought of other models that explain the data we have without a Higgs boson. So we’d probably go back and look at those models and see what other predictions they make and test them.

Most people think that if there isn’t a Higgs boson there has to be something else. There is a fundamental theoretical reason for that. If you don’t have the Higgs boson or something else you’d start producing more W bosons than you’d put in and that can’t happen. There has to be something to regulate this production of W bosons and the Higgs is one way to explain it. So generally there would have to be something, either the Higgs boson or something totally new otherwise the whole fundamental understanding of particle physics doesn’t make sense.

And what about if you do see the Higgs Boson?

We’ll have a big party, open the Champagne, publish the papers, but we’d still have to do a lot of work to check out whether it is really the Higgs boson that the standard model says or somehow a different Higgs boson. It may take 3 years’ data to discover the Higgs boson, but it’s going to take 10 years to really understand the all the properties of whatever it was we saw.

What do you think was the effect of the big flop and all the reports that the LHC would create a world destroying black hole had on the public’s attitude to the LHC?

I was very excited that people and the media wanted to show this, because it is a project that people have been working on for the last twenty years. Furthermore since the tax payers pay for it we have to tell them what we are doing with the money and why we are doing it.

It was unfortunate that we got very excited when we turned the accelerated on and it broke, maybe the people who deal with the media should have managed people’s expectations better. These things will happen again probably with less collateral damage and we will switch the accelerator back on and forget about it.

Alex Sinclair is a PhD student in the Centre for Science at Extreme Conditions


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