Karsten Buesser

What is the ILC?

I am spending all of my working (and a considerable part of my private) time to the ILC. So I guess it is worth to have a closer look at that:

The International Linear Collider (ILC) is the next big project of the worldwide community of particle physicists. It is expected to complement the picture which we hopefully get from the Large Hadron Collider (LHC) which is under construction right now at CERN. We know pretty much about nature on its smallest scales. We know that matter consists of quarks and leptons, we know about the four fundamental forces in nature, but there are a lot of open questions still waiting to be answered. Questions like, where are the masses of the elementary particles coming from, or the fact that our Standard Model of the world just describes 4% of our universe. That is the part of the well known matter which forms stars and planets.

We know that 23% of our universe consists of dark matter (our colleagues from astrophysics told us). This is a matter form which underlies the force gravity but it is not visible in telescopes. The best guess that we have on it, is that yet unobserved elementary particles could form that dark matter. Those particles could have been produced in the Big Bang and since then populate our universe without communicating with our known world. There exists a very promising theory, called Supersymmetry (SUSY) which forms a natural extension of our current theory of the world. SUSY predicts a number of new particles which could be the origin of dark matter.

To get a hand on these guys is difficult. The best way to do that is probably to try to simulate the Big Bang in the lab. Particle physicists do that all the time at their particle accelerators in the big labs around the world like DESY. We accelerate elementary particles like electrons to high energies and let them collide. Though the total energy in these collisions is quite small, we produce a very high energy density. This density is about as high as the energy density of the universe a few billionth of a second after the Big Bang. And if we are lucky, the energy density is large enough to produce those SUSY particles which we hold responsible for the dark matter.

The LHC at CERN will be the next machine on the energy frontier. If these particles exist, there is a very good chance that we will find them in the collisions produced there. Really understanding the properties of these particles is hard, though. The key to it are precision measurements. And for those we need precision machines. LHC is an accelerator in which hadrons collide. These are heavy particles which consist of quarks. The reactions which we expect at the LHC are therefore not easy to interpret. We know already now that we need a precision tool to complement the measurements which will come out of the LHC. And this tool is the ILC.

At the ILC we plan to accelerate elementary particles, electrons and positrons, in linear accelerators with a total length of 30-40 km (sorry my North-.American colleagues, I am living in the metric system). The plans for this machine are developing, we hope to have the Technical Design Report ready by the year of 2007. This machine we are planning is probably the most complex machine of the world, or as one of my British colleagues says: ‘This is going to be the mother of all accelerators’.

So why do I devote most of my life to it? This is a question easy to answer. The physics benefits which we are expecting from that machine are unprecedented. We are planning the tool which will produce the science for the textbooks of the coming generations. That is worth some efforts, don’t you agree? And maybe it will help some day to shed some light on the 73% of the universe, the so-called dark energy, still missing in the sum. We don’t know much about it, we just know that this dark energy reacts like an unknown force which accelerates the expansion of the universe.

Kick-Start

So finally I am at my own desk for longer than a couple of hours which gives me a chance to really start blogging.

The new working year really kick-started me into high gears immediately. I spent already the third working day on the plane, going to SLAC near San Francisco for a workshop on the ‘Machine-Detector Interface (MDI)’ of the International Linear Collider (ILC). The definition of what exactly the ‘Machine-Detector Interface’ is is really not easy and is actually still under discussion in the respective working group. Basically it deals with everything where the design of the accelerator has a potential impact on the design of the big detectors planned to record the physics reactions at the collision points of the ILC.

Well, travelling so close to the holiday season usually is a hassle: Long queues everywhere, full flights, delays, etc. I really prepared for the worst but things evolved quite nicely when British Airways upgraded me to their very nice business class on the outbound flight. Why British Airways? Well there are no direct transatlantic flights leaving from Hamburg. So whenever we have to travel outside Europe we have to go through one of the big hubs: Frankfurt, Paris, Amsterdam, London, etc. And the DESY travel policy is to choose the cheapest flights available, so I know all of these airports quite well. Usually I don’t like Heathrow too much, because it is located on an island. A few years ago this really was a problem when I was dumped in Heathrow in the biggest storm hitting the British islands since a long time. It is really hard to escape from an island when neither planes nor ferries nor trains are running….

Well this time British Airways was the right choice, everything went nice and smoothly.

The stay at SLAC was a little bit disappointing though. The workshop was interesting, the organisation was excellent, but the weather…. I mean I knew they had like monsoon season in January, but it really rained cats and dogs for the biggest part of the four days I stayed there.

Coming back a week ago I just spent two nights at home before I went to the next workshop at the Ecole Polytechnique in Palaiseau near Paris. This time it was a meeting of the physics community interested in designing a detector for the ILC based on gaseous tracking with a big time projection chamber as the heart piece. Being an expert for MDI is big fun, but it also doubles the travel. You have to be at the conferences of both parties, the machine and the detector people.

Paris is always nice. I stayed in a nice old hotel near the Pantheon. This is in the 5eme arrondisement of Paris, which is the part where most of the universities (including the famous Sorbonne) are. So there are many nice restaurants, bars and shops in this area. Not that I had much time to spend there as we had to take the 08:00 am train every morning going the 40 min ride to Palaiseau. And to get from the train station to the Ecole Polytechnique you have to climb a hill on a footpath with a very steep slope. You really curse every glas of red wine you had in the evening then….

Well now I am back at home trying to get a grip on my overflowing mailbox and task list. Of course the backside of travelling is (at least here at DESY) that you are the natural candidate to give a report about the workshops you have been at at the next regular meetings here. So now I have to prepare a summary of the MDI and the detector workshop for our weekly ILC project meeting on Friday as well as for our internal group meeting on Monday.