The story of ALICE
The discussions about the future of heavy-ion physics at CERN started in 1986, even before the building of the Large Electron-Positron Collider (LEP) had been completed. Four years later the idea of creating a dedicated heavy-ion detector for the Large Hadron Collider was born and on 13 December 1990 the Heavy Ion Proto Collaboration (HIPC) held its first meeting. Later on, during the historic Evian meeting “Towards the LHC experimental programme” in 1992, the expression of interest to create ALICE was submitted, followed by the letter of intent in 1994 and by the technical proposal in 1995.
One of the people, responsible for the creation of ALICE, is Jurgen Schukraft. Spokesperson of the collaboration for the first 20 years of its existence, he is also the person who organised the initial meeting of HIPC. In the following interview we will try to show you the evolution of ALICE through his eyes.
Has ALICE changed much since the beginning?
Jurgen: In the beginning, the plan for the experiment was different from what it eventually turned out to be. We had a big TPC, we had a silicon vertex detector, we had time of flight, but the magnet was completely different. Ever since we sent the letter of intent, we had many different ideas. All the details were missing and we made a lot of additions afterwards, but the essential part of the detector was already decided by 1992.
In terms of the collaboration, it was very different at the time, because most of the people at CERN were doing experiments at low energies – the LEP programme at CERN. The Large Hadron Collider was still far in the future. It was after the approval of the technical proposal in 1994 when we started some serious research and development. In 1998, when the SPS experiment stopped, more people joined our collaboration.
Which are the most interesting discoveries, made in ALICE?
Jurgen: We have made many discoveries so far, but one thing which we did not expect is that each of these little “big bangs” has its own character. These explosions are so strong that every one of them is different and individual. This couldn't be observed in the other types of collisions, where we only look at the average properties of the particles.
The other very interesting thing for me is the discovery that there is a much deeper connection between all the QCD processes – everything which involves strong interaction – they are much deeply connected than we originally thought.
I think it would be very good if in the next 10 or 15 years we manage to embed what we have learned from the heavy-ion physics into the bigger context of the standard model.
Are you happy with how the experiment developed?
Jurgen: I think overall it worked out as well as we could have hoped. The physics at the LHC turned out to be extremely interesting. Even more interesting than we initially thought. Also, the experiment worked very well. There are always things that could be done better, but we constantly learn. That is why ALICE is going to be upgraded during the next long shutdown.
In addition, more people came to the collaboration than we thought would join. There are currently about 1500 members. In these terms we developed even better than I hoped. I am pleased and also proud of our community and of the fact that we managed to create such a huge experiment.
We were a bit naive in the beginning, thinking that 10-12 years were going to be enough to do what eventually took us 20 years. A bit naive, but also very enthusiastic. What I am happy about is that we didn't have big disappointments along the way. On the contrary – we had a very satisfactory development. This project was more complicated, more expensive and much bigger than what we had done before. It was a big mountain to climb and I am proud that we managed to get to the top.