The LHC provides the highest beam energies world-wide for protons and for Pb-nuclei. Experiments are thus able to provide systems with higher energy density and temperature as ever before. While important hints of the quark-gluon plasma state have been found in earlier, lower-energy experiments, the LHC, and in particular the ALICE experiment is the optimum place to study the physics of the quark-gluon plasma. The signatures of the new state of matter should be yet clearer and more striking here than at lower energies. Our group has played a leading role in the design and construction of one of the major detectors of ALICE, the Silicon Strip Detector (SSD), which is part of the Inner Tracking System (ITS). The SSD is a cylindrical detector consisting of approx. 2.5 million individual detector channels. One of the most demanding features of this detector has been its extremely lightweight design. It has been assembled at the university, has been installed in 2007 in the ALICE experiments and has been successfully taking part in measurements since the first collisions in the LHC. The group is also very active in the analysis of the measured data. We are continuously developing computer algorithms for these tasks. Together with our colleagues from many institutes all over the world we have been able to demonstrate a number of interesting properties of the hot and dense matter produced in the collisions:
- The matter has extremely high density and temperature.
- After its creation, the system expands with a velocity close to the speed of light.
- It is opaque to even the most penetrating high-energy quarks and gluons.
- The matter behaves almost as a perfect liquid, i.e. it has a viscosity smaller than any other liquid known.