This week I went up north, not the Philip Pullman kind, but at least to Hamburg, which, viewed from Munich, seems to be halfway to the north pole.
Allegedly, the weather is always bad here, I guess this is the reason why every local speaker at the workshop I am attending at DESY feels obliged to mention, with a suitable level of reverence, the fact that the sun is actually shining, with not a single cloud in sight.
Of course I am not here to witness a rare meteorological event, but purely for scientific reasons. I am at the detector workshop of the Helmholtz Alliance “Physics at the Terascale”, where detector development projects for high energy physics at German institutions are discussed. The Terascale Alliance is a research network, where all German universities and labs involved in high energy particle physics participate. I am actually one of the two representatives for my institute, the MPI for Physics. The goal of this Alliance is to improve the collaboration between German institutes and to establish improved structures in the particle physics landscape.
So, what does “Terascale” stand for, apart from being a catchy name? It actually refers to the energy regime that is now reached with the newest generation of accelerators: Collision energies of tera electron volts (TeV), or 1000000000000 electron volts. The electron volt (eV) is the energy unit we particle physicists use constantly, and it is the energy an electron gets when traveling through an electric potential difference of one volt. In everyday units, this is a tiny amount of energy. However, a TeV starts to become something almost macroscopic, approximately the kinetic energy of a mosquito, something you actually feel when it hits your forehead. Still does not seem like a lot, but all this in a single particle is truly spectacular.
So, physics at the Terascale usually means the experiments at the Large Hadron Collider and at the planned International Linear Collider. Particle physicists, including myself, have high hopes that something new, maybe even unexpected, turns up at this new energy scale, which will show us how physics looks like beyond our current understanding. To make these experiments possible, new detector technologies need to be developed. These detectors are the devices that record what happens in particle collisions, which gives us the necessary information to make sense of it all and to understand the underlying principles of nature. Such new technologies were discussed at the workshop here in Hamburg, both for a future phase of the LHC experiments (for the first phase of LHC running, the detectors are all in place), and for the ILC, which is my primary interest in this. I gave a presentation about calorimetry at the ILC, the field I am working on. These detectors, called calorimeters, measure the total energy of particles by completely absorbing them. A small fraction of their energy is deposited in sensitive material in the detector, which in turn is converted into electrical signals which are then read out. How all this works in detail is coming soon, for now I’m ready for the weekend, with just an one hour flight back to Munich left to do. The flight is delayed, but not by much at present, so keep your fingers crossed.