International Physics Masterclasses

Discover the Unknown

Our current understanding of how matter and forces work together to create the Universe we know is elegantly put into a theoretical framework known as the Standard Model (SM). New physics phenomena are expected to show up at very high energies. The LHC is called a "discovery-machine", and is built to explore a new energy regime – the TeV scale – and possibly reveal some of the still hidden sides of Nature.

How can we build gigantic experiments, like the ATLAS detector just based on mysteries? The answer lies in the fact that inventive physicists have thought of ways to explain one or several of Nature's puzzles. The new ideas are then incorporated into a more powerful theory that is able to predict the outcome of new experiments. New phenomena often result in additional heavy matter or force particles. They may also involve new extra space dimensions. Computer simulation of collisions that allow such new phenomena is then performed.

With simulated data one can do analysis exactly in the same way as with real data. For instance look at collision visualizations in HYPATIA, and select tracks to form invariant masses. If the simulation data contains a heavy neutral particle not yet discovered, this can for example show up in the invariant mass plot, although at a mass well above that of the Z boson. This means that the method you have just mastered, identification of Z decays and the reconstruction of invariant mass, are tools to discover the Unknown!