Physics at the Large Hadron Collider

Particle accelerators have allowed us to systematically probe nature at ever smaller distance scales. They have provided unique information from the structure of atoms one hundred years ago to the discovery of new elementary particles, the gauge structure of their interactions, and discovery of the Higgs boson in 2012. The Standard Model (SM) currently describes all known particles and their interactions, but despite its enormous success, many fundamental questions remain unanswered. What is the nature of Dark Matter? What is the origin of the three generations of fermions and of their seemingly random patterns of masses and couplings? Is there a link between fermions and bosons? Why do we observe such an enormous discrepancy between the amount of matter and antimatter present in the Universe? Ideas that solve these problems all predict new phenomena or new particles to appear at smaller distance scales (that is, at very high energies).

The most powerful accelerator today is the Large Hadron Collider (LHC), located at the CERN laboratory in Geneva, Switzerland. The LHC accelerates and collides protons and by studying in detail the particles produced in these collisions we can fingerprint nature at these distance scales where we hope to find answers to the pressing open questions listed above. Members of the Amsterdam physics community provide a crucial contribution to the LHC efforts by participating in the ATLAS and LHCb experiments as well as with theoretical simulations of collider processes. The ATLAS experiment studies particles at the highest energies. In combination with high collision rates, it allows to study in detail the Higgs boson, gauge bosons, and heavy particles like the top quark. We also look for new particles and phenomena predicted by theoretical extensions of the Standard Model. At the LHCb experiment, we focus on differences between matter and anti-matter. Precision measurements allow to study differences between lepton families and probe details of the quark mixing matrix. In both experiments we are involved in detector R&D, data-acquisition and computing. Theoretical particle physicists in Amsterdam carry out precise predictions for relevant LHC processes, both with and beyond the SM, develop data interpretation frameworks based on effective field theories, and exploit machine learning tools to optimise the sensitivity to new phenomena.

Plot caption: left: visualisation of a collision recorded by the Atlas detector of a Higgs boson (decaying into two photons) produced in association with two top quarks, middle: on of the many di-pole magnets in the LHC tunnel and right: the Lagrangian of the Standard Model.

People to contact on this: Atlas experiment: Wouter Verkerke LHCb experiment: Marcel Merk Theory: Juan Rojo