Novel computational techniques in particle physics

Since the discovery of the Higgs boson at the Large Hadron Collider (LHC) at CERN, the Standard Model (SM) for particle physics has been a complete, self-contained theory. Indeed, this theory has been thoroughly tested and repeatedly confirmed in collision experiments over recent decades: All of the predictions made in the SM have been borne out, and no conclusive evidence has yet been found of deviations from the theory.

Is this a satisfactory result from the point of view of particle physics? Unfortunately not, because the universe confronts us with problems that cannot be entirely explained by the particles and interactions described in the SM. The existence of dark matter is one example: We can observe that dark matter exists, but we don’t know what it is made of. Likewise, the neutrino – an elementary particle in the SM – is shrouded in riddles, such as how much it weighs and why it has a mass in the first place.

In addition, particle physics also wants to get to grips with a number of theoretical questions, such as what mechanism stabilizes the value of the mass of the Higgs boson or why the strong interaction – unlike the weak interaction – does not violate the CP symmetry. Furthermore, scientists are searching for ways to accommodate gravitation within the quantum physical description of the universe.

These and other unsolved fundamental questions point to a new physics beyond the SM. In accelerator experiments such as the LHC or Belle II, scientists are attempting to provide evidence of this new world of physics. In the process, hitherto unknown particles or forces may be encountered and detected directly – or indirectly based on the frequencies of certain events: If, statistically speaking, fewer or more of the expected particles are produced, that strongly suggests that physics is taking place outside the SM.

However, it would not be possible to identify outliers from the SM without precise theoretical calculations, for these are able to make well-founded predictions about the expected results. In the Department for “Innovative calculation methods in particle physics” at the Max Planck Institute for Physics, scientists devote their time to mathematical calculations relating to collision events at the LHC and possible future colliders. This allows physicists to make statements about the energy region in which hypothetical particles ought to exist.

The Department’s specific subject areas include:

• Physics of jets in collider physics
• Higgs physics, diboson production, vector boson fusion processes
• Distribution functions of photons and leptons in protons
• Calculations that include logarithmically enhanced terms to all orders in perturbation theory predictions
• Next-to-leading order (NLO) and next-to-next-to-leading order (NNLO) quantum chromodynamic (QCD) perturbative calculations