Scientists at the Institutes of Physics at the University of Zurich and Johannes Gutenberg University Mainz (JGU) have succeeded in calculating a particularly accurate model prediction for an important scattering process at the Large Hadron Collider (LHC): the pair production of Z bosons. New analytical methods based on modern mathematical and computer algebraic techniques were developed for this purpose. “Our methods allow a large number of precise and detailed predictions for the currently frequently discussed pair production of Z and W bosons,” explains Dr. Andreas von Manteuffel from the Institute of Physics at JGU. In particular, these precise predictions are necessary in order to discover possible effects of so-called new physics beyond the standard model in these processes. The Standard Model of Particle Physics can describe almost all physical observations, but it has gaps, which is why new physics is being sought worldwide.

At the LHC, a large accelerator ring at the European research center CERN near Geneva, highly accelerated protons are brought to collision and the resulting particles are precisely measured. The aim of these scattering experiments is to understand the fundamental components of matter and their interactions. The exchange particles of the weak nuclear force, the Z and W bosons, play an important role here, e.g. pairs of these particles occur in decays of the recently discovered Higgs boson.

Precision calculations for such processes in the context of perturbation theory can be carried out with the aid of so-called loop diagrams, whereby the accuracy, but also the difficulty of the calculation, increases with the number of loops per diagram. Analytical methods and computer programs that make heavy use of symbolic algebra systems have been developed to evaluate the two-loop contributions. The special Mathematics functions that arise, so-called multiple polylogarithms, were treated with new algorithms based on the coproduct.

The scientists expect that the combination of these different Technics Departments will provide a basis for predicting other scattering processes with much greater precision than was previously possible.

The work was carried out as part of an international collaboration within the Mainz Cluster of Excellence “Precision Physics, Fundamental Interactions and Structure of Matter” (PRISMA) and the work groups of Prof. Dr. Thomas Gehrmann, Prof. Dr. Stefano Pozzorini and Dr. Massimiliano Grazzini from Zurich.