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High Precision Simulation of particle collisions at the LHC

Final Report Summary - MCATNNLO (High Precision Simulation of particle collisions at the LHC)

The first few years of data-taking at the Large Hadron Collider (LHC) at CERN, Geneva, have been amazingly successful, with new results on a multitude of aspects of particle physics arriving at an unpredecented rate. Many of these results have, or will have, a huge impact on our understanding of fundamental particles and their interactions at the highest energy scales. They will inevitably shape mankind’s view of the universe and the rules according to which its most basic building blocks interact.

Clearly, the most prominent and arguably the most important outcome so far is the discovery of a new boson, with properties that appears to be fully consistent with a Standard Model Higgs boson. This discovery is a first step towards a full understanding of the mechanism of electroweak symmetry breaking and the origin of particle masses. Now the experiments at the LHC are analysing this new particle in ever greater detail in order to ultimately prove or disprove the Standard Model mechanism of broken gauge symmetries. Precise measurements of the properties of the new boson are now mandatory and must be reflected in a similar quest for higher precision from the theory side.

At the same time, the LHC experiments continue with searches for further new particles, interactions, and building principles. The first round of such searches has not produced “smoking gun” evidence for any new phenomena. These searches are continuing and are now probing scenarios that produce much more subtle signatures. The quest for increasing precision from the experimental side must be matched by a theoretical description of hadronic collisions that is similarly precise.

This ERC-funded project aimed to establish a new standard of theoretical precision for the description of collider observables. This is being achieved by developing a numerical framework for the calculation of the next-to-next-to-leading order (NNLO) perturbative corrections to exclusive observables and by the systematic inclusion of such calculations in relevant simulation tools. So far, the project has led to some of the most precise predictions of benchmark processes ranging from the inclusive Higgs cross section, to vector boson pair production, jet production and Higgs and vector boson production at large transverse momentum. We find that these more precise calculations generally reduce the tension between theory and experiment and have so far lead to an improved agreement with the experimental data, thereby placing tighter constraints on possible new physics beyond the Standard Model.
We also developed a number of new techniques and results for going beyond the planned scope of the project to make even more precise predictions.