Our current understanding of elementary particle dynamics relies on Quantum Field Theory, an approach that combines quantum mechanics with the theory of special relativity. Quantum Field Theories are very complicated, and obtaining theoretical predictions for physical processes from the definition of the theory itself is an open challenge. Thus, in practice, we use a tool, called perturbation theory, to compute physical observables in an approximate way. This way is systematically improvable by including more and more orders in the perturbative expansion; however, computations at high orders become increasingly complicated, and thus unaccessible beyond some point.
The work performed in this project faces with this problem from two complementary directions.
- On the one hand, it overcomes the computational difficulties by using techniques to resum to all orders the perturbative expansion in certain kinematic limits. This approach is still approximate, but it can capture the bulk of higher order corrections, thus improving significantly the quality of the prediction. In this project a particular kinematic regime has been considered, the so-called high-energy limit, and state-of-the-art all-order theoretical predictions have been computed. In this regime these contributions have a sizeable effect, and allowed us to obtain a significantly better knowledge of the structure of the proton.
- On the other hand, this project proposes a novel way to quantify the uncertainty induced by our approximate knowledge, by constructing a statistical model to estimate unknown higher orders from the known ones.
Among the results of this project a very interesting one is the impact of the resummation of the aforementioned contributions in the prediction of the production rate of a Higgs boson at a proton-proton collider. At the energy of LHC, the impact of this resummation is mild, but for higher collider energies, such as those planned for a Future Circular Collider at CERN, the effect reaches up to 10%. This result is impressive, as the (indirect) discovery power of such machines requires accuracies at or below the percent level. This important achievement shows the need for considering such high order contributions and opens up a new phase of precision at colliders, with many potential future developments.
The outcome of the project includes 7 published papers, 3 conference proceedings, 5 working group reports. The dissemination has been performed also through the participation with oral contribution to 8 international conferences and workshops.
