Report
Teaser, summary, work performed and final results
Periodic Reporting for period 2 - MULTISCALE (Precision Multi-Scale Predictions for the LHC: Higgs, Jets and Supersymmetry)
Teaser
The Large Hadron Collider (LHC) is leading the search for new physics at the shortest distance scales. The LHC has discovered the Higgs boson, and precise measurements of its properties or other scattering processes may lead to the discovery of physics beyond the Standard...
Summary
The Large Hadron Collider (LHC) is leading the search for new physics at the shortest distance scales. The LHC has discovered the Higgs boson, and precise measurements of its properties or other scattering processes may lead to the discovery of physics beyond the Standard Model. To identify small deviations in the data requires precise theory predictions, which is the aim of this project. We focus on the effect of the strong force, that is the dominant source of uncertainty. In particular, we address the multi-scale nature of collisions at the LHC, allowing us to obtain predictions that are also realistic, i.e. provide a sufficiently detailed description of the final state of the scattering processes. (Technically, hierarchies between scales lead to large logarithms in predictions for the rate of a process, causing standard perturbation theory to deteriorate or break down, which we address using resummation.)
The overall objectives are: the development of new effective field theories to account for these multiple scales in scattering processes at the LHC, and their application in the context of precision Higgs measurements, jet substructure techniques and supersymmetry searches. Jets are sprays of collimated hadrons, which are produced copiously at the LHC, and jet substructure exploits their internal structure to e.g. identify the particle initiating the jet. This is particularly interesting for jets that arise as the decay of a Higgs boson or other heavy particle.
This is fundamental research that will help shed light on the laws of nature at the shortest distance scales. While direct applications to society are not foreseen, it is worth pointing out that many discoveries in physics, that are now widely applied, started out this way.
Work performed
We have developed the effective field theory framework to account for multiple scales in scattering processes, addressing in particular hierarchies between scales induced by: multiple observables, hierarchies between jet energies or angles, and/or the size of the jet. We have obtained results for a range of applications in the context of jet substructure and supersymmetry searches. During the course of this project, we also identified and investigated new opportunities for applying these ideas: to measure the distribution of the intrinsic transverse momentum of a quark or gluon in the proton using jets, to calculate the effect of the electroweak force in scattering processes, and in the calculation of the rate for top quark pair production.
Final results
We are in the process of finalizing our predictions for the Higgs plus one jet process at the LHC, and will subsequently study Higgs plus two jets. There are also several ongoing projects in the area of jet substructure. For example, calculating the effect of grooming on jets (which is experimentally used to remove contamination, but introduces yet another scale in calculations), and exploring the possibility of obtaining reliable predictions for the simultaneous measurement of a several observables (which is used as input for modern machine learning techniques).