Top-Higgs sector and simplified models

• Applicant: Professor Dr. Tilman Plehn
• Subject Area: Nuclear and Elementary Particle Physics, Quantum Mechanics, Relativity, Fields
• Term: from 2015 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 257416295

The discovery of a Higgs particle raises fundamental theoretical questions. After Run 1we have no experimental indication that the observed narrow Higgs resonance is not anelementary particle. However, studies of the ultraviolet structure of the Standard Modelsuggest that for such an elementary state we can extract relevant information from the LHC Higgs data about the scalar potential at high energy scales, such as the stability of the Higgs potential, the so-called triviality bound, and the general behavior of scalar particle masses in the ultraviolet. On the other hand, in QCD and in many other areas of physics, symmetry breaking occurs through strong interactions and a shift in the relevant physical degrees of freedom. In that case the low-energy renormalizable Higgs Lagrangian would have to be extended by higher-dimensional operators, originating from new strong interactions at energies not too far above the weak scale.Furthermore, the top quark remains the second mysterious particle in the Standard Model, distinguished from the other fermions by its large mass. If one assumes the flavor structure of elementary particles, in particular the pattern of Yukawa couplings, has a common origin at a high scale, the large top quark mass could indicate that the top Yukawa coupling experiences stronger renormalization group evolution than the other fermions. This is a strong indication of possible new particles beyond the Standard Model, making the top quark a prime target for new physics searches. Most importantly, the large top-Higgs coupling suggests that we should maybe look at the Higgs boson and the top quark as one strongly coupled physics sector, no matter what the underlying physics beyond the Standard Model might be.In this project we propose a comprehensive study of the top-Higgs sector as a tool to look for physics beyond the Standard Model. This includes the measured Higgs properties, new LHC signatures in and beyond the Standard Model, subjet methods as a new analysis approach, and an investigation of the top-Higgs sector evolved to high energy scales.

• DFG Programme: Research Units
• Subproject of: FOR 2239: New Physics at the Large Hadron Collider
• Co-Investigators: Professor Herbert Dreiner, Ph.D.; Professor Dr. Joachim Kopp