ELEMENTARY PARTICLE PHYSICS

The Standard Model (SM) refers to the theory that classifies all known subatomic particles and describes the electromagnetic, weak and strong interactions among them. Experimental evidence collected so far are all in excellent agreement with the theory. In 2012, the last missing particle predicted by the SM, namely the Higgs boson, was discovered in the Large Hadron Collider (LHC). Despite the remarkable success, it is generally believed that there are phenomena beyond the SM. The justifications include, among other things, the observational evidence of dark matter and the theoretically unsatisfactory property leading to the so-called “hierachy problem” regarding the Higgs boson mass.

In an attempt to extend the SM, lots of Beyond Standard Model (BSM) theories have been proposed. One class of such theories postulates that the observed Higgs boson, rather than a fundamental particle as described by SM, is indeed a composite particle composed of new subatomic particles bounded by new interactions, in analogy with the known composite particles (hadrons) formed by subatomic particles (quarks) bounded with strong interaction. Such new particles and interactions not only lift the hierarchy problem, but also lead to new composite particles that may naturally become dark matter.

The search of appropriate candidates of such theories is very challenging. One needs to focus on several models among infinitely many models, chosen by theoretical expectations, and then compute the experimental predictions by these models. Such predictions are highly involved, and have to be numerically simulated. Space and time are replaced by a four-dimensional discrete lattice. The required large numbers and sizes of lattices imply that the simulations are only possible on powerful high performance computing systems (HPC) such as the GCS supercomputer JUQUEEN at the Jülich Supercomputing Centre (JSC).

In this project, the Lattice Higgs Collaboration (LatHC), which consists of scientists from University of Wuppertal, Eotvos University, University of the Pacific and UCSD, investigates the properties of the Sextet model, which is an analogy of the strong force with two quarks, while the quark equivalents respond to strong forces differently. The study includes the spectroscopy of its hadrons and how the interaction strength varies with decreasing probing energy, which are crucial in the feasibility of the model being a BSM candidate.

In the study, a composite Higgs boson and several new composite hadrons with masses reachable by LHC are predicted by the model. The interaction strength is found to vary slowly with decreasing probing energy, which is a favourable result. These findings have recently made the Sextet model one of the highly interesting BSM models and provide useful insights in the related search.

Team: Lattice Higgs Collaboration (LatHC)

Zoltan Fodor (Eotvos University & IAS, Jülich Supercomputing Centre & Bergische Universität Wuppertal)
Kieran Holland (University of the Pacific, Stockton & University of Bern, Albert Einstein Center for Fundamental Physics/AEC)
Julius Kuti (University of California, San Diego) 
Santanu Mondal, Daniel Nogradi (Eotvos University & Eötvös Loránd University, Budapest, Institute of Theoratical Physics) 
Chik Him Wong (PI, Bergische Universität Wuppertal)

Scientific Contact:

Dr. Chik Him Wong
Institut für Theoretische Teilchenphysik
Fakultät für Mathematik und Naturwissenschaften
Bergische Universität Wuppertal, D-42097 Wuppertal (Germany)
e-mail: cwong [at] uni-wuppertal.de