Measurement data collected by the ATLAS experiment at CERN, on the border between Switzerland and France. Photo credit: CERN.

“We know what now the Higgs particle weighs. The problem is that if you use the current Standard Model for particle physics to calculate the mass, it ends up much, much bigger than the measurements. You can adjust the different contributions to mass so that it reflects reality, but it’s messy. And, historically, adjustments like this are often a sign that something is off”, says Sara Strandberg, Department of Physics, Stockholm University, and project leader.

The project is searching for new particles that could explain Higgs boson’s tiny mass. Because the top quark, another elementary particle, is the biggest contributor to Higgs boson’s mass according to the calculations of the Standard Model, the researchers will search for another particle with similar qualities. This hitherto unknown particle is a sort of relative to the top quark.

Sara Stran

Sara Strandberg. Photo: Vilhelm Stokstad. 

“Theoretical and experimental physicists worked separately before, but now we Stockholmers collaborate with physicists in Uppsala and at Chalmers to look for the top quark’s unknown cousin. We have international partners, too”, says Sara Strandberg.

The project’s measurement data comes from the ATLAS experiment, which records proton collisions from the LHC particle accelerator at CERN. The Swedish researchers, alongside researchers from around the world, are collecting data and analysing them in new ways.

Project: “Solving the Higgs Fine-Tuning Problem with Top Partners” is financed for 5 years.

About the grant:

Every year the Knut and Alice Wallenberg Foundation awards grants to research projects which are judged to be of the highest international standard with the potential to lead to future scientific breakthroughs. In 2017 the foundation awarded 560 million SEK (69 million USD) to 18 research projects. Stockholm University received two of these grants for a total of just over 55 million SEK (6.8 million USD).