Research project Supersymmetric Top Quark Partners at the LHC

A supersymmetric extension of the standard model can solve the fine-tuning problem of the Higgs mass and explain dark matter. In this project we search for the supersymmetric partner of the top quark with data from the ATLAS experiment at CERN.
Supersymmetriska partnerpartiklar till toppkvarken vid LHC

Supersymmetriska partnerpartiklar till toppkvarken vid LHC

The main objective of the project is to search for new particles which presence can solve the Higgs fine-tuning problem. In the Standard Model of particle physics, the top quark gives rise to a large quantum correction to the Higgs boson mass which has to be counter-balanced by a fine-tuned free parameter in order to arrive at the measured Higgs boson mass. The correction from the top quark can be controlled by introducing a supersymmetric top-quark partner (stop) with a mass below approximately 1.5 TeV, i.e. within reach by the Large Hadron Collider (LHC) at CERN. As a supersymmetric extension of the current theory can also provide a dark matter candidate and allows for a unification of the electroweak and the strong forces of nature, the discovery of a stop would have implications far beyond solving the Higgs fine-tuning problem.

In this project, we conduct searches for the stop with data from the ATLAS experiment at CERN. We cover a broad range of scenarios which are still viable given the results of already existing searches. At the end of the project, the result will either be a discovery or a set of limits on the masses of supersymmetric particles. The project also involves the development of new search strategies and techniques, which are expected to be of lasting benefit and use to the field.

This research project has no members.

Department of Physics

Fysikum physicists among winners of prestigious Breakthrough Prize in Fundamental Physics

Scientists from Stockholm University are among the worldwide researchers honored with the 2025 Breakthrough Prize in Fundamental Physics, awarded to the ATLAS Collaboration at CERN's Large Hadron Collider (LHC) alongside its sister experiments ALICE, CMS and LHCb. The prize was founded in 2012 by Yuri Milner to recognize those individuals who have made profound contributions to human knowledge.

Department of Physics

Sara Strandberg on Wallenberg Scholar and the Higgs particle

The Wallenberg Scholars program supports and stimulates some of the most successful senior researchers at Swedish universities. The grant is for five years with the possibility of a five-year extension. There are currently 88 active Wallenberg Scholars and Emil Bergholtz was recently appointed. Sara Strandberg received a five-year extension. On April 12, Sara participated in the Swedish Radio program Vetenskapsradion on the topic of the Higgs particle.

Department of Physics

A scientific train journey to CERN with Sara Strandberg

On 15 April, the train departs from Stockholm to Geneva and cicerones are particle physicist Professor Sara Strandberg from Fysikum and science journalist Anna Davour from Forskning & Framsteg. Participants will learn more about the smallest components of our matter with quarks, leptons and other elementary particles. CERN is the world's largest particle physics laboratory and home to the Large Hadron Collider - the world's largest particle accelerator. The particle physics group at SU conducts research on the role of the Higgs particle in various extensions of the current Standard Model. We are also a driving force in projects concerning supersymmetric extensions of the Standard Model that can, among other things, solve the Higgs fine-tuning problem and explain dark matter. "In a large project funded by the Knut and Alice Wallenberg Foundation, we are searching for the supersymmetric partner of the top quark using data from the ATLAS experiment at CERN. We have pushed our limits on the masses of supersymmetric particles, and developed new search strategies and techniques that are expected to be of lasting benefit to the field," Strandberg explains. The project ended at the end of the year, but the scientific collaborations continue. Thanks to a new grant from the Swedish Research Council to the Swedish LHC consortium, Sweden's participation in the ALICE and ATLAS experiments at the LHC is funded for another 6 years. This means that it will be possible to continue experimental research at the LHC. The consortium consists of one representative per university from Stockholm University, KTH, Lund University and Uppsala University. In total, about 150 people in Sweden are involved in research at CERN, of which about 100 are involved in the LHC experiments. In addition to the city tour and the visit to CERN, participants will also visit a vineyard where local wines are produced. "There may also be a science quiz during the train journey," says Sara Strandberg.   More information Train trip to CERN (in Swedish) CERN (Conseil Européen pour la Recherche Nucléaire) LHC (Large Hadron Collider) - The worlds largest particle accelerator ALICE experiment ATLAS experiment Higgs Boson - Higgs boson Professor Sara Strandberg, Fysikum World's largest particle accelerator restarts An Open Lecture with Sara Strandberg talking about the ATLAS experiment

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