Research project Solving the HIggs Fine-Tuning Problem with Top Partners
In the Standard Model, the mass of the Higgs boson is greatly destabilised by quantum corrections, and free parameters of the model need to be extremely fine-tuned in order to arrive at the measured Higgs mass.
In the SHIFT project we aim to find the underlying mechanism protecting the mass of the Higgs boson from large quantum corrections. The leading correction, which arises from the top quark, can be cancelled by introducing top-quark partners to the theory.
Therefore we study possible signatures of such top partners and search for them using data from the ATLAS experiment at CERN’s Large Hadron Collider.
The project which is funded by the Knut and Alice Wallenberg Foundation, involves theorists and experimentalists from Chalmers University of Technology, Stockholm University and Uppsala University and runs over five years (2018-2022). It covers direct searches for top partners in supersymmetry and compositeness models and indirect searches via precision measurements of processes involving top quarks.
Project description
SHIFT Research tracks
The project follows three different and complementary tracks: direct searches for the scalar top squarks in SUSY, direct searches for the vectorlike top quarks in compositeness models and indirect searches for top partners which are not kinematically accessible at the LHC collision energies.
Research tracks / Direct SUSY searches
Coordinator: Sara Strandberg
In SUSY, every SM particle has a hitherto unobserved superpartner with similar properties but with a spin that differs by half a unit. The fact that the scalar Higgs boson is related to a fermion implies that the Higgs boson mass is protected by chiral symmetry. The new particles that remove the dominant source of fine-tuning are the superpartners of the top quark, the scalar top squarks (stops).
Research tracks / Direct compositeness searches
Coordinator: Elin Bergeås Kuutmann
In compositeness, the Higgs boson is a composite pseudo-Nambu-Goldstone boson (pNGB), arising upon the spontaneous breaking of a global symmetry in a new strongly coupled sector. Thus, in compositeness, the Higgs boson mass is protected by a Goldstone shift symmetry. The new particles that remove the dominant source of fine-tuning are vector-like additional top quarks.
Research tracks / Indirect searches
Coordinator: Jörgen Sjölin
If the mass of the top partners and other particles is too high for direct detection, the only observational link remaining is the residual interactions causing the couplings between SM particles to be modified as well as new couplings to arise. The high energy interactions can thus be described at low energies in a model-independent way using effective field theory (EFT). In EFT the details of the high mass physics are integrated out of the theory and what remains is a limited set of effective operators with associated constant coefficients.
Project members
Project managers
Sara Kristina Strandberg
Professor
Members
Christophe Marcel Victor Clement
Professor
Jörgen Sjölin
Universitetslektor
David Milstead
Professor, KVA-forskare
Dongwon Kim
PhD Student
Ellen Maria Riefel
PhD student
Xuanhong Lou
Postdoc
Antonia Strübig
Postdoc
Publications
News
More about this project
Members who do not belong to SU are listed below.
Senior members
Elin Bergeås Kuutmann, Uppsala University (experiment)
Rikard Enberg, Uppsala University (theory)
Gabriele Ferretti, Chalmers University of Technology (theory)
Associate members
Rachid Benbrik, Cadi Ayyad University (theory)
Yao-Bei Liu, Heinan IST / Southampton University (theory)
Stefano Moretti, Southampton University / Uppsala University (theory)
Postdocs/Researchers
Diogo Buarque Franzosi, Chalmers University of Technology (theory)
Venugopal Ellajosyula, Uppsala University (experiment)
Luca Panizzi, Uppsala University (theory)
Associate members
Tanumoy Mandal, Delhi University / Uppsala University (theory)
PhD students
Thomas Mathisen, Uppsala University (experiment)
Associate members
Max Isacson, Uppsala University (experiment)
Associate international collaborators
Juan Antonio Aguilar-Saavedra, Universidad de Granada (theory)
Andy Buckley, University of Glasgow (theory)
Christoph Englert, University of Glasgow (theory)
James Ferrando, DESY (experiment)
Roberto Franceschini, Università degli Studi di "Roma Tre" (theory)
Fabio Maltoni, Catholic University of Louvain, CP3 (theory)
David Shih, Rutgers University (theory)
Michael Spannowsky, Durham University (theory)
Riccardo Torre, CERN (theory)