Joscha Ahäuser selected as new co-convener of the CMS Top Quark Physics Analysis Group

Dr. Joscha Ahäuser, a postdoctoral researcher in the group of ETP professor Jan Kieseler, has been selected as the new co-convener of the CMS Top Quark Physics Analysis Group (TOP PAG). The two-year term will begin in September 2026. Within the CMS Collaboration, the TOP PAG coordinates and reviews measurements and searches related to the physics of the top quark, the heaviest known elementary particle.

Top quark studies at the LHC play a central role in precision tests of the standard model of particle physics. The TOP PAG oversees measurements of production rates and properties of top quarks, including rare processes and precision determinations of fundamental parameters, as well as searches for new phenomena. These measurements are also essential inputs for improving our knowledge of the proton structure, encoded in parton distribution functions, and for probing physics beyond the standard model. Because of its large mass and its strong coupling to the Higgs field, the top quark is particularly sensitive to the mechanism of electroweak symmetry breaking. Recent highlights include studies of the top quark–antiquark production threshold region, which has been interpreted as evidence for a possible short-lived “toponium” quasi-bound state, as well as a wide program of interpretations in frameworks such as the standard model effective field theory and searches for flavor-changing neutral currents.

The coming years will be especially important for the field, as the LHC Run-3 dataset, more than 300 fb⁻¹ of proton–proton collisions, is now fully available. This unprecedented dataset will enable major improvements in precision and discovery sensitivity across top quark measurements. Dr. Ahäuser joined the ETP CMS team in September 2026 and works on studies of four-top and Higgs-associated top quark production in multilepton final states, as well as on improvements in electron reconstruction and identification in CMS. He is also involved in preparations for the FCC-ee. Speaking about the appointment, Dr. Ahäuser says:

“This is an extremely exciting time for top quark physics, with the full Run-3 dataset opening a new level of precision and discovery potential. I am very much looking forward to helping to shape the top quark physics program in the coming years.”