Geneva, 23 June 2025. CERN is welcoming Slovenia as its 25th Member State, opening a new chapter in a partnership that stretches back three decades.

“Slovenia’s full membership in CERN is an exceptional recognition of our science and researchers,” said Dr Igor Papič, Slovenia’s Minister of Higher Education, Science and Innovation. “Furthermore, it reaffirms and strengthens Slovenia’s reputation as a nation building its future on knowledge and science. Indeed, apart from its beautiful natural landscapes, knowledge is the only true natural wealth of our country. For this reason, we have allocated record financial resources to science, research and innovation. Moreover, we have enshrined the obligation to increase these funds annually in the Scientific Research and Innovation Activities Act.”

“On behalf of the CERN Council, I warmly welcome Slovenia as the newest Member State of CERN,” said Costas Fountas, President of the CERN Council. “Slovenia has a longstanding relationship with CERN, with continuous involvement of the Slovenian science community over many decades in the ATLAS experiment in particular.”

“Slovenia and CERN have been collaborating closely for more than 30 years, and I am delighted to welcome Slovenia to the group of CERN Member States,” said Fabiola Gianotti, CERN Director-General. “I am sure that tighter bounds will be mutually beneficial to CERN and Slovenia.”

Slovenian physicists contributed to the CERN programme long before Slovenia became an independent state in 1991, participating in an experiment at the Low-Energy Antiproton Ring (LEAR) and in the DELPHI experiment – part of CERN’s previous large accelerator, the Large Electron–Positron collider (LEP). In 1991, CERN and the Executive Council of the Assembly of the Republic of Slovenia concluded a Cooperation Agreement concerning the further development of scientific and technical cooperation on CERN research projects.

In recent years, Slovenian physicists have been participating in the ATLAS experiment at the Large Hadron Collider (LHC).Their activities range from research and development, to construction and commissioning, and the harvesting of physics results. At the Slovenian Tier 2 data centre in Ljubljana, which is part of the Worldwide LHC Computing grid, the focus has been on silicon tracking, protection devices and computing. Slovenian scientists and students have had leading roles in several physics analyses, concentrating on identifying signals that would point to physics beyond the Standard Model.

Currently, Slovenia is heavily involved in projects to upgrade the ATLAS detector for the High-Luminosity LHC, especially the upgrade of the beam conditions monitor and the silicon strip part of the inner tracker, as well as the novel High-Granularity Timing Detector.

As a CERN Member State, Slovenia will have voting rights in the CERN Council, the Organization’s highest decision-making authority. Membership will also enhance opportunities for Slovenian nationals to be recruited by CERN and for Slovenian industry to bid for CERN contracts.