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70 years of theoretical physics at CERN


Theory seminar in 1962
CERN theorists Prentki, D'Espagnat, and Amati following a seminar in 1962 (Image: CERN)

CERN is quiet during the summer months, but there is one place that breaks that rule: the corridors of the CERN Theoretical Physics department. Here, the finest minds in theoretical physics gather all year round to discuss models and recent findings with colleagues, creating the vibrant atmosphere that has made it so special since its early days, 70 years ago. This environment not only complements the experimental research conducted within the Organization, but the overarching aim – describing nature’s laws – is an intellectual pursuit in itself. Physicists leaving the Theoretical Physics department remain connected and carry this mindset wherever they go, as was the intention of the original founders, preserved and cultivated to this day by the department’s staff.

The Theory Study Group

During the post-war era, bringing together people from different countries around ambitious scientific projects became one of many ways of preserving and consolidating the newly found peace in Europe. Inspired by this idea, the provisional CERN Council, during its first session in May 1952, founded the Theory Study Group as one of four study groups tasked with planning a unique laboratory. Headed by Niels Bohr and located at the Institute for Theoretical Physics in Copenhagen, the Group set out to turn the vision imagined by the founders of CERN into a reality. Three pillars were envisaged for this Group: conducting studies and research related to high-energy physics, establishing collaborations based on existing instruments in Europe and, finally, planning new collaborations on the continent.

Following this blueprint, the Theory Study Group interacted with its experimental physics counterparts to think up the first CERN accelerators. In parallel, it conducted its own research to provide scientific input to the provisional Council. One of its first activities, preceding the second session of the provisional Council, was to host a conference at the Institute in Copenhagen, where the physicists present shifted the focus from nuclear to elementary particle physics due to the discovery of kaons in cosmic rays a few years earlier – a shift that would shape CERN’s identity for the decades to come. Moreover, other conferences, training programmes and visits to European institutes helped the theorists take their open-mindedness out into the world and strengthened relationships and collaborations between scientists, even before the final location for CERN was chosen or its convention was signed.

From Copenhagen to Geneva

After the provisional Council chose Geneva as the location for CERN, the Theory Study Group moved to CERN from 1 October 1957, joining the theorists who had already started working in Geneva three years earlier. Many of the findings they made in this period have entered today’s textbooks.

Since 1957, CERN has been the heart of both experimental and theoretical high-energy physics worldwide. Many physicists who shaped the landscape of theoretical high-energy physics were at one time affiliated in some capacity with the CERN Theoretical Physics department, including four former CERN Directors-General.

Ahead of its time

In many regards, the current state of particle physics research is similar to that when the Theoretical Physics department began. In the 1950s, many particles had been discovered and it then took almost two decades of extensive research before that range of particles was organised into a consistent picture – the Standard Model of particle physics.

Nowadays, the Standard Model of particle physics provides that consistency but comes short of describing the physics at higher energy scales, driving theoretical physicists to develop new models explaining this new physics.

“70 years later, theorists in the Theoretical Physics department still share the same ideals that inspired the foundation of the CERN Theory Study Group,” says Gian Giudice, head of the Theoretical Physics department. “We want to bring together theorists from all over the world in a research environment where everyone’s creativity and talent can flourish, in the name of science, peace and cooperation.”