On the Particle Physics Horizon, a New Supercollider Comes Into Focus

At 80 to 100 kilometers in circumference, the future supercollider, located near the LHC at the Swiss-French border, would dwarf its record-holding counterpart. Credit: CERN

By Korena Di Roma Howley

In a 100-kilometer leap for particle physics, the governing body of European lab CERN recently approved taking additional steps toward plans to build a $24-billion supercollider that will measure the properties of the Higgs boson particle. A major component of the standard model of particle physics, the once elusive particle was first discovered in 2012 via CERN’s Large Hadron Collider (LHC), currently the world’s largest particle accelerator at 27 kilometers in circumference.

The next-generation accelerator would require a tunnel 80 to 100 kilometers in circumference and would be the first of two machines planned for space. This first collider would function as a so-called Higgs factory that would churn out the particles in a clean environment, enabling high-precision measurements and potentially allowing physicists to push the boundaries of the standard model. If built, the collider would make use of existing infrastructure for the LHC, located at the Swiss-French border near Geneva, Switzerland.

Though it wouldn’t be as efficient as a linear electron-positron collider, a circular tunnel could later house a second machine, a more powerful high-energy proton collider. This would be constructed, if the necessary technology exists, in the latter half of the century.

Meanwhile, CERN’s participation in the proposed International Linear Collider—which will potentially be hosted by Japan—remains a possibility, and this decade will see the unveiling of the High-Luminosity LHC, a major upgrade that’s currently in progress at the particle physics lab.

The decision to move ahead with a technical and financial feasibility study for the electron-positron smasher stops short of a formal approval but does mean that plans for its design and funding will take center stage in the coming years. Since the cost would exceed what the member nations contribute to CERN’s regular budget, additional funds would likely have to come from outside Europe and represent a global effort.

The announcement of the plan was part of the 2020 update of the European Strategy for Particle Physics compiled by the European Strategy Group, a body established by the CERN Council. The strategy identified the study of the Higgs boson as one of the highest scientific priorities for European particle physicists, along with the exploration of the high-energy frontier. “These are two crucial and complementary ways to address the open questions in particle physics,” said CERN in its June 19 press release.

If plans for the new collider are ultimately approved, construction isn’t expected to begin for another two decades or so. In the meantime, the LHC we know and love will continue to help increase our understanding of the particle universe. On June 30 scientists studying data from the LHCb collaboration announced in a preprint the discovery of a new exotic particle, a tetraquark made up of four of the same type of heavy quark—two charm quarks and two charm antiquarks. Though key properties of the particle are yet to be confirmed, the discovery will enable scientists to better understand and further study the binding mechanisms of composite quarks and will, according to CERN, likely represent the first in a new class of particles.