Physics at the intensity frontier

The RICH detector at CERNʼs NA62 experiment, which searches for extremely rare kaon decays using highly intense beams. Photo: J.Pinzino

Reprinted from the CERN Courier, May 2017, “Faces and Places”

The Standard Model of particle physics has proved to be a consistent description of natureʼs fundamental constituents and their interactions, and its predictions have been confirmed by numerous experiments, most recently with the discovery of the Higgs boson at the LHC. However, the model fails to explain several phenomena in particle physics, astrophysics and cosmology, and it is expected that yet unknown particles or interactions are needed to explain these puzzles.

Our inability to observe new particles possibly lies in their extremely feeble interactions. If true, this would imply that experiments are needed not just at the high-energy frontier but also at the “intensity frontier”, by increasing the number of collisions to search for rare events. In 2016, CERN created a Physics Beyond Colliders study group with a mandate to explore opportunities offered by the CERN accelerator complex to address outstanding questions in particle physics through projects complementary to high-energy colliders (CERN Courier November 2016 p28).

A two-week-long “theory institute” took place at CERN from 20 February to 3 March to discuss the theory and phenomenology of possible new physics at low energy scales. More than 100 participants from 21 countries discussed the theoretical landscape, predicting new light particles and “dark forces”. The potential for the new physics reach of existing and planned intensity-frontier experiments – SHiP, NA62, DUNE, MATHUSLA and many others – was discussed. These future experiments are at different stages today, ranging from the preparation of a comprehensive design report (SHiP) to a letter of intent (MATHUSLA). The time is therefore ripe to ensure that any necessary changes to the experiment designs can still be made to the physics reach of intensity-frontier experiments.

The RICH detector at CERNʼs NA62 experiment, which searches for extremely rare kaon decays using highly intense beams.