Green light for hunt for possible dark sexaquark particle

7 August 2023

Can six quarks make a stable particle that might form the dark matter in the universe? Nikhef physicist Patrick Koppenburg is going to find out in the coming years with an NWO ENW-M grant.

Dark matter is one of the greatest enigmas of modern physics. About 85 percent of all gravity in the universe cannot be explained by the visible matter in stars, nebulae and galaxies. If it is particles, they do not appear in the Standard Model of particle physics.

There are several ideas for the nature of dark matter, including so-called WIMPs and axions. Several experiments are searching for dark-matter particles from the cosmos, at Nikhef, for example, by XenonNT in Gran Sasso, Italy. But candidates for dark matter are also being sought at accelerators.

For Nikhef, Koppenburg is associated with the large LHCb experiment at the LHC accelerator at CERN, which, among other things, searches for differences between matter and antimatter. In the measurement data, however, there is also a constant search for unknown new particles.

Two views of a pentaquark: a connection of five quarks and antiquarks, or an interplay between two particles with two and three quarks.

In the process, earlier indications of short-lived compounds of four or five quarks have been found, leading to peaks in the measurement data from LHCb. Such tetra- or pentaquark resonances are not stable, and thus cannot possibly be dark matter in the universe.

In fact, researchers still question whether they are really particles, or compositions of particles with two or three quarks.

However, there are theoretical considerations as to why six quarks could give rise to a stable assembly that couples with other matter only via gravity. Koppenburg wants to try to find clues to this in the measurements with LHCb, together with a PhD student funded by NWO. This position has just opened up, and will close in September, Koppenburg said.

In this round in total NWO provides 18 ENW-M grants for researchers in curiosity driven fundamental projects.