LHCb collaboration observes CP violation in baryons for the first time
The standard model of particle physics predicts that particles and antiparticles behave differently – this results from so-called CP violation. Researchers at the LHCb detector at CERN have now been able to demonstrate this behaviour for the first time in so-called baryons, i.e. particles consisting of three quarks. The LHCb experiment is one of four experiments at the Large Hadron Collider at CERN, which is funded in Germany by a research priority of the Federal Ministry of Research.
At this year's "Recontres de Moriond" [1] conference, the LHCb collaboration was able to announce a major success:
Researchers from the collaboration succeeded for the first time in demonstrating so-called CP violation, i.e. the different behaviour of matter and antimatter in baryons. They reported this in a lecture at the Moriond Conference in the French Alps. At the same time, the result was submitted to the renowned scientific journal Nature for publication.
Baryons are particles composed of three quarks. The best-known representatives are the proton and the neutron, which make up the nuclei of atoms. However, there are many other such particles. In one of them, the so-called Λb0 particle and its antiparticle, it has now been possible for the first time to detect this CP violation in baryons.
This measurement is of great significance in several respects: on the one hand, it shows once again that the mechanisms of CP violation described by the standard model of particle physics appear to apply universally. It is therefore a further impressive confirmation of the validity of the standard model. However, the researchers are also fascinated by another aspect:
"The really exciting thing is that for the first time we are really measuring matter-antimatter asymmetries, as we can clearly say which of the particles is matter and which is antimatter.
With the mesons [in which CP violation has been measured so far, editor's note] this is not so clear, they each have a quark and an antiquark and the definition of what is a meson or antimeson is arbitrary," explains Prof Stephanie Hansmann-Menzemer, Spokesperson of the German LHCb research priority and member of the LHCb collaboration.
The fact that this measurement is now possible is primarily due to the large number of collisions that have been recorded at the LHC in recent years, allowing researchers to achieve a previously unattainable level of measurement accuracy. The researchers are now looking forward to further utilizing this data in order to maybe find a deviation from standard model predictions with even greater precision and thus perhaps solve one of the great mysteries of particle physics, such as the existence of dark matter.
More information:
Press release of the LHCb collaboration
CERN press release