An international group of physicists in the ATLAS collaboration (CERN) discovered one of the rarest phenomena observed at the Large Hadron Collider. Scientists have reliably established the existence of weak scattering of vector bosons, which is expressed in the interaction between the particles-carriers of the weak interaction. This was announced in a press release on Phys.org.
The W and Z bosons are short-lived fundamental particles and belong to gauge bosons, which also include photons (carriers of electromagnetic interaction) and gluons, which carry strong interactions. There are two types of W boson that carry negative or positive electrical charges, and one type of Z boson that has no charge.
At the moment of collision of two protons, one quark of each emits a W or Z-boson, which, due to their large mass, cannot exist for a long time and quickly turn into other particles. Because of this, they have time to fly a distance that is only one tenth of the radius of the proton. In order for two bosons to interact, they must approach 1/500 of the radius of the proton. Such an event occurs approximately once every 20,000 billion proton-proton collisions.
Scientists recorded 60 events of weak scattering between the W ± and W ± bosons at an energy in the center of mass system (a system in which particles have equal and opposite momenta) equal to 13 teraelectronvolts. The probability that these events are random is less than 1 in 200 billion. This corresponds to a standard deviation of 6.9 sigma, which in particle physics is classified as a significant difference from background processes.
Physicists also pooled data from 2015-2016 to establish statistically significant scattering between W ± and Z bosons (with a standard deviation of 5.6 sigma).