At CERN in Geneva, a rare form of decay of the Higgs boson has been observed for the first time which, if confirmed, could provide indirect evidence of still unknown particles, not foreseen by the standard theory of physics: in particular, the Atlas and Cms experiments they were able to see, by joining forces, the Higgs boson turning into a pair formed by a photon, the particle of light, and a Z boson, the 'heavy' brother of the photon.
The result was presented by the Atlas and CMS experiments at the LHC Physics Conference, which was held in Belgrade from 22 to 26 May. "This is an important step forward to understand the rare phenomena related to the Higgs boson," Roberto Tenchini of the National Institute of Nuclear Physics, president of the National Scientific Commission 1 for particle physics, told ANSA. "It indicates that the sensitivity of experiments is increasing more and more – adds Tenchini – making it possible to observe events of this type, fundamental because they can be clues of a new physics or can be further confirmations of the one we know".
Researchers from the Atlas and CMS experiments joined forces to try to maximize the results obtained separately during the second phase of LHC data taking, which took place between 2015 and 2018: the collaboration, in fact, significantly increased the statistical accuracy and scope of the analyzes, although the observation cannot yet be confirmed on the basis of these data. For confirmation, we will have to wait for the data collection in progress, thanks to the third cycle started in recent months: "I think that within a couple of years, by 2025, we will have the data we need", comments Roberto Tenchini, who contributed to the construction of CMS and was national manager of the experiment from 2015 to 2017.
Another observation, this time confirmed, that could hold the key to a new physics had been presented in March 2023 always by the two joint experiments: "In that case the simultaneous production of four top quarks was observed – says Tenchini – an even more interesting rare phenomenon". The top quark is by far the most massive elementary particle, with a mass approaching that of the atomic nucleus of gold, and is therefore the particle that has the strongest bond with the Higgs boson. The production of four top quarks is very rare, because they usually occur in pairs of quarks and antiquarks (quark antiparticles), and also very difficult to detect. "It is significant that two experiments that normally collect data independently, and are therefore in competition with each other, can also collaborate to try to learn something more."
