Physicists from the ATLAS project compared the rate at which taons and muons are produced in this process.
It turned out that taons and muons are formed equally within the measurement error – this agrees with the axiom of the Standard Model about lepton universality and eliminates the disagreement with the theoretical prediction that was observed in a similar analysis eight years ago.
We have carried out the most accurate measurements of this kind, showing that the behavior of taons and muons coincides by 99.2%. This result is fully consistent with the predictions of the Standard Model and indicates that the results of similar measurements at the LEP collider, which indicated the presence of new physics, were the result of random fluctuations.
This casts doubt on the fact that violations of the universality of lepton interactions do exist. Most likely, hints of this appeared due to the insufficient amount of data collected during past experiments at the LHC and LEP.
In the Standard Model, leptons are fundamental particles with half-integer spin that do not participate in strong interactions. Three generations are distinguished among leptons, each of which consists of an electrically charged particle and its neutral partner, the neutrino.
- First generation: electron.
- Second: muon.
- Third: heavy taon.
Physicists of the ATLAS collaboration with the participation of Andreas Hoecker from CERN have specified the production rates of muons and taons in W-boson decays at the LHC detector of the same name. For the analysis, they used data from proton-proton collisions with an energy of 13 teraelectronvolts in the center of mass system, which the detector collected from 2015 to 2018.