The discovery of the Higgs boson in 2012 by the ATLAS and CMS experiments at CERN opened a phase of precision measurements of the properties of the Higgs boson, the keystone of the Standard Model (SM) of particle physics. In particular, the study of the Higgs boson pair production (HH) allows a parameter called Higgs boson self-coupling, the last one of the SM not yet measured, to be determined. This measurement provides a unique test of the mechanism that explains how particles acquire mass in the SM. The searches for HH production using data recorded between 2016 and 2018 set strong constraints on the HH production. By the use of advanced analysis methods, among other things, the study of this very rare process pushes the SM to its limits. The results have been published in several articles, including one in the journal Nature in June 2022.
The Higgs boson, discovered at Cern in 2012 by the ATLAS and CMS experiments, is the cornerstone of the Standard Model (SM) of particle physics. In the SM, the masses of individual particles are related to their interaction with the Brout-Englert-Higgs (BEH) field via a theoretical mechanism known as "symmetry breaking" and proposed more than 50 years ago by the theorists Brout, Englert and Higgs. The Higgs boson (H) itself results from this mechanism and its discovery in 2012 was, therefore, a strong indication of the validity of this theoretical construct. Subsequently, various measurements of the Higgs boson's interactions with other SM particles such as the weak bosons Z, W and the heavy fermions (b, t quarks, tau leptons) confirmed the SM predictions proposed by Glashow, Salam and Weinberg in 1967.
The cosmic background neutrino is one of the predictions of the standard cosmological model, but it has never been directly observed. These so-called "relic neutrinos" could be captured on a radioactive nucleus like tritium. The resulting capture rate depends on the local density of relic neutrinos. Since massive neutrinos get caught by the gravitational potential of our galaxy and cluster locally, a modest local overdensity of relic neutrinos should exist on Earth. More exotic considerations could lead to more substantial overdensities. The KATRIN experiment published in June 2022 in Physical Review Letters its first search for relic neutrinos based on analysis of data recorded in 2019. The analysis, led by an IRFU physicist, improves on previous limits by two orders of magnitude.
The KATRIN collaboration has just recently reported a new upper limit of 0.8 eV/c2 on the mass of neutrinos. The KATRIN spectrometer also has a strong potential to search for new, so-called "sterile" neutrinos, based on a fine analysis of the tritium beta decay spectrum. The collaboration has just published its new results in Physical Review D based on the first two data campaigns acquired in 2019. This work reveals no evidence of a fourth neutrino, and KATRIN may well be a key player in clarifying the anomalies observed by some neutrino oscillation experiments over the past 20 years or so.
The KATRIN (KArlsruhe TRItium Neutrino Experiment) located at the Karlsruhe Institute of Technology (KIT) has just crossed a symbolic threshold. In a paper published in the prestigious journal Nature Physics, the collaboration reveals a new upper limit of 0.8 eV/c^2 for the mass of neutrinos. This result is of fundamental interest for both particle physics and cosmology.
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Dernière mise à jour : Nov 19th, 2024
