On July 4, 2012, physicists from the ATLAS and CMS collaborations at CERN’s Large Hadron Collider announced the observation of a Higgs boson with a mass of about 125 gigaelectronvolts. Ten years later, and with data corresponding to the production of 30 times more Higgs bosons, ATLAS and CMS researchers know much more about the properties of the elementary particle. Their results, presented in two articles published in the journal Nature, show that the properties of the particle are remarkably consistent with those of the Higgs boson predicted by the Standard Model of particle physics. They also show that the particle is increasingly becoming a powerful means of searching for new, unknown phenomena which, if discovered, could help unravel some of physics’ greatest mysteries, such as the nature of mysterious dark matter. present in the Universe. .
The Standard Model of particle physics describes the known fundamental particles and forces that make up our universe, with the exception of gravity.
One of the central features of the Standard Model is a field that permeates all of space and interacts with fundamental particles.
The quantum excitation of this field, known as the Higgs field, manifests itself through the Higgs boson, the only fundamental spinless particle.
In 2012, a particle with properties compatible with the Higgs boson was observed by the ATLAS and CMS experiments at the Large Hadron Collider (LHC).
Since then, more than 30 times as many Higgs bosons have been recorded by the experiments, allowing much more precise measurements and new tests of the theory.
“The Higgs boson is the particle manifestation of an ubiquitous quantum field, known as the Higgs field, which is fundamental to describing the Universe as we know it,” the physicists said.
“Without this field, elementary particles such as the quarks that make up the protons and neutrons of atomic nuclei, as well as the electrons that surround the nuclei, would have no mass, nor would the heavy particles (W bosons) that carry the charged weak force, which initiates the nuclear reaction that powers the Sun.
To explore the full potential of LHC data for studying the Higgs boson, including its interactions with other particles, ATLAS and CMS have combined many complementary processes in which the Higgs boson is produced and decays. into other elementary particles.
Each of their complete LHC Run 2 datasets (between 2015 and 2018) includes over 10 trillion proton-proton collisions and around 8 million Higgs bosons.
The studies each combine an unprecedented number and variety of Higgs boson production and decay processes to obtain the most precise and detailed set of measurements to date of their rates, as well as the strength of the interactions. of the Higgs boson with other particles.
All measurements are remarkably consistent with Standard Model predictions within a range of uncertainties depending, among other criteria, on the abundance of a given process.
For the interaction strength of the Higgs boson with the carriers of the weak force, an uncertainty of 6% is reached.
For comparison, similar analyzes with the full data sets from Trial 1 resulted in a 15% uncertainty for this interaction strength.
“After only ten years of exploring the Higgs boson at the LHC, the ATLAS and CMS experiments have provided a detailed map of its interactions with force carriers and matter particles,” said Spokesperson Dr Andreas Hoecker. of the ATLAS collaboration.
“The Higgs sector is directly related to very deep questions related to the evolution of the early Universe and its stability, as well as the mass-hitting pattern of particles of matter.”
“The discovery of the Higgs boson has triggered an exciting, deep and broad experimental effort that will span the entire LHC program.
“Drawing such a portrait of the Higgs boson so soon was unthinkable before the LHC started operating,” said CMS spokesperson Dr Luca Malgeri.
“The reasons for this success are manifold and include the outstanding performance of the LHC and the ATLAS and CMS detectors, as well as the ingenious data analysis techniques employed.
The new combined analyzes also provide, among other new results, strict bounds on the interaction of the Higgs boson with itself and also on new, unknown phenomena beyond the Standard Model, such as the decay of the Higgs boson into invisible particles that can constitute dark matter.
ATLAS Collaborative. A detailed map of the Higgs boson interactions by the ATLAS experiment ten years after the discovery. Nature, published online July 4, 2022; do I: 10.1038/s41586-022-04893-w
CMS Collaborative. A portrait of the Higgs boson by the CMS experiment ten years after the discovery. Nature, published online July 4, 2022; do I: 10.1038/s41586-022-04892-x