The most comprehensive study of the Higgs boson to date has found that the particle behaves exactly as the Standard Model of particle physics predicts, significantly narrowing the search for new physics beyond current theory. The analysis, conducted by the CMS Collaboration at the Large Hadron Collider, combined measurements from proton-proton collisions recorded between 2016 and 2018 and examined a wide range of Higgs production and decay processes.
The Higgs boson is associated with the Higgs field, which gives many fundamental particles their mass. Although its existence was predicted in the 1960s, it was not discovered until 2012. Since then, researchers have been testing whether the particle behaves precisely as theory dictates or whether it shows signs of deviation that could point to undiscovered particles or forces.
The new study used 138 inverse femtobarns of collision data, an enormous sample that was necessary because Higgs bosons are produced only rarely in proton-proton collisions. The researchers examined many Higgs decay channels, including decays into photons, bosons, and leptons. They also searched for invisible Higgs decays, in which the particle would produce undetectable particles such as dark matter candidates, and studied rare off-shell Higgs production, where the Higgs is produced as a virtual state with a mass different from its physical mass.
The team measured an overall Higgs signal strength of 1.01 ± 0.05, where a value of 1 represents perfect agreement with the Standard Model. The result is fully consistent with theoretical expectations. Many theories that extend the Standard Model predict that undiscovered particles or forces could subtly alter how the Higgs boson is produced or how it decays. Because the CMS measurements agree with Standard Model predictions, there is currently little evidence for such effects, significantly constraining many proposed theories of new physics.
«It is amazing to see how far we have come in just over a decade since discovery,» said Dr Jonathon Langford from Imperial College London, a lead analyst for the paper. «We are now able to measure the Higgs boson production rate at the LHC with a 5% precision, confirming our theories regarding the origin of mass in the Universe.»
The study provides the most comprehensive test of the Higgs boson to date using data from the CMS experiment. By narrowing the range of possible deviations from the Standard Model, it helps guide future searches for new physics at the Large Hadron Collider and other particle physics experiments. The findings were published in Reports on Progress in Physics.
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