The Higgs boson is associated with the Higgs field, which gives many fundamental particles their mass. Although it was predicted in the 1960s, it was not discovered until 2012. Since then, researchers have been studying whether the Higgs behaves exactly as predicted by the Standard Model of particle physics or whether it shows signs of physics beyond the Standard Model. This involves measuring how often Higgs bosons are produced, how they are produced, what they decay into, and how they interact with other particles.

In this work, the researchers combined measurements from proton-proton collisions recorded between 2016 and 2018 by the CMS experiment. These collisions can produce Higgs bosons, but such events are rare, so a huge dataset was needed. The study used 138 fb-1 of data, representing an enormous sample of proton-proton collisions on which to perform measurements of the Higgs. The researchers examined many Higgs decay channels, including decays into photons, bosons, and leptons. They also searched for invisible Higgs decays, in which the Higgs 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 researchers found that, with the current experimental precision, the Higgs boson behaves as predicted by the Standard Model. They 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 therefore 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.

This 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.

“It is amazing to see how far we have come in just over a decade since discovery. 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.” –  Dr Jonathon Langford from Imperial College London, a lead analyst for this paper.

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Prospects for Higgs physics at energies up to 100 TeV by Julien Baglio, Abdelhak Djouadi and Jérémie Quevillon (2016)