New results from the CMS and ATLAS collaborations prove couplings between the Higgs boson and the heaviest elementary particle known, the top quark.
Interviews with ATLAS and CMS physicists on new results that show that the top quark acquires its mass from the Higgs field.
According to the Standard Model, the more a particle interacts with the Higgs boson - or more precisely with the invisible quantum field from which the boson arises - the heavier the particle is. The top quark, being the heaviest elementary particle known, should therefore have the largest interaction strength with the Higgs field. This interaction strength can be directly probed by looking at how often a Higgs boson is produced together with a pair of top quarks. But this process, known as ttH production, isn't easy to measure. For one, it's rare: its likelihood, or cross section, is only 1% of the total cross section for producing the Higgs. For another, the Higgs and the top quarks decay into other particles in many complex ways, or modes.
The latest studies from the CMS and ATLAS teams were presented in Bologna at the sixth annual Large Hadron Collider Physics conference,. Using data from proton-proton collisions collected at an energy of 7, 8, and 13 TeV, the CMS team performed several independent searches for ttH production, each targeting a different Higgs-decay mode (W bosons, Z bosons, photons, τ leptons, and bottom quark jets). To maximise the sensitivity to the sought-after ttH signal, the researchers then combined the results from all of the searches, finding an excess of decay events over the "no-ttH-production" hypothesis with a statistical significance of more than five standard deviations (five sigma) - the gold standard of proof for a discovery in particle physics. What's more, the result is consistent with the Standard Model prediction for ttH production.
The ATLAS researchers did a similar analysis, targeting some of the Higgs-decay channels probed by CMS and other and combining them to boost the sensitivity to the ttH signal. They too found an excess of events.
In addition to representing the first observations of a new way in which the Higgs boson can be produced (with a pair of top quarks), the new findings by CMS and ATLAS show that the Higgs boson interacts with the top quark with a strength that is consistent with that predicted by the Standard Model.
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1 окт 2024
