ATLAS ha osservato la diretta interazione del bosone di Higgs boson con il top quark

CERN and Bologna, Italy, 4 June 2018. The ATLAS Collaboration at CERN has announced the observation of Higgs bosons produced together with a top-quark pair. Observing this extremely rare process is a significant milestone for the field of High-Energy Physics. It allows physicists to test critical parameters of the Higgs mechanism in the Standard Model of particle physics.

The result exploits the full dataset delivered to ATLAS by the Large Hadron Collider (LHC) and establishes the signal with a statistical significance of 6.3 standard deviations. It concurs with a recent observation by the CMS Collaboration with a significance of 5.2 standard deviations using a smaller dataset. “This measurement constitutes a landmark achievement in the exploration of the Higgs mechanism and the interaction of Standard Model particles with the Higgs boson,” says Karl Jakobs, ATLAS Spokesperson. “It provides direct evidence that the heaviest known particle, the top quark, interacts with the predicted large strength with the Higgs boson.” The signal for this production has slowly built up over years of accumulating data, with first evidence reported by ATLAS last December.

As only 1% of all Higgs bosons are produced in association with top quarks, its observation was extremely challenging. ATLAS physicists examined five years of collision data to arrive at this result. “This was one of the most demanding searches ever carried out by the ATLAS Collaboration, requiring a concerted effort from several analysis teams,” says Fabio Cerutti, ATLAS Higgs working group convener. “As it is such a rare process, we had to look across many different Higgs boson decay channels. Some of these were limited by experimental uncertainties, while others by the quantity of the data we collected. It was only by combining all of these different analyses that we could achieve this observation.”