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Physicists Discover Strong Evidence of Four-Top Quark Production

Physicists Discover Strong Evidence of Four-Top Quark Production, Latest Science News
Event display of a candidate four-top-quark event, where two of the top quarks decay leptonically — one with a resulting muon (red) and one with an electron (green) — and two top quarks decay hadronically (green and yellow rectangles). The jets — b-tagged jets — are shown as yellow (blue) cones. Image credit: ATLAS Collaboration / CERN.

Physicists at the famed LHC at CERN have discovered strong evidence of 4-Top Quark production which is a rare process and occurs one in only 70000 pairs of top quarks created at LHC.

“The top quark is the most massive elementary particle in the Standard Model, clocking in at 173 GeV, which is equivalent to the mass of a gold atom,” the ATLAS physicists said.

“But contrary to gold, whose mass is mostly due to the nuclear binding force, the top quark gets all its mass from the interaction with the Higgs field.”

“So when four top quarks are produced in a single event, they create the heaviest particle final state ever seen at the Large Hadron Collider, with almost 700 GeV in total.”

In this search, the physicists studied four-top-quark productions and recorded the details between 2015-2018.

“When produced through proton-proton collisions at the Large Hadron Collider, this process leaves signatures in the ATLAS detector,” “The four top quarks produce four W bosons and four jets originating from bottom quarks.”

“The W bosons then, in turn, each decay into two jets or one charged lepton and an invisible neutrino.” “As a final step, the tau leptons decay into a lighter lepton or a jet, with additional neutrinos.” The physicists at LHC explained during the recent published article.

To achieve these results, the scientists chose to focus on collision events produced by two leptons with the same charge or 3 leptons of the same charge.

“We trained a multivariate discriminant using the distinct features of the signal, including the high numbers of jets, their quark-flavor origin, and the energies and angular distributions of the measured particles,” “The main background processes that resemble the signal stem from the production of a pair of top quarks in association with other particles, such as a W or Z boson, a Higgs boson, or another top quark.” They said.

The most difficult process during this event is the background process where A W Boson will be running with fake leptons.

“Fake leptons arise when the charge of a lepton is misidentified, or when leptons come from a different process but are attributed to the signal,” the scientists said. They continued saying “Both had to be well-understood and precisely evaluated in order to reduce the systematic uncertainty on the final result.” “We measured the cross-section for the production of four top quarks to be 24+7–6 fb, which is consistent with the Standard Model prediction (12 fb) at 1.7 standard deviations.”

“The signal significance amounts to 4.3 standard deviations, for an expected significance of 2.4 standard deviations were the four-top-quark signal equal to the Standard Model prediction. The measurement provides strong evidence for this process.”

The article has been released by CERN which was provided for press-release.