A measurement of a essential principle of the standard design of particle physics—lepton flavour universality—captured by the ATLAS detector at the Substantial Hadron Collider, is reported in a paper revealed in Character Physics.
The findings supersede the extensive-standing end result from the Substantial Electron–Positron Collider.
Our understanding of elementary particles—the constructing blocks of the Universe—and the electromagnetic, weak and powerful basic forces that act involving them, is formulated in the conventional product of particle physics. In the concept, electrons, muons and τ leptons signify 3 versions (or flavours) of an electrically charged form of elementary particle acknowledged as leptons. The typical design assumes that the power of the couplings concerning leptons and the particles that mediate the weak force—known as ‘W’ or ‘Z’ electroweak gauge bosons—is independent of the lepton flavour. This very long-held theory, known as lepton flavour universality, has just lately been challenged by experiments at B-factories and at the LHC.
The ATLAS Collaboration—involving a international team of scientists like experts from Lancaster –studied no matter whether this ‘universal truth’ retains genuine for the muon and the τ lepton in about fifty percent a million proton–proton collisions recorded with the ATLAS detector at the Huge Hadron Collider. By analyzing decays of W bosons into τ leptons and muons and measuring the ratio of their decay costs, the authors were being ready to conclude that the weak drive interacts with both of those types of lepton in the similar way.
This outcome from the ATLAS Collaboration is the most precise measurement to date, with pretty much twice the precision attained from experiments at the Significant Hadron Collider’s predecessor at CERN—the Massive Electron–Positron Collider (LEP).
Lancaster University Physics Professor Guennadi Borissov said: “The measurements at LEP indicated that there may well be a difference among the decays to unique kinds of leptons. This intriguing trace of deviation from the common product has been unconfirmed for about 20 yrs. While our newest measurements do not back up the final result of the LEP, it has been fascinating to come across a new and remarkably exact way to exam this making use of the electric power of the Big Hadron Collider, with Lancaster becoming at the coronary heart of each move of the examination.”
Professor Roger Jones, head of the Lancaster ATLAS team, explained: “Exams these as ours of basic theoretical assumptions are at this time a warm region of investigate in particle physics. Current final results from the LHCb experiment, and incredibly precise measurements of muons manufactured by the g-2 collaboration (which also has Lancaster physicists in the workforce) have supplied new hints that leptons could not all behave the exact same way as our theories forecast.
“In distinction, new and really precise measurements present that in essential approaches the leptons seriously do behave the very same way. It will be exciting to see if the hints from other experiments turn out to be clear proof. If so, theories will have to account for our powerful proof for leptons behaving in the same way in the process we have studied and however behaving otherwise in other procedures.”
Lengthy-standing tension in the Conventional Design addressed
Examination of the universality of τ and μ lepton couplings in W-boson decays with the ATLAS detector, Nature Physics (2021). DOI: 10.1038/s41567-021-01236-w
Scientists explore assistance for disputed universal truth of particle physics (2021, July 6)
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