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Josh McFayden (LBNL) “Unravelling LEP-Era Lepton Flavour Universality Discrepancy with ATLAS”

July 21, 2020 @ 12:00 pm - 1:00 pm


A remarkable feature of the Standard Model (SM) is that each lepton flavour (electron, muon, tau) is equally likely to interact with a W boson. This is known as Lepton Flavour Universality.

In a recent ATLAS measurement, a novel technique using events with top-quark pairs has been exploited to test the ratio of the probabilities for tau leptons and muons to be produced in W boson decays, R(τ/μ).

In the SM, R(τ/μ) is expected to be unity, but a longstanding tension with this prediction has existed since the LEP era, where, from a combination of experiments, R(τ/μ) was measured to be 2.7σ higher than the SM expectation.

If the LEP result were confirmed to O(1%) precision it would correspond to an unambiguous discovery of beyond the SM physics. This latest ATLAS measurement obtains this level a precision – please join the RPM to discover whether or not it agrees with LEP!


If you are looking to confirm if there is an event, due to room reservation, please go to RPM website for a list of all scheduled talks.
Troy Cortez is inviting you to a scheduled Zoom meeting.

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Meeting ID: 959 0640 5235
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Meeting ID: 959 0640 5235



July 21, 2020
12:00 pm - 1:00 pm


Zoom Talk
Berkeley, ca 94720
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