Experimental Particle and Astro-Particle Physics Seminar

Monday 26 Apr 2021, 14:00 → 16:00 Europe/Zurich

Florencia Canelli (Universitaet Zuerich (CH))

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 and, especially with well publicised recent results from LHCb on R_K, is a very high profile area of particle physics research.

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 and the latest ATLAS measurement obtains this level a precision - please join the seminar to discover whether or not it agrees with LEP!

 

Zoom room link

Meeting ID: 912 1383 7955
Passcode: 069577
 

14:00 → 15:00 Unravelling LEP-era Lepton Flavour Universality discrepancy with ATLAS

Speaker: Josh McFayden (University of Sussex)

2021-04-26_ZurichSeminar_ttLFU_mcfayden.pdf