Lepton Flavor Violation in $\tau \to 3 \mu$ with LHCb

Thursday 7 May 2026, 11:00 → 13:00 Europe/Zurich

4/2-011 - TH common room (CERN)

Abstract
A direct discovery of lepton flavor violation (LFV) at colliders would be a smoking gun for new physics, since such processes are highly suppressed in the Standard Model. In this talk, LFV transitions in tau decays will be discussed, with a particular focus on τ→μ channels. The first part will introduce the theoretical framework, including the main phenomenological motivations and representative new physics scenarios that can lead to observable effects. The second part will present the recent results from the LHCb experiment on the search for the decay τ→μμμ, focusing on the determination of the upper limit on its branching fraction using Run 2 data, and discussing the prospects for improved sensitivity in Run 3.

Speakers

Giulia Frau 

I completed my undergraduate studies at the University of Cagliari and obtained my PhD from Heidelberg University in summer 2023, with a thesis titled “Search for the tau->mumumu decay at the LHCb experiment”. Since March 2024, I have been a postdoctoral research associate in the LHCb group of the University of Manchester, fully based at CERN. Since 2026, I have served as convener of the Very Rare Decays sub-working group. Besides very rare decay analyses, I also work on the ASLD analysis, focusing on CP violation measurements in B0-B0bar mixing. Finally, I coordinate alignment and online calibration activities for the 2026 data-taking. 

 

Marco Ardu 

My research focuses on beyond the Standard Model phenomenology, with a particular interest in low-energy precision observables. I completed my undergraduate studies at the University of Pisa and obtained my PhD in Montpellier under the supervision of Sacha Davidson, with a thesis on effective field theories and lepton flavour violation. I am currently finishing my first postdoctoral position at the Instituto de Fisica Corpuscular (IFIC) in Valencia, and I will soon begin my second postdoc at the Instituto Nazionale di Fisica Nucleare (INFN) in Padova.