Lepton flavour change in nuclei

Aula Renzo Leonardi - Villa Tambosi

Str. delle Tabarelle, 286, 38123 Villazzano TN
Villazzano

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The observed neutrino masses imply that contact interactions where charged leptons change flavour must occur. And μ → e conversion can probe such contact interactions to a smaller branching ratio than any other process.
When a μ stops in a target, it can be captured by the nuclei, and tumble down to the 1s state. It can then decay (→ eν̄ν), exchange a W with a nucleon, or transform to an e− which escapes with all the available energy, via a wide variety of interactions (with the electromagnetic field, pions or nucleons). This electron of precisely defined energy is the experimental signature that allows upcoming/planned experiments to aim for conversion rates of 10^−16/10^−20× the muon decay rate (the current limit is ∼ 10^−12). And despite that only the e− is observed, the lepton-flavour-changing interaction (eg dipole, spin-dependent,…) could be identified from the rates on different nuclei.
The theoretical challenge is to accompany this exceptional leap in experimental sensitivity. The calculation involves physics at many scales, from heavy New Physics to nuclear, so the involvement and collaboration of various theoretical communities (nuclear, BSM, χPT…) is required. There have been recent attempts to improve the theoretical state of the art, so the aim of the workshop is to understand what has been done, what needs to be done, and what can be done. And then, hopefully, be the place where collaborations are born. Europe has a long-standing expertise in nuclear physics and particle phenomenology, and ideally our workshop could contribute to attracting younger members of the community to μ → e calculations.

The workshop aims to:
(1) Summarize the ”state of the art” techniques for calculating μ → e conversion.
(2) Initiate the construction of a common space, and vocabulary, among the theory communities involved, so as to
(3) quantify the theoretical uncertainties of μ → e rate computations, and identify where the accuracy can be improved.
(4) Facilitate collaborations among participants aiming to perform improved μ → e rate computations.
Another important goal is to involve experimentalists, so as to understand the theoretical input required by the initial stages of μ → e conversion experiments (which plan Aluminium targets), and also to explore, in the case of a discovery, complementary palettes of targets that could allow to distinguish among lepton flavour changing interactions.
Finally, we aim to attract younger members of the community to this topic, so we envisage to invite the senior invitees to propose the names of junior collaborators who could accompany them or replace them at the workshop.

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Organizers

  • Karim Bennaceur (Université Claude Bernard Lyon 1, IP2I, IN2P3)
  • Sacha Davidson (LUPM, IN2P3)
See complete details and information

Registration

Registration available from 14/02/2025 until 21/03/2025.

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