Musing with Muons: From Light New Physics at Mu3e to Neutron Star Dynamics

• Toby Opferkuch

Room: Aula D In this talk, I'll delve into recent work centred on muons, highlighting developments in two key areas: the Mu3e experiment's search for light new particles and the study of muon behaviour in neutron stars. I'll discuss how the Mu3e experiment is uniquely positioned to search for light new physics through resolving colinear electrons and positirons. For promptly decaying new resonances this allows Mu3e to probe a difficult corner of parameter space for dark photons and axion-like particles. While for long-lived new resonances I'll show how a new search strategy, requiring an additional e+ e- pair from internal conversion, can be used to circumvent the calibration challenges which plague the μ → e+X channel for X ≲ 20~MeV. At the end turning to astrophysics, I'll talk about the intriguing role of muons in neutron stars, where their interaction dynamics offer insights into the neutron stars' internal processes potentially leading to a non-thermal MeV-scale flux of neutrinos.

Jet bundle geometry of scalar field theories

• Ilaria Brivio (Istituto Nazionale di Fisica Nucleare)

Room: Aula D

QCD Axion: Some Like It Hot

• Mauro Valli (Istituto Nazionale di Fisica Nucleare)

Room: Aula D The QCD axion is one of the most compelling targets for physics beyond the Standard Model, offering a characteristic imprint in the Early Universe as a hot relic. In this talk we derive a state-of-the-art bound on the QCD axion from Cosmology by confronting momentum-dependent Boltzmann equations against up-to-date measurements of the CMB – including ground-based telescopes – and abundances from BBN. We conclude presenting forecasts using dedicated likelihoods for future cosmological surveys, and exploiting recent results on non-perturbative thermal rates at the crossover from lattice QCD.