Contributor info: Dr Pablo Roig

Pere Masjuan, Alejandro Miranda, Pablo Roig

SciPost Phys. Proc. 17, 023 (2025) · published 23 July 2025 | Toggle abstract · pdf

We review the $\tau$ data-driven computation of Euclidean windows for the hadronic vacuum polarization contribution to the muon anomalous magnetic moment ($a_\mu$), which agree with the lattice results, making the difference of the $e^+e^-$ data-driven methods with them more intriguing. This conundrum needs to be solved by next year, when the final FNAL $a_\mu$ measurement will be published, in order to extract firm conclusions on possible new physics effects.

Jesús Alejandro Miranda Hernández, Pablo Roig Garcés

SciPost Phys. Proc. 16, 032 (2025) · published 15 July 2025 | Toggle abstract · pdf

We revisit the radiative corrections to the $\tau^-\to\pi^-\pi^0\nu_\tau(\gamma)$ decays using Resonance Chiral Theory for the structure-dependent part. This channel is the most important one to understand the hadronic vacuum polarization piece of the muon g-2, which dominates the uncertainty of its data-driven prediction in the Standard Model. Using our results, the discrepancy between theory and experiment for this observable is reduced to $\sim2.2\sigma$.

Alejandro Ibarra, Marcela Marín, Pablo Roig

SciPost Phys. Proc. 16, 011 (2025) · published 14 July 2025 | Toggle abstract · pdf

The $\ell_i\to\ell_j\chi$ decays, with $\chi$ a boson associated to the $U(1)_\chi$ symmetry, have not been described satisfactorily so far for light spin-one $\chi$. In particular, observables exhibited an unphysical divergence in the limit of massless $\chi$, associated to its longitudinal polarizations. Based on gauge symmetry, we show how to correct this issue. To this end, we consider two general models realizing the effective field theory description. Being the LFV generated either at tree level or at one loop, these processes are well behaved for light $m_\chi$. We discuss the most salient phenomenological consequences and its relevance in the searches for this kind of decays.

Pablo Roig

SciPost Phys. Proc. 16, 005 (2025) · published 14 July 2025 | Toggle abstract · pdf

Semileptonic exclusive tau decays in the Standard Model are reviewed. As it is well-known, they are a privileged arena to learn about low-energy hadronization. They also allow for a number of clean new physics tests, which have attracted much attention recently, probing scales as high as a few TeV. In light of forthcoming Belle-II data, perspectives on this area are bright.