Publications

Order by: publication date number of citations

• Reconciling the FOPT and CIPT predictions for the hadronic tau decay rate

  Miguel A. Benitez-Rathgeb, Diogo Boito, Andre H. Hoang, Matthias Jamin

  SciPost Phys. Proc. 16, 007 (2025) · published 14 July 2025 | Toggle abstract · pdf

  In a recent work it was suggested that the discrepancy observed in the perturbation series behavior of the $\tau$ hadronic decay rate determined in the FOPT and CIPT approaches can be explained from a different infrared sensitivity inherent to both methods, assuming that the major source of the discrepancy is the asymptotic behavior of the series related to the gluon condensate renormalon. This implies that the predictions of both methods may be reconciled in infrared subtracted perturbation theory. In this talk we explore this implication concretely in the large-$\beta_0$ approximation, where the perturbation series is known to all orders, using a renormalon-free scheme for the gluon condensate.

  1 citation

• On the use of the operator product expansion in finite-energy sum rules for light-quark correlators

  Diogo Boito, Maarten Golterman, Kim Maltman, Santiago Peris

  SciPost Phys. Proc. 16, 006 (2025) · published 14 July 2025 | Toggle abstract · pdf

  Tau-based finite-energy sum-rule (FESR) analyses often assume that scales $s_0\sim m_\tau^2$ are large enough that (i) integrated duality violations (DVs) can be neglected, and (ii) contributions from non-perturbative OPE condensates of dimension $D$ scale as $(\Lambda_{QCD}/m_\tau )^D$, allowing the OPE series to be truncated at low dimension. The latter assumption is not necessarily valid since the OPE series is not convergent, while the former is open to question given experimental results for the electromagnetic, $I=1$ vector ($V$), $I=1$ axial vector ($A$) and $I=1$ $V+A$ current spectral functions, which show DV oscillations with amplitudes comparable in size to the corresponding $\alpha_s$-dependent perturbative contributions at $s\sim2-3$ GeV$^2$. Here, we discuss recently introduced new tools for assessing the numerical relevance of omitted higher-$D$ OPE contributions. Applying these to the "truncated OPE" strategy used in Refs. [M. Davier et al., Eur. Phys. J. C 74, 2803 (2014); A. Pich and A. Rodríguez-Sánchez, Phys. Rev. D 94, 034027 (2016)] and earlier work by the same authors, we find that this strategy fails to yield reliable results for the strong coupling from hadronic $\tau$ decays.

• Exclusive hadronic $\tau$ decays, within & beyond the Standard Model

  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.

• Strong coupling at the $\tau$-mass scale from an improved vector isovector spectral function

  Diogo Boito, Maarten Golterman, Kim Maltman, Santiago Peris, Marcus V. Rodrigues, Wilder Schaaf

  SciPost Phys. Proc. 16, 004 (2025) · published 14 July 2025 | Toggle abstract · pdf

  We perform a precise extraction of the QCD coupling at the $\tau$-mass scale, $\alpha_s(m_\tau)$, from a new vector isovector spectral function which combines ALEPH and OPAL distributions for the dominant channels, $\tau\to\pi \pi^0\nu_\tau$, $\tau\to 3\pi \pi^0\nu_\tau$ and $\tau\to \pi 3\pi^0\nu_\tau$, with estimates of sub-leading contributions obtained from electroproduction cross-sections using CVC, as well as BaBar results for $\tau \to K^-K^0\nu_\tau$. The fully inclusive spectral function thus obtained is entirely based on experimental data, without Monte Carlo input. From this new data set, we obtain $\alpha_s(m_\tau)=0.3077±0.0075$, which corresponds to $\alpha_s(m_Z)=0.1171±0.0010$. This analysis can be improved on the experimental side with new measurements of the dominant $\pi\pi^0$, $\pi 3\pi^0$, and $3\pi \pi^0$ $\tau$ decay modes.

• Monte Carlo Event Generator updates, for tau pair events at Belle II energies

  Sw. Banerjee, D. Biswas, T. Przedzinski, Z. Was

  SciPost Phys. Proc. 16, 003 (2025) · published 14 July 2025 | Toggle abstract · pdf

  The Monte Carlo for lepton pair production and $\tau$ decays consist of KKMC for lepton pair production, tauola for $\tau$ lepton decays and photos for radiative corrections in decays. An effort for adaptation of the system for precision data to be collected at Belle II experiment lead to extension of phase space generation modules both in photos and tauola to enable decays and/or radiative corrections of additional light lepton pairs. The phase-space and matrix element parts of the programs are separated, that is why extension to processes where lepton pair is produced through narrow resonances, like dark photon, was straight forward. In the present version of tauola, the list of $\tau$ decay channels is enriched with multitude of exotic ones, useful for searches of new physics. The hadronic currents parametrization of main decay channels is prepared for basic simulation in the experiment. The basis for future work on precise fits of hadronic currents including Machine Learning is retained, but development of necessary software solutions is left for the forthcoming years. Presented programs versions are available in stand-alone format from GitLab or through the basf2 system of Belle II software. Official distribution web pages, documenting programs tests, are retained but not necessarily up to date.

• Updated determinations of |V$_{us}$| with tau decays using new recent estimates of radiative corrections for light-meson leptonic decay rates

  Alberto Lusiani

  SciPost Phys. Proc. 16, 002 (2025) · published 14 July 2025 | Toggle abstract · pdf

  We update the |V$_{us}$| determinations using the HFLAV 2018 report tau branching fraction results with recent new estimates of the $\pi\ell2$ and $K\ell2$ radiative corrections. There are minor changes of the central values and uncertainties.

• Workshop on Tau Lepton Physics: $\mathbf{30^{th}}$ Anniversary

  Antonio Pich

  SciPost Phys. Proc. 16, 001 (2025) · published 14 July 2025 | Toggle abstract · pdf

  The first Workshop on Tau Lepton Physics took place at Orsay in 1990. The evolution of the field and some physics highlights are briefly described, following the presentations discussed at the fifteen $\tau$ workshops that have been held since then.

• Fidelity decay and error accumulation in random quantum circuits

  Nadir Samos Sáenz de Buruaga, Rafał Bistroń, Marcin Rudziński, Rodrigo M. C. Pereira, Karol Życzkowski, Pedro Ribeiro

  SciPost Phys. 19, 013 (2025) · published 8 July 2025 | Toggle abstract · pdf

  Fidelity decay captures the inevitable state degradation in any practical implementation of a quantum process. We devise bounds for the decay of fidelity for a generic evolution given by a random quantum circuit model that encompasses errors arising from the implementation of two-qubit gates and qubit permutations. We show that fidelity decays exponentially with both circuit depth and the number of qubits raised to an architecture-dependent power and we determine the decay rates as a function of the amplitude of the aforementioned errors. Furthermore, we demonstrate the utility of our results in benchmarking quantum processors using the quantum volume figure of merit and provide insights into strategies for improving processor performance. These findings pave the way for understanding how states evolving under generic quantum dynamics degrade due to the accumulation of different kinds of perturbations.

  2 citations

• Collective dynamics of densely confined active polar disks with self- and mutual alignment

  Weizhen Tang, Yating Zheng, Amir Shee, Guozheng Lin, Zhangang Han, Pawel Romanczuk, Cristián Huepe

  SciPost Phys. 19, 012 (2025) · published 8 July 2025 | Toggle abstract · pdf

  We study the emerging collective states in a simple mechanical model of a dense group of self-propelled polar disks with off-centered rotation, confined within a circular arena. Each disk presents self-alignment towards the sum of contact forces acting on it, resulting from disk-substrate interactions, while also displaying mutual alignment with neighbors due to having its center of rotation located a distance $R$ behind its centroid, so that central contact forces can also introduce torques. The effect of both alignment mechanisms produces a variety of collective states that combine high-frequency localized circular oscillations with low-frequency milling around the center of the arena, in fluid or solid regimes. We consider cases with small/large $R$ values, isotropic/anisotropic disk-substrate damping, smooth/rough arena boundaries, different densities, and multiple systems sizes, showing that the emergent collective states that we identify are robust, generic, and potentially observable in real-world natural or artificial systems.

• Generating long-distance magnetic couplings with flat bands

  Georges Bouzerar, Maxime Thumin

  SciPost Phys. 19, 011 (2025) · published 8 July 2025 | Toggle abstract · pdf

  One of the great challenges for the large-scale development of quantum technologies is to generate and control the entanglement of quantum bits through interactions of sufficiently long range. Two decades ago, spin chains have been proposed for quantum communication. Unfortunately, couplings are of very short range in general which drastically limits the communication to very short distances. Here, we demonstrate that the presence of flat bands (FBs) can trigger very long-distance magnetic couplings in spin chains. Furthermore, we show that the typical decaying lengthscale is directly related to the quantum metric of the flat band eigenstates. We have validated the robustness of our results in the case where flat bands become weakly dispersive. We believe that our unexpected findings could open up an alternative route to enable long-distance quantum communication.

  1 citation