Publications

Order by: publication date number of citations

• Status and prospects for $\tau$ property measurements at Belle II

  Michel Hernández Villanueva

  SciPost Phys. Proc. 16, 015 (2025) · published 14 July 2025 | Toggle abstract · pdf

  Belle II is a major upgrade of the Belle detector, operating at the SuperKEKB asymmetric-energy $e^+e^-$ collider with a design luminosity of 8×$10^{35}$ cm$^{-2}$s$^{-1}$. To date, the detector has recorded over 200 fb$^{-1}$ of data and aims to collect 50 ab$^{-1}$, a factor of 50 more than its predecessor. Belle II has a broad $\tau$ physics program, from high-precision measurements of Standard Model parameters to searches of new non-Standard-Model interactions. In this work, we review the status of the Belle II experiment and the prospects for the measurement of the $\tau$ lepton mass and lifetime, which are fundamental inputs in tests of LFU violation.

• Probing lepton flavor violation via $e\tau$ production in an effective framework at a future electron-positron circular coll

  Seyed Mohsen Etesami, Reza Jafari, Mojtaba Mohammadi Najafabadi, Seddigheh Tizchang

  SciPost Phys. Proc. 16, 016 (2025) · published 14 July 2025 | Toggle abstract · pdf

  In the Standard Model framework, lepton flavor is conserved in interactions. However, it can be violated in certain scenarios beyond the Standard Model. In this study, we consider $(e^{±}\tau^{\mp})$ production through a four-Fermi lepton flavor violation interaction at the future electron-positron circular collider (FCC-ee). To constrain the Wilson coefficients at four center-of-mass energies $157.5, 162.5, 240$, and $365$ GeV that have been proposed for the FCC-ee, a Standard Model Effective Field Theory (SMEFT) is used. The main sources of background are accounted for, and the study incorporates realistic detector effects. To enhance the results, we combine the individual constraints obtained at each center-of-mass energy. We show that the combined limits improve the sensitivity to lepton flavor violation couplings by a factor of approximately three compared to the individual results and are competitive with the Belle II prospects.

• Multiscale response of ionic systems to a spatially varying electric field

  Jesper Schmidt Hansen

  SciPost Phys. 2, 017 (2017) · published 27 May 2017 | Toggle abstract · pdf

  In this paper the response of ionic systems subjected to a spatially varying electric field is studied. Following the Nernst-Planck equation, two forces driving the mass flux are present, namely, the concentration gradient and the electric potential gradient. The mass flux due to the concentration gradient is modelled through Fick's law, and a new constitutive relation for the mass flux due to the potential gradient is proposed. In the regime of low screening the response function due to the potential gradient is closely related to the ionic conductivity. In the large screening regime, on the other hand, the response function is governed by the charge-charge structure. Molecular dynamics simulations are conducted and the two wave vector dependent response functions are evaluated for models of a molten salt and an ionic liquid. In the low screening regime the response functions show same wave vector dependency, indicating that it is the same underlying physical processes that govern the response. In the screening regime the wave vector dependency is very different and, thus, the overall response is determined by different processes. This is in agreement with the observed failure of the Nernst-Einstein relation.

• Stochastic resetting and large deviations

  Martin R. Evans, John C. Sunil

  SciPost Phys. Lect. Notes 103 (2025) · published 16 October 2025 | Toggle abstract · pdf

  Stochastic resetting has been a subject of considerable interest within statistical physics, both as means of improving completion times of complex processes such as searches and as a paradigm for generating nonequilibrium stationary states. In these lecture notes we give a self-contained introduction to the toy model of diffusion with stochastic resetting. We also discuss large deviation properties of additive functionals of the process such as the cost of resetting. Finally, we consider the generalisation from Poissonian resetting, where the resetting process occurs with a constant rate, to non-Poissonian resetting.

• Recent progress on two-loop massless pentabox integrals with one off-shell leg

  D. Canko, A. Kardos, C. G. Papadopoulos, A. V Smirnov, N. Syrrakos, C. Wever

  SciPost Phys. Proc. 7, 037 (2022) · published 21 June 2022 | Toggle abstract · pdf

  Analytic expressions in terms of polylogarithmic functions for all three families of planar two-loop five-point Master Integrals with one off-shell leg are presented. The Simplified Differential Equations approach is the only known way to fulfil this task due to its unique factorisation property of the symbols of the canonical differential equation. The results are relevant to the study of many $2\to 3$ scattering processes of interest at the LHC.

• Functional renormalization group approach for signal detection

  Vincent Lahoche, Dine Ousmane Samary, Mohamed Tamaazousti

  SciPost Phys. Core 7, 077 (2024) · published 2 December 2024 | Toggle abstract · pdf

  This review paper utilizes renormalization group techniques for signal detection in nearly continuous positive spectra. We emphasize the universal aspects of the analogue field-theory approach. The primary objective is to present an extended self-consistent construction of the analogue effective field-theory framework for data, which can be interpreted as a maximum entropy model. In particular, we leverage universality arguments to justify the $\mathbb{Z}_2$ symmetry of the classical action, highlighting the existence of both a large-scale (local) regime and a small-scale (nonlocal) regime. Secondly, in relation to noise models, we observe the universal relationship between phase transitions and symmetry breaking near the detection threshold. Finally, we address the challenge of defining the covariance matrix for tensor-like data. Based on the cutting graph prescription, we note the superiority of definitions that rely on complete graphs of large size for data analysis.

• The importance of multiple scatterings in medium-induced gluon radiation

  Carlota Andres, Fabio Dominguez, Marcos Gonzalez Martinez

  SciPost Phys. Proc. 10, 016 (2022) · published 10 August 2022 | Toggle abstract · pdf

  In this work we disentangle the underlying physical picture of the in-medium gluon radiation process across its different energy regimes by comparing the recently obtained fully-resummed -- without any further approximations -- BDMPS-Z in-medium emission spectrum with the extensively used analytical approaches. We observe that in the high-energy regime the radiation process is dominated by a single hard scattering, while in the intermediate-energy region coherence effects among multiple scatterings are crucial. Finally, we prove that in the low-energy regime the dynamics is again controlled by a single scattering but where one must include a suppression factor accounting for the probability of not having any further scatterings.

• Non-adiabatic linear response in open quantum systems

  Xiaotian Nie, Wei Zheng

  SciPost Phys. 19, 161 (2025) · published 19 December 2025 | Toggle abstract · pdf

  Adiabatic theorem and non-adiabatic corrections have been widely applied in modern quantum technology. Recently, non-adiabatic linear response theory has been developed to probe the many-body correlations in closed systems. In this work, we generalize the non-adiabatic linear response theory to open quantum many-body systems. We show that, similar to the closed case, the first-order deviation from the instantaneous steady state is memoryless—it depends only on the final parameters and not on the initial state or ramping path. When ramping the Hamiltonian, the linear response of observables is governed by the derivative of the retarded Green's function, as in closed systems. In contrast, ramping the dissipation gives rise to a different response, characterized by a high-order correlation function defined in the steady state. Our results offer a compact and physically transparent formulation of non-adiabatic response in open systems, and demonstrate that ramping dynamics can serve as a versatile tool for probing many-body correlations beyond equilibrium.

• Tau identification in CMS during LHC run 2

  Mohammad Hassan Hassanshahi

  SciPost Phys. Proc. 16, 018 (2025) · published 15 July 2025 | Toggle abstract · pdf

  The LHC Run 2 data-taking period was characterized by an increase in instantaneous luminosity and center-of-mass energy. Several techniques have been deployed in the CMS experiment to reconstruct and identify tau leptons in this environment. The DeepTau identification algorithm is used to identify hadronically decaying tau leptons from quark and gluon induced jets, electrons, and muons. Compared to previously used MVA identification algorithms, the use of deep-learning techniques brought a noticeable improvement in the tau identification and rejection of contaminating sources. Low transverse momentum topologies were addressed separately with a dedicated identification algorithm, while machine learning techniques were implemented to improve the identification of the tau hadronic decay channels. These algorithms have been already used for several published physics analyses in CMS. The algorithms are presented together with their measured performances.

• Exciton dissociation in organic solar cells: An embedded charge transfer state model

  Jouda Jemaa Khabthani, Khouloud Chika, Alexandre Perrin, Didier Mayou

  SciPost Phys. 18, 038 (2025) · published 31 January 2025 | Toggle abstract · pdf

  Organic solar cells are a promising avenue for renewable energy, and our study introduces a comprehensive model to investigate exciton dissociation processes at the donor-acceptor interface. Examining quantum efficiency and emitted phonons in the charge transfer state (CTS), we explore scenarios like variations of the environment beyond the CTS and repulsive/attractive potentials. The donor-acceptor interface significantly influences the injection process, with minimal impact from the environment beyond the CTS. Attractive potentials can create localized electron states at the interface, below the acceptor band, without necessarily hampering a good injection at higher energies. Exploring different recombination processes, including acceptor-side and donor-side recombination, presents distinct phases for the injection process versus the initial energy of the electron and the recombination rate. Our study highlights the important role of the type of recombination in determining the quantum efficiency and the existence of hot or cold charge transfer states. Finally, depending on the initial energy of the electron on the donor side, three distinct injection regimes are exhibited. The present model should be helpful for optimizing organic photovoltaic cell interfaces, highlighting the critical parameter interplay for enhanced performance.