Publications

Order by: publication date number of citations

• Reconstructing hadronically decaying tau leptons with a jet foundation model

  Laurits Tani, Joosep Pata, Joschka Birk

  SciPost Phys. Core 8, 046 (2025) · published 4 July 2025 | Toggle abstract · pdf

  The limited availability and accuracy of simulated data has motivated the use of foundation models in high energy physics, with the idea to first train a task-agnostic model on large and potentially unlabeled datasets. This enables the subsequent fine-tuning of the learned representation for specific downstream tasks, potentially requiring much smaller datasets to achieve performance comparable to models trained from scratch on larger datasets. We study how OmniJet-$\alpha$, one of the proposed foundation models for particle jets, can be used on a new set of tasks, and on a new dataset, in order to reconstruct hadronically decaying $\tau$ leptons. We show that the pretraining can successfully be utilized for this multi-task problem, improving the resolution of momentum reconstruction by about $50\%$ when the pretrained weights are fine-tuned, compared to training the model from scratch. While much work remains ahead to develop generic foundation models for high-energy physics, this early result of generalizing an existing model to a new dataset and to previously unconsidered tasks highlights the importance of testing the approaches on a diverse set of datasets and tasks.

• Lepton flavour universality tests and lepton flavour violation searches at LHCb

  Sara Celani

  SciPost Phys. Proc. 16, 021 (2025) · published 15 July 2025 | Toggle abstract · pdf

  The Standard Model (SM) of particle physics represents our most fundamental knowledge of elementary particles and their interactions. One of the cardinal properties of the SM which has been thoroughly studied during the past years is the so-called Lepton Flavour Universality (LFU): W and Z bosons are predicted to be equally coupled to the three lepton generations. Hints for deviations from LFU have been found by the LHCb collaboration in $b\to s\ell\ell$ and $b\to c\ell\nu$ decays, sparking great interest and further motivating the searches for lepton flavour violating processes. A general review of these results is presented, including prospects in view of the LHC and LHCb upgrade.

• Feasibility of tau g-2 measurements in ultra-peripheral collisions of heavy ions

  Nazar Burmasov, Evgeny Kryshen, Paul Buehler, Roman Lavicka

  SciPost Phys. Proc. 16, 022 (2025) · published 15 July 2025 | Toggle abstract · pdf

  The anomalous magnetic moment of the tau lepton, $a_\tau=(g_\tau - 2)/2$, is a sensitive probe of new physics but is extremely difficult to measure precisely in contrast to electron and muon moments. The best experimental limits were set by the DELPHI collaboration more than 15 years ago in studies of the ditau production in the $ee\to ee\tau\tau$ process. Ultra-peripheral collisions (UPCs) of heavy ions at the LHC may provide a unique opportunity to improve the $a_\tau$ constraints in the studies of ${\rm Pb + Pb}\to {\rm Pb + Pb}+\tau\tau$ process. We review recent proposals to study ditau production via semi-leptonic tau decays in Pb-Pb UPC with the available ATLAS and CMS data and discuss the feasibility to explore this process down to low transverse momenta of decay leptons with the ALICE and LHCb experiments.

• The Scattering and Neutrino Detector at the LHC

  Francesco-Luigi Navarria

  SciPost Phys. Proc. 16, 027 (2025) · published 15 July 2025 | Toggle abstract · pdf

  SND@LHC is a compact experiment that will detect high energy neutrinos produced by heavy flavour quarks at the LHC in the pseudo-rapidity region 7.2 $< \eta <$ 8.6. It is an hybrid system, comprising nuclear emulsions and electronic detectors, that allows all three $\nu$ flavours to be distinguished, thus opening an unique opportunity to probe the physics of charm production in the very forward region. The first phase aims at operating the detector throughout LHC Run 3 collecting a total of 150 fb$^{-1}$. The electronic subdetectors were assembled in the summer and recently operated in test beams.

• Measuring three-flavor neutrinos with FASER$\nu$ at the LHC

  Tomoko Ariga

  SciPost Phys. Proc. 16, 028 (2025) · published 15 July 2025 | Toggle abstract · pdf

  FASER$\nu$ at the Large Hadron Collider (LHC) is designed to directly detect neutrinos from a collider for the first time and study their cross sections at TeV energies. To date, no such measurements have been made. In 2018, a pilot detector was installed and collected proton-proton collision data of 12.2 fb$^{-1}$ at a center-of-mass energy of 13 TeV. We observed the first neutrino interaction candidates at the LHC, opening a new avenue for studying neutrinos from current and future high-energy colliders. During Run 3 of the LHC from 2022, we will deploy a neutrino detector with a target mass of 1.1 tons. We expect to collect $\sim$2,000 $\nu_e$, 6,000 $\nu_{\mu}$, and 40 $\nu_{\tau}$ interactions in the detector.

• Search for upward-going air showers with the fluorescence detector of the Pierre Auger Observatory

  Emanuele De Vito

  SciPost Phys. Proc. 16, 029 (2025) · published 15 July 2025 | Toggle abstract · pdf

  The fluorescence detector (FD) of the Pierre Auger Observatory is sensitive to upward-going air showers for energies above $10^{17}$ eV. Given its operation time and wide field of view, the FD has the potential to support or constrain the recent "anomalous" observations by the ANITA detector, interpreted as upward-going air showers of unexplained nature. We have used 14 years of data collected by the FD to search for upward-going showers using a set of quality selection criteria defined using 10% of the full data sample. To distinguish candidates from false positives, calculate the exposure and obtain the expected background, dedicated simulations for signal (upward-going events) and background (downward-going events) have been performed. Results of the analysis after unblinding the data set are presented. Finally, the exposure and sensitivity for the specific scenario of a signal being ascribed to tau lepton decay are calculated and the corresponding upper limits are shown as a function of primary energy and in different zenith angle ranges.

• Status of Radio MonteCarLow and Strong2020 $e^+e^-$ database activities

  Graziano Venanzoni

  SciPost Phys. Proc. 16, 033 (2025) · published 15 July 2025 | Toggle abstract · pdf

  During the last 15 years the Radio MonteCarLow Working Group has been providing valuable support to the development of radiative corrections and Monte Carlo generators for low energy $e^+e^-$ data and $\tau$-lepton decays. While the working group has been operating for more than 15 years without a formal basis for funding, parts of our program have recently been included as a Joint Research Initiative in the group application of the European hadron physics community, STRONG2020, to the European Union, with a more specific goal of creating an annotated database for low-energy hadronic cross sections in $e^+e^-$ collisions. We will report on both these initiatives.

• Status of the MUonE experiment

  Riccardo N. Pilato

  SciPost Phys. Proc. 16, 034 (2025) · published 15 July 2025 | Toggle abstract · pdf

  The latest measurement of the muon g-2, recently announced at Fermilab, exhibits a 4.2$\sigma$ discrepancy from the Standard Model prediction. The hadronic contribution $a_{\mu}^{HLO}$ represents the main source of uncertainty on the theoretical prediction. The MUonE experiment proposes a novel approach to determine $a_{\mu}^{HLO}$ by measuring the effective electromagnetic coupling in the space-like region, via $\mu - e$ elastic scattering. The measurement is performed by scattering a 160 GeV muon beam, available at CERN, on atomic electrons of a low-Z target. A Test run on a reduced detector is planned in 2022, to validate this proposal. The status of the experiment in view of the Test run is presented.

• Tau lepton averages by the HFLAV group

  Alberto Lusiani

  SciPost Phys. Proc. 17, 001 (2025) · published 23 July 2025 | Toggle abstract · pdf

  We document some features of the preliminary draft of the tau lepton averages for the incoming HFLAV report. We include the tau mass and lifetime averages, and a fit of measurements of tau branching fraction measurements. Elaborations of these results provide lepton universality tests and determination of $|V_{us}|$ with tau measurements.

• Electric and magnetic tau dipole moments revisited

  G. A. González-Sprinberg

  SciPost Phys. Proc. 17, 004 (2025) · published 23 July 2025 | Toggle abstract · pdf

  Precise measurements of magnetic and electric dipole moments are important tests of the Standard Model and beyond Standard Model physics, particularly for the electron and the muon. However, the situation presents distinctive challenges when dealing with the tau lepton due to its very short lifetime and relatively high mass. Here, we review the theoretical predictions and experimental measurements of both the anomalous magnetic and electric dipole moments of the tau lepton.