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Mixture-of-Experts Graph Transformers for Interpretable Particle Collision Detection
No full textThe Large Hadron Collider at CERN produces immense volumes of complex data from high-energy particle collisions, demanding sophisticated analytical techniques for effective interpretation. Neural Networks, including Graph Neural Networks, have shown promise in tasks such as event classification and object identification by representing collisions as graphs. However, while Graph Neural Networks excel in predictive accuracy, their "black box" nature often limits their interpretability, making it difficult to trust their decision-making processes. In this paper, we propose a novel approach that combines a Graph Transformer model with Mixture-of-Expert layers to achieve high predictive performance while embedding interpretability into the architecture. By leveraging attention maps and expert specialization, the model offers insights into its internal decision-making, linking predictions to physics-informed features. We evaluate the model on simulated events from the ATLAS experiment, focusing on distinguishing rare Supersymmetric signal events from Standard Model background. Our results highlight that the model achieves competitive classification accuracy while providing interpretable outputs that align with known physics, demonstrating its potential as a robust and transparent tool for high-energy physics data analysis. This approach underscores the importance of explainability in machine learning methods applied to high energy physics, offering a path toward greater trust in AI-driven discoveries
Early Galaxies from Rare Inflationary Processes and JWST Observations
No full textRare Poisson processes (PP) during cosmic inflation can lead to signatures that are localized in position space and are not well captured by the standard two- or higher-point correlation functions of primordial density perturbations. As an example, PP can lead to localized overdense regions that are far denser than the ones produced through standard inflationary fluctuations. As a result, such overdense regions collapse earlier than expected based on the standard CDM model and would host anomalously high-redshift galaxies. We describe some general aspects of such PP and consider a particular realization in the context of inflationary particle production. We then show that the masses and redshifts of the resulting galaxies can lie in a range discoverable by the James Webb Space Telescope (JWST) and future surveys, while being consistent with existing constraints on the matter power spectrum and UV luminosity functions at lower redshifts
Magnetic and Mechanical Design of the Large Aperture HTS Superconducting Dipoles for the Accelerator Ring of the Muon Collider
No full textTo further explore the physics beyond the capabilities of the LHC and its High-Luminosity Upgrade (HL-LHC), particle physicists are studying advanced accelerators in order to perform finer measurements and/or reach higher energies. Upon the recommendation of the Updated European Strategy for Particle Physics (ESPP), an International Muon Collider Collaboration has been established to investigate the feasibility of a muon collider facility with a center-of-mass energy of 10 TeV. This endeavor is confronted with several technical challenges, primarily arising from the brief muon lifetime at rest, which is only 2.2 s. Addressing this stringent constraint necessitates the deployment of innovative technologies, including challengingmagnets, RF systems, targets, shielding, and cooling methodologies. This paper focuses on optimizing the electromagnetic and mechanical aspects of high-temperature superconducting (HTS) dipoles with large rectangular aperture for the accelerator ring, with a bore field up to 10 T, using finite element techniques. The objectives include ensuring a precise control over magnetic field uniformity and a preliminary evaluation of the mechanical behaviour of the HTS coils. The study is aligned with the priority set by ESPP on technological advancements, notably in high-field superconducting magnets, crucial components for any forthcoming circular collider
LHCb Computing Resources: 2026 requests
No full textThis document presents an estimate of the offline computing resources needed by LHCb in the 2026 WLCG year. The computing requests are based on the Computing Model Technical Design Report for the LHCb Upgrade, adjusted to the current values of its main parameters, to the currently known LHC running schedule, to the current usage of computing resources, and to the expected activities to be performed by the LHCb experiment
Higgs self-coupling at the FCC-hh
No full textThe Higgs self-coupling governs the shape of the Higgs potential and its precise determination is one of the main goals at future colliders. Here we present a new study based on fast simulations at the FCC-hh, assuming √ = 100 TeV and an integrated luminosity of 30 ab. The _ selfcouplingmodifier is determined from double Higgs production in two channels, the and the ℓℓ + T final states. The drives the precision, down to 3.6%, while the ℓℓ + Tachieves an uncertainty of 22%, however being a benchmark measurement for the impact of pileup. A further study on the resolution of the invariant mass of the two b-jets in shows that, with an optimal calorimeter and b-tagging algorithm achieving a resolution of 3% on , a precision ≤ 2% on _ can be reached
Azimuthal anisotropy from quantum interference in photoproduction in ultra-peripheral collisions with ALICE
No full textUltra-peripheral heavy-ion collisions (UPCs) occur when the impact parameter of the collision is greater than the sum of the radii of the colliding nuclei. UPCs allow one to study photon-induced reactions, such as the photoproduction of a vector meson, which is a well-established tool to probe the gluon structure of the colliding nuclei. We will focus on the measurement of the impact-parameter dependence of the azimuthal anisotropy in the meson photoproduction. The interference originates from the linear polarization of the exchanged virtual photons and from quantum interference between amplitudes contributing to the photoproduction process.We present the results of the first measurement of this kind at the LHC, using Pb--Pb UPCs and the ALICE detectors. The anisotropy is studied via the distribution of a variable, , that is, approximately, the angle between the transverse momentum of the and that of one of its two decay pions. Models predict a modulation of the yield. The amplitude of such a modulation was measured in three impact parameter ranges, defined by event classes with different neutron emission requirements. The amplitude of the modulation is found to increase by about one order of magnitude from large to small impact parameters, in agreement with the available theoretical predictions
La justice interne au CERN et sa réforme
No full text« La justice interne au CERN et sa réforme»
Séminaire organisé et présenté par l’Association du personnel
Sujet : Pourquoi un système de justice interne performant est indispensable pour les membres du personnel du CERN ainsi que pour l’Organisation?
Quels sont les mécanismes existants, les améliorations possibles, les motivations et le statut de la réforme en cours?
Intervenants : Sebastien Evrard, Nicolas Salomon
Langue : Francais, traduction en anglaise
‘’CERN's internal justice system and its reform‘’.
Seminar organised and presented by the Staff Association
Subject: Why an efficient internal justice system is essential for the members of the personnel of CERN, as well as for the Organization?
What are the existing mechanisms, possible improvements, motivations, and the status of the ongoing reform?
Speakers: Sebastien Evrard, Nicolas Salomon
Language: French, with English translation</p
Visit by Professor Karen O'Brien, Durham University, Vice-Chancellor, United Kingdom of Great Britain and Northern Ireland
No full textVisit by Professor Karen O'Brien, Vice-Chancellor, Durham University, United Kingdom of Great Britain and Northern Irelan
Quark and gluon momentum fractions in the pion and in the kaon
No full textWe present results on the momentum fraction carried by quarks and gluons in the pion and the kaon. We employ three gauge ensembles generated with Wilson twisted-mass clover-improved fermions with physical quark masses. We perform, for the first time, a continuum extrapolation directly at the physical pion. We find that the total momentum fraction carried by quarks is and and by gluons and in the pion and in the kaon, respectively, in the scheme and at the renormalization scale of 2 GeV.Having computed both the quark and gluon contributions in the continuum limit, we verify the momentum sum, finding 0.984(89) for the pion and 1.13(11) for the kaon.We present results on the momentum fraction carried by quarks and gluons in the pion and the kaon. We employ three gauge ensembles generated with Wilson twisted-mass clover-improved fermions with physical quark masses. We perform, for the first time, a continuum extrapolation directly at the physical pion. We find that the total momentum fraction carried by quarks is and and by gluons and in the pion and in the kaon, respectively, in the scheme and at the renormalization scale of 2 GeV. Having computed both the quark and gluon contributions in the continuum limit, we verify the momentum sum, finding 0.984(89) for the pion and 1.13(11) for the kaon
Streamlining ATLAS Monte Carlo Generator Validation with PAVER
No full textMonte Carlo simulations are crucial in modern high-energy physics, providing theoretical predictions that are used for experimental analyses. Hence, efficient and systematic validation of these simulations is critical to ensure the reliability and reproducibility of results. The PAVER system has been developed to meet this requirement by centralizing and automating the validation workflow, incorporating statistical tools and collaborative review processes to ensure high-quality Monte Carlo production. This paper discusses its workflow, features, and impact, emphasizing the contribution to efficient validation and resource optimization within the ATLAS experiment