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Search for dark matter axions at 1-2 eV with a RADES-DarkQuantum prototype haloscope at CERN North Area
No full textThe axion remains one of the most compelling candidates for dark matter, with strong theoretical motivation from the Peccei–Quinn solution to the strong-CP problem. Despite a surge of global efforts, the QCD axion band is still only sparsely explored, particularly in the low-mass range around –, which is currently completely untested. The RADES “low-frequency” program directly addresses this gap. Supported by the ERC Synergy Grant \textit{DarkQuantum}, it aims to combine innovative cavity designs, cryogenics, and quantum-limited readout technologies to deliver a decisive search for axion dark matter. As part of this effort, the collaboration is constructing the DQLF prototype, a one-meter cavity system with dilution refrigeration and SQUID-based readout, currently under construction. While conceived as a technical prototype for future longer cavities to be operated in the BabyIAXO superconducting magnet, its scale and capabilities already allow for very relevant physics data. Installing the prototype inside a CERN North Area dipole magnet—most favorably the M1 magnet during LS3—would enable the first exploration of the – mass range, with sensitivity reaching well into the QCD axion band. Even under conservative assumptions for the factor and noise temperature, the setup would probe benchmark models such as KSVZ and DSFZ; in the most optimistic case it could fully exclude (or discover) QCD axions under the axion dark matter paradigm in this range. The collaboration is well resourced: DarkQuantum funds cover cavity construction, cryogenic systems, and readout electronics, while manpower for data taking and analysis is already in place in the collaboration (and has already organized data taking runs at CERN in the past). Additional PBC support is contributing to cavity design. The only elements required from CERN are access to the M1 magnet and associated technical expertise, along with coverage of magnet operation costs during the approved run periods. With LS3 providing a unique and timely window, this proposal offers CERN the opportunity to host a world-leading dark matter axion search, yielding high-impact results even in modest scenarios and potentially delivering a definitive test of the axion dark matter paradigm in the unexplored – mass range
ATLAS and CMS HH Non-Resonant Searches in the 2b2l/2b2V Final States
No full textSlides for HiggsPairs202
Measurement of the azimuthal anisotropy of charged particles in TeV OO and NeNe collisions with the ATLAS detector
No full textThis paper presents the first measurements of the azimuthal anisotropy coefficients , which quantify the -order Fourier modulation of charged-particle azimuthal distributions, for -4 in TeV and collisions recorded with the ATLAS detector at the Large Hadron Collider in 2025. The coefficients are measured as a function of transverse momentum (), collision centrality, and event multiplicity. They are extracted using two complementary methods: two-particle correlations with a template-fit subtraction of short-range non-flow contributions, and four-particle subevent cumulants, which intrinsically suppress non-flow effects and provide sensitivity to flow fluctuations. The results show a clear hierarchy and a non-monotonic dependence on , reaching a maximum around 2 GeV, consistent with trends observed in heavy-ion collisions. Detailed comparisons between the two collision systems reveal an enhanced in central collisions, consistent with theory expectations based on the predicted prolate deformation of neon nuclei, in contrast to the slightly tetrahedral structure predicted for oxygen. The four-particle cumulant results highlight strong event-by-event fluctuations and provide the greatest sensitivity to nuclear shape effects. These measurements can place new constraints on the initial geometry and the hydrodynamic response in light-ion collisions, offering valuable input for models of nuclear structure.This paper presents the first measurements of the azimuthal anisotropy coefficients , which quantify the -order Fourier modulation of charged-particle azimuthal distributions, for -4 in TeV and collisions recorded with the ATLAS detector at the Large Hadron Collider in 2025. The coefficients are measured as a function of transverse momentum (), collision centrality, and event multiplicity. They are extracted using two complementary methods: two-particle correlations with a template-fit subtraction of short-range non-flow contributions, and four-particle subevent cumulants, which intrinsically suppress non-flow effects and provide sensitivity to flow fluctuations. The results show a clear hierarchy and a non-monotonic dependence on , reaching a maximum around 2 GeV, consistent with trends observed in heavy-ion collisions. Detailed comparisons between the two collision systems reveal an enhanced in central collisions, consistent with theory expectations based on the predicted prolate deformation of neon nuclei, in contrast to the slightly tetrahedral structure predicted for oxygen. The four-particle cumulant results highlight strong event-by-event fluctuations and provide the greatest sensitivity to nuclear shape effects. These measurements can place new constraints on the initial geometry and the hydrodynamic response in light-ion collisions, offering valuable input for models of nuclear structure
Measurement of the charged particle nuclear modification factor in oxygen-oxygen collisions with CMS
No full textA hot medium, known as the quark-gluon plasma (QGP), is created in collisions of relativistic heavy nuclei such as lead or gold. Highly energetic quarks and gluons, collectively referred to as partons, lose energy as they travel through the QGP leading to suppressed production of particles with transverse momenta () of roughly 10--100 GeV. This suppression is typically quantified with the nuclear modification factor (). Questions regarding what minimum system size is required to see parton energy loss effects remain, as no such suppression has been seen in smaller proton-lead collisions. Experiments involving light nuclei examine a domain that lies between these two extreme cases. Using of oxygen-oxygen (OO) collisions and of proton-proton data collected at a nucleon-nucleon center-of-mass energy of TeV by the CMS experiment at the CERN LHC, charged particle invariant cross sections and the OO charged particle are measured as a function of particle for the first time. The is notably suppressed, with a local minimum of at GeV, but increases to a value of at GeV. To evaluate if parton energy loss effects may be present in OO collisions, the data are compared to previous measurements of other collision systems and a variety of theoretical models
Measurement of rare electroweak processes including vector boson scattering and triboson in ATLAS
No full textMeasurement of rare processes in the electroweak sector poses unprecedented stringent test of the SM theory, and in particular offers unique sensitivity to study the electroweak symmetry breaking (VBS processes) and the quartic boson self-couplings (VBS and triboson processes). In addition to cross-section measurements, systematic study of boson polarization states in VBS processes is being actively pursued to hopefully bring further sensitivity and uncover deeper insights. This talk will summarize recent achievements from ATLAS on this topic
High Throughput FPGA Deployment of Distilled Deep Sets Networks for Jet Preselection in the High Level Trigger
No full textDeep Sets-based neural networks are well-suited to learning from unordered, variable-length inputs such as particle tracks associated with jets. Their permutation-invariant structure makes them attractive for high-energy physics (HEP) applications where input ordering is ambiguous and throughput is a critical constraint. In this work, we explore the use of such architectures on Field-Programmable Gate Arrays (FPGAs) to enable fast and resource-efficient inference within the High-Level Trigger (HLT), where track-level features become available and event processing must be optimized for rate rather than latency. We build on the DIPS (Deep Impact Parameter Sets) algorithm, a Deep Sets-based flavour-tagging model previously used in ATLAS, and adapt it for quantization-aware training and efficient FPGA implementation using QKeras and hls4ml. To maximize throughput without sacrificing classification performance, we introduce knowledge distillation: a high-capacity teacher network guides the training of a compact student model optimized for FPGA deployment. This approach allows us to retain strong discriminative power while drastically reducing inference cost. Our implementation demonstrates that Deep Sets networks can be effectively mapped to FPGA hardware, including mechanisms for handling variable-length, permutation-invariant inputs. We report detailed results from real FPGA deployments, including resource usage, measured latency, and especially sustained throughput under different configurations. Rather than competing directly with more sophisticated architectures such as graph neural networks (GNNs), our goal is to provide a high-throughput preselection stage that can reduce the number of events requiring costly downstream inference. In doing so, we enable a more efficient use of compute resources in the HLT pipeline, providing early rejection capabilities with minimal impact on tagging performance. This work highlights a complementary strategy for deploying ML on FPGAs in HEP: prioritizing throughput to enable scalable inference pipelines and alleviate computational bottlenecks, especially in data-rich environments such as the upgraded ATLAS trigger
Study of identified particle production in high multiplicity pp collisions at s=13 TeV with ALICE at the LHC
No full textHigh-multiplicity proton–proton and proton-lead collisions at the LHC exhibit signatures similar to those observed in lead-lead collisions, such as mass-dependent hardening of transverse momentum spectra and strangeness enhancement. In heavy-ion collisions, these features are attributed to the formation of a deconfined state of matter composed of quarks and gluons, known as the Quark–Gluon Plasma (QGP). However, their origin in small systems has yet to be understood. This contribution presents π±, K±, and, p(p̄) measurements in high-multiplicity pp collisions at s=13 TeV at midrapidity (|y|< 0.5), reaching unprecedented charged-particle multiplicities, about five times higher than the average in pp collisions. The results are compared as a function of charged-particle multiplicity to measurements in pp, pA, and AA collisions. The particle-production mechanisms affecting dynamics and hadrochemistry are tested by measuring the average transverse momentum and integrated particle yields. The results are also compared to predictions from the state-of-the-art Monte Carlo Model, PYTHIA8
Recent Higgs (and HH) measurements at LHC
No full textFrom its discovery to the present day, Higgs boson research within the ATLAS and CMS experiments remains at the forefront of CERN's scientific program. This particle still hides many mysteries that require thorough exploration. This presentation showcases the most recent results obtained by the ATLAS and CMS collaborations in Higgs physics, utilizing data collected during the Run 2 and Run 3 phases of the LHC
Module assembly and testing for the HGTD ATLAS upgrade
No full textThe High Granularity timing detector (HGTD) is one of the ATLAS upgrades and is designed to provide a per-track timing information of 50 ps over the full detector lifetime. This information will contribute to pileup mitigation in the operations of the ATLAS detector at the High-Luminosity LHC. HGTD deploys low gain avalanche silicon detectors (LGADs) with a segmentation into a 15x15 matrix with 1.3x1.3 mm2 pads. Sensors are bump-bonded to the ALTIROC readout ASIC, and two of such hybrids are attached to a single PCB to constitute an HGTD module. The HGTD will be instrumented with more than 8000 modules. This talk will discuss the requirements and the methods used for the assembly of modules and the procedures deployed to verify their quality and test their functionality. The results achieved on the module performance will be presented