The Dark Energy Spectroscopic Instrument (DESI) produced in 2024 the most precise measurement yet of the universe’s expansion, mapping galaxies and quasars in unparalleled detail. This marks the first time scientists have measured the expansion history from 8 to 11 billion years ago with a precision better than 1%, providing a powerful tool to study dark energy. IFAE researchers played a key role in one of the major studies, contributing to groundbreaking insights into the evolution of the cosmos.

In 2024, ICREA researcher Diego Blas launched GravNet alongside European collaborators, a pioneering project to search for high-frequency gravitational waves. Funded by an ERC Synergy Grant, GravNet aims to develop novel detectors that could open a new observational window into the early universe. Blas contributed key ideas to explore Gravitational Waves in the the MHz–GHz frequency range, potentially shedding light on dark matter and primordial cosmological events.

IFAE organized the LVK meeting in September 2024 (being M. Martínez the chair of the LOC) with the attendance of 400 persons coming to Barcelona and additional 400 attending the meeting online (https://lvkmeeting2024.ifae.es/)

During 2024, the LST collaboration has accomplished a big step forward towards having the four LSTs of the CTAO northern site at the RMO operational. The construction has moved from civil works to the actual construction of the structures and the installation of subsystems. The year finished with the three structures ready, two of them with the support for the cameras mounted and one of them with all the mirrors mounted. The rest of the mirrors and the cameras are ready to be installed.

The IFAE Neutrino group has successfully contributed to the upgrade of the ND280 near detector for the T2K-II phase and future use in the Hyper-Kamiokande (HK) experiment. The upgrade, completed in May 2024, involved the installation of three new subdetectors: the SuperFGD scintillator tracker, high-angle time projection chambers (HAT), and a time-of-flight (TOF) detector. IFAE played a key role, especially in the HATs and project coordination, with the IFAE PI serving as Co-Project Leader and Technical Coordinator. Neutrino beam data was collected in June and late 2024. The group is also active in the Water Cherenkov Test Experiment (WCTE) at CERN, supporting HK development.

Vector-like leptons (VLLs) emerge in various beyond-the-Standard-Model scenarios, including Composite Higgs models, extra-dimensional theories, and grand unified theories. At the Large Hadron Collider (LHC), VLLs are produced in pairs via the electroweak interaction, resulting in significantly lower production cross-sections compared to their colored counterparts, vector-like quarks, which are produced via the strong interaction. Consequently, searches for VLLs at the LHC have been relatively scarce. Using the full Run 2 dataset collected with the ATLAS detector, the IFAE group has conducted two pioneering searches for VLLs, achieving unprecedented sensitivity to their production. One search targets pairs of vector-like electrons or muons, each decaying into an electron or muon accompanied by a W, Z, or Higgs boson. The second search focuses on a special class of VLLs predicted by the so-called 4321 Model, which aims to explain the observed “flavor anomalies.” In this case, VLL pairs decay through intricate cascades involving third-generation fermions, such as tau leptons, top quarks, and b-quarks. Both searches are designed to detect striking final-state signatures using sophisticated analysis techniques. While no significant excess was observed, the results set the world’s most stringent direct limits on VLL masses, reaching the TeV scale for the first time. The search will continue with higher-statistics data from Run 3 of the LHC, extending sensitivity to even heavier masses and exploring uncharted territory in the quest for new physics.

In this work, the IFAE group demonstrated the existence of a new type of superconducting material, nitridized aluminum, or NitrAl. This material was produced to build new types of quantum circuits with better properties than those offered by bare aluminum, which is the standard material used to make superconducting qubits. The work was also the first fully experimental paper published by the QCT group at IFAE with the samples produced at CNM and the data acquired at IFAE. This was part of a collaboration between IFAE and CNM, in particular with Dr. G. Rius.

In 2024, researcher Fabrizio Rompineve received the Buchalter Cosmology Prize (Third Prize) for a study exploring gravitational wave signals from the QCD phase transition in the early universe. The awarded work proposed a novel way to test cosmological models using pulsar timing arrays, offering a potential window into physics beyond the Standard Model. Rompineve’s contribution highlights the growing role of gravitational waves as probes of the universe’s earliest moments.

In 2024, the IFAE Gamma-ray group conducted an extensive optimization, calibration, and configuration campaign for the silicon photomultipliers and readout ASIC of the HERD Fiber Tracker (FIT) and Plastic Scintillator Detector (PSD) at the IFAE laboratories. This effort enabled a comprehensive characterization of these components, assessing key parameters such as noise levels, calibration factors, thresholds, dynamic range, linearity, and response time. The resulting optimized electronic system was used to instrument a prototype of the FIT, which was successfully tested in a high-energy ion beam campaign at the CERN SPS accelerator in November 2024. The acquired data validated the FIT’s spatial resolution and charge identification capabilities, achieving a key project milestone. Additionally, these results open the possibility of adapting the fiber tracker concept for other astroparticle physics space missions.

In 2024, the IFAE analysis activity related to the test of General Relativity focused on the study of environmental effects and how these affect signals from compact binary mergers, a crucial aspect overlooked in previous LVK analyses. A dedicated analysis was performed on O2 and O3 events. It shows no concrete evidence that supports the presence of astrophysical environments, and upper bounds on the associated astrophysical densities were established. Most importantly, it demonstrates that environmental effects can significantly bias parameter recovery in the vacuum model, even when undetectable. Furthermore, projections suggest that ET and B-DECIGO have the potential to explore the impacts of accretion disks and superradiant boson clouds on compact binaries. Once again, this is an example of collaborative effort between IFAE theory and GW groups.The results were published in G. Caneva et al.,Phys. Rev. Lett. 132, 251401 (2024).

During the past year, the liner triplet pre-production was completed. The module assembly and extensive testing were carried out in the IFAE clean rooms. Due to delays in the ITk Pixel schedule, the modules included the ITkPixV1.1 chip instead of the final V2.0 front-end. However, the pre-production was otherwise expected to be similar to the final production. The evaluation of the modules included stress tests (thermal cycles) and charge collection tests using external radioactive sources.

Ten modules—two more than required—were shipped to SLAC for loading, and the Production Readiness Review (PRR) was successfully completed in November 2024. As of now, the first ITkPixV2.0 digital triplet has been successfully tested at IFAE, and production is expected to begin in the spring of 2025.

Among the novelties of the CTAO, there will be its operation as an observatory open to the astronomical community, a requirement that prompted gamma-ray astronomers to develop standardised data formats and open-source analysis tools. This new open pipeline constitutes an excellent instrument to disseminate the two decades of observations already gathered by current-generation gamma-ray instruments, so far of proprietary access. IFAE and PIC are leading the implementation of the MAGIC “Data Legacy”, a public archive of all MAGIC stereoscopic observations. The first milestone of this project was achieved this year with the validation of the analysis of 160 hours of standardised MAGIC observations with the aforementioned open pipeline, demonstrating the readiness of the software tools necessary to realise the legacy. To advertise the legacy effort and attract the interest of the community, 60 h of MAGIC data were also, for the first time, released to the public for scientific exploitation.

Thanks to its expertise in software development and data analysis and management, the group joined the EU-funded Astrophysical Centre for Multimessenger studies in Europe (ACME) initiative, within the scope of which it will keep developing the tools for the MAGIC data legacy, organise training events on gamma-ray data analysis, and facilitate virtual and trans-national access to the MAGIC data.

The Physics of the Accelerating Universe Survey (PAUS) released in 2024 a groundbreaking cosmic distance catalogue, collecting data on 1.8 million astronomical objects observed over 200 nights between 2015 and 2019 using the PAUCam on the William Herschel Telescope in La Palma. This dataset will help astronomers map the formation of cosmic structures influenced by dark matter and dark energy with unprecedented precision. The PAUCam camera was designed and integrated in Barcelona by IFAE in collaboration with ICE-CSIC, PIC, IEEC, CIEMAT, and IFT-UAM/CSIC.

The QCT group at IFAE joined the RADES (Relic Axion DEtection Sensors) collaboration through the Q-RADES Quantera project, in which they are a partner. The RADES project aims at detecting dark matter directly with ground-based experiments that rely on the conversion from a hypothetical dark matter particle -the axion- to a real photon inside a resonant cavity. The QRADES project aims at detecting that photon using a superconducting qubit. The RADES consortium is coordinated from the University of Zaragoza and involves teams from all over Europe.

A new search for pBH in the O1-O3 data is being explored through a population analysis, using a hierarchical Bayesian approach, where a possible subdominant population of primordial Black Holes (pBHs) on top of an astrophysical one could be identified. At the moment the analysis places upper limits on the population of primordial black holes. Once again, this is an example of collaborative effort between IFAE theory and GW groups. The results are published in M. Andrés-Carcasona et at., Phys. Rev.D 110 (2024) 2, 023040 [PRD editors suggestion].

Tamara Vázquez Schröder has been awarded the ATRAE 2024 grant to address some of the most pressing unanswered questions in particle physics, through precision measurements and searches using data from the Large Hadron Collider (LHC). Tamara, a member of the ATLAS Collaboration, has significantly contributed to the understanding of the top quark and the Higgs boson, and to the searches for new physics with the ATLAS detector.

In 2024, Andrea Wulzer, ICREA researcher at IFAE, and collaborators presented NPLM, a novel machine learning-based method to assess goodness of fit in many dimensions. The approach builds on classical hypothesis testing, using AI to generate flexible alternatives that turn the test into an absolute compatibility assessment. Benchmark studies show NPLM consistently outperforms existing methods in identifying deviations between data and theoretical models.

In 2024, Alex Pomarol and collaborators explored how causality and unitarity constrain graviton scattering in theories with U(1)-gravitational anomalies. They identified a universal scale—linked to the axion decay constant and Planck mass—where high-spin states (J ≥ 4) must appear. Their results set new bounds on axion models and large-Nc gauge theories, with implications for theories with holographic duals.

In 2024, Oriol Oujolas, IFAE researcher, and collaborators studied unstable domain wall networks as a source of gravitational waves and primordial black holes in the early universe. Using large-scale 3D simulations, they found enhanced gravitational wave emission and developed a new method to estimate PBH production from collapsing vacuum pockets. Their results show that domain wall scenarios can explain the PTA signal and, under certain conditions, account for all dark matter as asteroid-mass PBHs.

In December 2024, the European Open Science Cloud (EOSC) selected CosmoHub for inclusion in its macroroadmap, recognizing it as a key tool for advancing open science in Europe. CosmoHub is a web-based platform developed, hosted, and maintained by the Port d’Informació Científica (PIC), designed to facilitate interactive exploration and distribution of large cosmological datasets. Its integration into the EOSC roadmap highlights its strategic value in enabling accessible, scalable, and collaborative data analysis for the scientific community.

To evaluate readiness for the HL-LHC demands, a series of large-scale tests (Data Challenges) have been planned. In 2024, Tier-1 sites were tested at 25% of the expected HL-LHC requirements (DC24). During the two-week testing period, PIC successfully passed all evaluations, demonstrating its strong preparedness in terms of network capacity, infrastructure, and service reliability.

A number of network-related projects were carried out, including packet marking (tags in IPv6 traffic), improvements in global network usage monitoring within the WLCG, and testing NOTED (FTS-driven SDN, load balancing between LHCOPN and LHCONE). In particular, NOTED was successfully activated at PIC as a demonstration of load balancing between LHCOPN and LHCONE. It is triggered under high load conditions on LHCOPN to prevent saturation of the available 100 Gbps capacity, as shown in Figure 2.