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A Linear Collider Vision for the Future of Particle Physics
No full textInternational audienceIn this paper we review the physics opportunities at linear colliders with a special focus on high centre-of-mass energies and beam polarisation, take a fresh look at the various accelerator technologies available or under development and, for the first time, discuss how a facility first equipped with a technology mature today could be upgraded with technologies of tomorrow to reach much higher energies and/or luminosities. In addition, we will discuss detectors and alternative collider modes, as well as opportunities for beyond-collider experiments and R&D facilities as part of a linear collider facility (LCF). The material of this paper will support all plans for linear colliders and additional opportunities they offer, independently of technology choice or proposed site, as well as R&D for advanced accelerator technologies. This joint perspective on the physics goals, early technologies and upgrade strategies has been developed by the LCVision team based on an initial discussion at LCWS2024 in Tokyo and a follow-up at the LCVision Community Event at CERN in January 2025. It heavily builds on decades of achievements of the global linear collider community, in particular in the context of CLIC and ILC
Probing the flavour structure of dimension-6 EFT operators in multilepton final states in proton-proton collisions at = 13 TeV
No full textInternational audienceAn analysis of the flavour structure of dimension-6 effective field theory (EFT) operators in multilepton final states is presented, focusing on the interactions involving Z bosons. For the first time, the flavour structure of these operators is disentangled by simultaneously probing the interactions with different quark generations. The analysis targets the associated production of a top quark pair and a Z boson, as well as diboson processes in final states with at least three leptons, which can be electrons or muons. The data were recorded by the CMS experiment in the years 20162018 in proton-proton collisions at a centre-of-mass energy of 13 TeV and correspond to an integrated luminosity of 138 fb. Consistency with the standard model of particle physics is observed and limits are set on the selected Wilson coefficients, split into couplings to light- and heavy-quark generations
A benchmark of expert-level academic questions to assess AI capabilities
No full textInternational audienceBenchmarks are important tools for tracking the rapid advancements in large language model (LLM) capabilities. However, benchmarks are not keeping pace in difficulty: LLMs now achieve more than 90% accuracy on popular benchmarks such as Measuring Massive Multitask Language Understanding1, limiting informed measurement of state-of-the-art LLM capabilities. Here, in response, we introduce Humanity’s Last Exam (HLE), a multi-modal benchmark at the frontier of human knowledge, designed to be an expert-level closed-ended academic benchmark with broad subject coverage. HLE consists of 2,500 questions across dozens of subjects, including mathematics, humanities and the natural sciences. HLE is developed globally by subject-matter experts and consists of multiple-choice and short-answer questions suitable for automated grading. Each question has a known solution that is unambiguous and easily verifiable but cannot be quickly answered by internet retrieval. State-of-the-art LLMs demonstrate low accuracy and calibration on HLE, highlighting a marked gap between current LLM capabilities and the expert human frontier on closed-ended academic questions. To inform research and policymaking upon a clear understanding of model capabilities, we publicly release HLE at https://lastexam.ai
Simultaneous probe of the charm and bottom quark Yukawa couplings using ttH events
No full textInternational audienceA search for the standard model Higgs boson decaying to a charm quark-antiquark pair, H , produced in association with a top quark-antiquark pair (H) is presented. The search is performed with data from proton-proton collisions at = 13 TeV, corresponding to an integrated luminosity of 138 fb. Advanced machine learning techniques are employed for jet flavor identification and event classification. The Higgs boson decay to a bottom quark-antiquark pair is measured simultaneously and the observed H bb event rate relative to the standard model expectation is 0.91. The observed (expected) upper limit on the product of production cross section and branching fraction (H)(H ) is 0.11 (0.13) pb at 95% confidence level, corresponding to 7.8 (8.7) times the standard model prediction. When combined with the previous search for H via associated production with a W or Z boson, the observed (expected) 95% confidence interval on the Higgs-charm Yukawa coupling modifier, , is 3.5 (2.7), the most stringent constraint to date
Search for decays at the LHCb experiment with Run 2 data
No full textInternational audienceA search for the lepton-flavour-violating decay is carried out using data collected by the LHCb experiment between 2016 and 2018 in proton-proton collisions at the LHC at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4 fb. An upper limit of is set at the 90% (95%) confidence level on the branching fraction of the decay
Low latency global carbon budget indicates reduced land carbon sink in the year 2024
No full textInternational audienceIn 2024, the atmospheric CO2 growth rate based on the globally averaged marine boundary layer (MBL) observations from the National Oceanic and Atmospheric Administration (NOAA) network reached 3.73 ± 0.08 ppm yr−1, marking a record high since continuous measurements began in 1959 (Fig. 1a) [1]. The whole-atmosphere growth rate derived from independent OCO-2 satellite observations for 2024 was 3.20 ± 0.1 ppm yr−1 using the Growth Rates from Satellite Observations data-driven approach (GRESO) from Ref. [2], the highest value of the OCO-2 record since 2015. The whole-atmosphere growth rate derived from our flux inversion models assimilating OCO-2 observations mainly over land for 2024 was 3.23 ± 0.12 ppm yr−1, thus unsurprisingly being almost equal to GRESO and less than the MBL stations but still a record high in the OCO-2 inversions record since 2015. This 38.15% increase in the CO2 growth rate between 2023 and 2024 occurred despite fossil fuel CO2 emissions increasing by only 0.85% [3]. This highlights an unprecedented weakening of the net carbon uptake on land and ocean. Net land uptake is defined here as the sum of non-fossil land CO2 fluxes including photosynthesis, respirations, fire, rivers and land-use change emissions. Here, we present a low latency global and regional carbon budget for 2024, using top-down inversions and bottom-up models, revealing a strong weakening of the global net land carbon sink and widespread transitions of terrestrial regions from carbon sinks to sources
Non-Exchangeable Mean Field Markov Decision Processes with common noise : from Bellman equation to quantitative propagation of chaos
No full textWe study infinite-horizon Markov Decision Processes (MDPs) with a continuum of heterogeneous agents interacting through a common noise, without assuming exchangeability. We introduce the framework of Conditional Non-Exchangeable Mean Field MDPs (CNEMF-MDPs) in both a strong formulation and a label-state formulation. We establish the equivalence between these two formulations by showing that the control problem can be lifted to a standard MDP defined on the Wasserstein space P λ (I ×X ), where I denotes the label (heterogeneity) space, X is the individual state space, and λ specifies the fixed distribution of agent labels. Within this framework, we characterize the value function as the unique fixed point of an appropriate Bellman operator acting on P λ (I × X ).Our second contribution is a quantitative analysis of the propagation of chaos for this non-exchangeable setting with common noise. We derive sharp finite-population bounds by comparing the Bellman operator of the finite N -agent MDP, defined on the high-dimensional space X N , with its infinite-agent counterpart. This comparison yields explicit constructions of near-optimal policies for the N -agent system from -optimal policies of the limiting CNEMF-MDP.</div
Scalable fabrication of high-quality WS2 thin films via solution processing for NO2 sensing
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Constraints on gravitational waves from the 2024 Vela pulsar glitch
No full textInternational audienceAmong known neutron stars, the Vela pulsar is one of the best targets for gravitational-wave searches. It is also one of the most prolific in terms of glitches, sudden frequency changes in a pulsar's rotation. Such glitches could cause a variety of transient gravitational-wave signals. Here we search for signals associated with a Vela glitch on 29 April 2024 in data of the two LIGO detectors from the fourth LIGO--Virgo--KAGRA observing run. We search both for seconds-scale burst-like emission, primarily from fundamental (f-)mode oscillations, and for longer quasi-monochromatic transients up to four months in duration, primarily from quasi-static quadrupolar deformations. We find no significant detection candidates, but for the first time we set direct observational upper limits on gravitational strain amplitude that are stricter than what can be indirectly inferred from the overall glitch energy scale. We discuss the short- and long-duration observational constraints in the context of specific emission models. These results demonstrate the potential of gravitational-wave probes of glitching pulsars as detector sensitivity continues to improve
Search for the pair production of long-lived supersymmetric partners of the tau lepton in proton-proton collisions at = 13 TeV
No full textInternational audienceGauge-mediated supersymmetry-breaking models provide a strong motivation to search for a supersymmetric partner of the tau lepton (stau) with a macroscopic lifetime. Long-lived stau decays produce tau leptons that are displaced from the primary proton-proton interaction vertex, leading to an unconventional signature. This paper presents a search for the direct production of long-lived staus decaying within the CMS tracker volume in proton-proton collisions at = 13 TeV, performed for the first time with an identification algorithm based on a graph neural network dedicated to displaced tau leptons. The data sample, corresponding to an integrated luminosity of 138 fb, was recorded with the CMS experiment at the CERN LHC between 2016 and 2018. This search excludes, at 95% confidence level, stau masses, m_\tildeτ, in the 126260 (906425) GeV range for a proper decay length of 50 mm in the maximally mixed (mass-degenerate) scenario, while for m_\tildeτ = 200 GeV, stau proper decay lengths are excluded in the range 2194 (6333) mm. These results improve the exclusion limits compared to previous searches, and extend the parameter space explored in the context of supersymmetry