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Strategy and performance of the CMS long-lived particle trigger program in proton-proton collisions at = 13.6 TeV
No full textInternational audienceIn the physics program of the CMS experiment during the CERN LHC Run 3, which started in 2022, the long-lived particle triggers have been improved and extended to expand the scope of the corresponding searches. These dedicated triggers and their performance are described in this paper, using several theoretical benchmark models that extend the standard model of particle physics. The results are based on proton-proton collision data collected with the CMS detector during 20222024 at a center-of-mass energy of 13.6 TeV, corresponding to integrated luminosities of up to 123 fb
When Primordial Black Holes Absorb During the Early Universe
No full textInternational audienceWe study the evolution of primordial black holes (PBHs) formed in the early universe in the presence of a surrounding thermal bath. By incorporating the effects of thermal absorption, we show that PBHs can undergo significant mass growth, leading to extended lifetimes and substantial deviations from the standard Hawking evaporation scenario. We find a critical collapse efficiency, , above which the PBH mass grows without bound. This correction has profound implications for both PBH-induced reheating and dark matter (DM) production. Specifically, we find that the reheating temperature can be suppressed, and the DM parameter space for the PBH reheating scenario can undergo - corrections, depending on the PBH formation mass and collapse efficiency. Moreover, our results significantly shift the parameter space in which PBHs can account for the entirety of the DM. To the best of our knowledge, this is the first comprehensive phenomenological study to incorporate thermal absorption into PBH evolution and quantify its impact on cosmological observables
An all-topology two-fluid model for two-phase flows derived through Hamilton's Stationary Action Principle
No full textInternational audienceWe present a novel multi-fluid model for compressible two-phase flows. The model is derived through a newly developed Stationary Action Principle framework. It is fully closed and introduces a new interfacial quantity, the interfacial work. The closures for the interfacial quantities are provided by the variational principle. They are physically sound and well-defined for all types of flow topologies. The model is shown to be hyperbolic, symmetrizable, and admits an entropy conservation law. Its non-conservative products yield uniquely defined jump conditions which are provided. As such, it allows for the proper treatment of weak solutions. In the multi-dimensional setting, the model presents lift forces which are discussed. The model constitutes a sound basis for future numerical simulations
Minutes-long soft X-ray prompt emission from a compact object merger
No full textInternational audienceCompact object mergers are multi-messenger sources and progenitors of some gamma-ray bursts (GRBs), primarily understood by gamma-ray observations, while poorly constrained in the prompt low-energy phase. A long-lasting X-ray emission was discussed as afterglows following several short-duration (2 s) bursts, yet this prompt X-ray component was not directly observed or confirmed. Here we report the discovery of a minutes-long (560 s) flash of soft X-rays immediately following the short (0.4 s) GRB 250704B. The long-soft bump points to a distinct phase of prompt emission in X-rays detected by Einstein Probe in an event that otherwise appear as an ordinary short GRB, showing that long-lasting X-ray emission is likely a common feature of merger-driven bursts and a promising electromagnetic counterpart to gravitational-wave sources
Filling in social “justice gaps”: Going beyond technical dynamics in just transition processes
No full textSource Agritrop Cirad (https://agritrop.cirad.fr/616440/) * Autres projets (id;sigle;titre): 101069586;BOLSTER;(EU) Bridging Organizations and marginalized communities for Local Sustainability Transitions in EuRope//International audiencePolicies that aim to protect the environment have unintended consequences on marginalized communities. Often translating into increased pressures on such communities, these consequences may be linked to top-down decision-making practices that do not consider the preferences and priorities of the marginalized in society. In this chapter, the just transition (JT) policy processes are explored for Hainaut, Belgium. The elaboration of the Territorial Just Transition Plan has guided these processes and led to three axes for the JT in the region (industry, energy, and socio-economic). However, through interviews and multi-actor forums with marginalized communities, important “justice gaps” were identified. For each axis, decision-makers prioritized technical and innovation concerns over social ones, leading to unintended consequences for marginalized communities. Looking through a socio-technical lens, this chapter concludes that JT decision-making processes led to a technical decarbonization focus in the region, but without an accompanying social shift. Considering the perspectives of marginalized communities may help fill these gaps, account for the needs of the marginalized, and support leaving no one behind in JT processes
Three-dimensional numerical simulations of product changeover: miscible and immiscible displacements in circular tubes
No full textInternational audienceWe perform three-dimensional simulations of miscible and immiscible displacements in a cylindrical pipe. For the miscible case, both laminar and turbulent displacement regimes are considered, and our numerical framework uses direct numerical simulation (DNS) and a Large Eddy Simulation (LES) approach based on a Lilly-Smagorinsky model. The dynamics of the flow are governed by the Navier-Stokes equations, coupled with a convective-diffusion equation for the concentration of the more viscous fluid when considering the miscible cases. For the immiscible laminar cases, we perform two-phase DNS considering both pinned and moving contact lines to capture the full range of immiscible dynamic behaviours. The pinned contact line reflects stationary interfaces constrained by surface heterogeneity, while the moving contact line accounts for dynamic interfacial motion influenced by viscous and capillary forces. This study shows that the viscosity contrasts between the two fluids play a significant role in determining the efficiency of 'cleaning' of a pipe containing an initially highly viscous resident fluid. When the viscosity of the displaced fluid is low, the laminar displacement flow is efficient in cleaning the pipe; however, when the viscosity increases, the laminar displacement becomes inadequate. Our numerical predictions in the turbulent regime showed that more efficient cleaning is achieved when the viscosity contrast between the two fluids is large. Lastly, our results reveal that the dynamics of a moving contact line can impact both the efficiency and the pattern of cleaning within the pipe
Three-dimensional effects on carbon capture in wavy falling films
No full textInternational audienceWave evolution in thin-film flows is highly relevant for heat and mass transfer applications, such CO2 capture in falling film absorbers. To develop a detailed understanding of potential enhancement mechanisms associated with the evolution of three-dimensional (3D) waveforms, we perform 3D direct numerical simulations of passive scalar transport in laminar-wavy film flows, using a hybrid front-tracking/level-set method to accurately resolve interfacial features. CO2 absorption is greatly enhanced in the presence of interfacial waves with the liquid-side mass transfer coefficient increasing tenfold relative to that of a flat film for the highest film Reynolds numbers (Re) studied. This is primarily due to changes in interfacial and internal flow dynamics rather than an increase in the gas-liquid interfacial area. The recirculation region present in the leading and trailing fronts of the 3D waves intensifies mass transfer, and their effectiveness increases with Re. At low Re, there is a film region beneath the wavy interface, which remains relatively undisturbed where mass transfer is dominated by diffusion. The introduction of structured substrates to promote mass transfer under these conditions is recommended. The visco-capillary ripple region, which precedes the leading and trailing fronts for sufficiently high Re, provides a relatively high degree of spanwise advection, with the mean spanwise velocity magnitude reaching around one-quarter that in the streamwise direction. This underscores the importance of solving the fully-3D problem as these effects do not have a two-dimensional analogue
Asymmetrical Latent Representation for Individual Treatment Effect Modeling
No full textConditional Average Treatment Effect (CATE) estimation, at the heart of counterfactual reasoning, is a crucial challenge for causal modeling both theoretically and applicatively, in domains such as healthcare, sociology, or advertising. Borrowing domain adaptation principles, a popular design maps the sample representation to a latent space that balances control and treated populations while enabling the prediction of the potential outcomes. This paper presents a new CATE estimation approach based on the asymmetrical search for two latent spaces called Asymmetrical Latent Representation for Individual Treatment Effect (ALRITE), where the two latent spaces are respectively intended to optimize the counterfactual prediction accuracy on the control and the treated samples. Under moderate assumptions, ALRITE admits an upper bound on the precision of the estimation of heterogeneous effects (PEHE), and the approach is empirically successfully validated compared to the state-of-the-ar
XROI-GS: Real-time XR Interactive Inspection of High-quality Objects of Interest in a 3D Gaussian Splats Scene
No full textInternational audienceWe present XROI-GS, an immersive XR framework enabling real-time exploration and interaction with complex real-world scenes. The system addresses the challenge of delivering photorealistic detail for user-specified objects within large-scale scenes while maintaining realtime XR performance. Our demonstration showcases a cultural heritage scene from the Hôtel de la Marine museum, where users can freely explore the scene space and naturally interact with historical artifacts using controller-free virtual hands. Our contribution is an automatic mechanism that significantly improves the visual quality of objects: when a user approaches or interacts with an artifact, the system enhances its resolution to increase rendering quality. In addition, we provide physically based manipulation for realistic and intuitive object handling. This framework democratizes access to fragile cultural treasures by enabling close inspection and interaction impossible in traditional museum settings, opening new possibilities for digital heritage preservation and public engagement.</div