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First evidence of violation in beauty baryon to charmonium decays
No full textInternational audienceA study of the difference in the asymmetries between and decays, , is performed using proton-proton collision data collected by the LHCb experiment in the years 2015--2018, corresponding to an integrated luminosity of . This quantity is measured to be , where the first uncertainty is statistical and the second is systematic. When combined with the previous LHCb result, a value of is obtained, corresponding to a significance of against the symmetry hypothesis. Studies of triple-product asymmetries, which provide an additional probe of violation, show no significant deviation from symmetry
A strong-weak duality for the 1d long-range Ising model
No full textInternational audienceWe investigate the one-dimensional Ising model with long-range interactions decaying as . In the critical regime, for , this system realizes a family of nontrivial one-dimensional conformal field theories (CFTs), whose data vary continuously with . For s>1 the model has instead no phase transition at finite temperature, as in the short-range case. In the standard field-theoretic description, involving a generalized free field with quartic interactions, the critical model is weakly coupled near but strongly coupled in the vicinity of the short-range crossover at . We introduce a dual formulation that becomes weakly coupled as . Precisely at , the dual description becomes an exactly solvable conformal boundary condition of the two-dimensional free scalar. We present a detailed study of the dual model and demonstrate its effectiveness by computing perturbatively the CFT data near , up to next-to-next-to-leading order in , by two independent approaches: (i) standard renormalization of our dual field-theoretic description and (ii) the analytic conformal bootstrap. The two methods yield complete agreement
Interhemispheric and Latitudinal Variability of Ionospheric Disturbances During the 19-20 December 2015 Geomagnetic Storm: Insights from the South American Sector
No full textInternational audienceThis study investigates the response of the South American ionosphere to the December 19-20, 2015, geomagnetic storm using multi-instrument satellite and ground-based data. An interplanetary shock triggered prompt penetration electric fields (PPEFs) during the storm's initial phase, initiating rapid DP2 currents and significant equatorial electrojet (EEJ) fluctuations, particularly in Jicamarca, Peru. Our analysis shows that dayside field-aligned currents (FACs) are the primary drivers of the observed DP2 fluctuations. The South Atlantic Magnetic Anomaly (SAMA) also induced a westward geomagnetic gradient-induced current at the equatorward boundary, which suppressed the EEJ current at São Luiz during the magnetically quiet period. During the storm's main phase, eastward PPEFs enhanced ionospheric irregularities at several Global Positioning Satellite (GPS) stations: Sao Luiz (14.8%), Cuiaba (11.4%), and Jatai (15.5%) in Brazil; Tucuma (33.6%) and Rio Grande (33.2%) in Argentina; and all Peruvian GPS stations (5.8 -57.6%), with Arequipa showing the highest percentage. Conversely, irregularities were inhibited at Eusebio (-31.5%), São José dos Campos (-11.8%), and Campo Grande (-4.8%) in Brazil, and Rosario (-9.4%) and Villegas (-0.8%) in Argentina, relative to a magnetically quiet day, which was attributed to the interplay between westward disturbance dynamo electric fields (DDEF) and PPEF. Joule heating, peaking at 14:35 UT on 20 December drove equatorward disturbance winds that generated the DDEF and modulated irregularities during the recovery phase. Westward DDEF suppressed post-sunset irregularities across most Brazilian and Argentine stations (-50.2% to -10.1%), but slightly enhanced post-midnight ionospheric irregularities at Cuiabá (+4.3%) and Tucuma (+21.1%). All Peruvian stations recorded post-midnight enhancements (+14.8% to +136.7%), with Arequipa showing the highest increase. We quantified the delayed magnetic response of the disturbance dynamo (Ddyn) relative to Joule heating, revealing propagation delays of approximately 6, 8.5, and 8.2 h in Brazil, Argentina, and Peru, respectively. Ddyn exhibited strong spatiotemporal variability, including spatial anomalies associated with the SAMA. The Peruvian sector dominated the Ddyn power (59.0%), followed by Brazil (35.1%) and Argentina (5.9%). Evidence of interhemispheric FAC asymmetry, attributed to seasonal variability, was also observed. These findings significantly advance our understanding of storm-time lowlatitude electrodynamics and their regional variability
First exclusive reconstruction of the B, B, and B mesons and precise measurement of their masses
No full textInternational audienceUsing proton-proton collision data collected by the CMS experiment at = 13 TeV in 20162018, corresponding to an integrated luminosity of 140 fb, the first full reconstruction of the three vector B meson states, B, B, and B, is performed. The mass differences between the excited mesons and their corresponding ground states are measured to be = 45.277 0.039 0.027 MeV, = 45.471 0.056 0.028 MeV, and = 49.407 0.132 0.041 MeV, where the first uncertainties are statistical and the second are systematic. These results improve on the precision of previous measurements by an order of magnitude
Quantum vs. semiclassical description of in-QGP quarkonia in the quantum Brownian regime
No full textInternational audienceIn this work, we explore the range of validity of the semiclassical approximation of a quantum master equation designed to describe the dynamics in a quark gluon plasma at various temperatures, in the quantum Brownian regime. We perform a comparative study of various properties, e.g. the charmonia yield, of the Wigner density obtained with the Lindblad equation and with the associated semiclassical Fokker-Planck equation. The semiclassical description is found to reproduce with a remarkable accuracy the results obtained through the full quantum description. We show that, to a large extent, this can be attributed to the non-unitary components of the dynamics that result from the contact of the subsystem with the thermal bath, leading to a rapid classicalization of the subsystem
Steady Collapse of Uranus' Exosphere After 1998 to the Present Decade
No full textInternational audienceUranus' thermospheric temperature decreased from ∼800K in 1986 to ∼450K in 2022 as determined from observations of H3 + and H2 infrared emissions. Spitzer 2007 lower atmosphere observations do not emulate this cooling trend. Here we show that the atomic H Lyman ⍺ emission from the disk of Uranus observed by HST from 2011 to 2022 are not consistent with radiative transfer models based on a constant atmospheric structure retrieved from the Voyager 2 flyby of 1986. Instead, the optical depth of the H column matching the Uranus Lyman ⍺ disk brightness decreased after 1998, consistent with the long‐term cooling trend. This decrease is irrespective of auroral activity. While the origin of the cooling is poorly understood, it indicates that the density and extent of the Uranssian exosphere changes on a time scale of years impacting the atmospheric structure, the magnetospheric proton source, and exospheric drag on the inner rings
Extremely Metal-Poor Galaxies in DESI DR1: Connections to Galaxies in the Early Universe
No full textInternational audienceExtremely Metal-Poor Galaxies (XMPGs), defined as having metallicities below 10% of the solar value, are considered possible local analogs to primordial systems and offer a unique window into early galaxy evolution. This study presents a large-scale search for XMPGs using data from the Dark Energy Spectroscopic Instrument DR1, systematically evaluating their resemblance to high-redshift galaxies. From a parent sample of over 14 million galaxies, we identify 656 (551 new) confirmed XMPGs and 767 (670 new) high-quality candidates via the direct method. Results reveal that XMPGs follow a distinct star-forming main sequence (SFMS) that is elevated and shallower than that of the comparing star-forming galaxies. Notably, at higher stellar masses (), the XMPG SFMS converges with the sequence observed in high-redshift galaxies by James Webb Space Telescope (JWST), indicating that mature XMPGs sustain star formation rates comparable to their primordial counterparts. Furthermore, XMPGs consistently deviate below the local fundamental metallicity relation, mirroring high-redshift galaxy behavior. These findings demonstrate that XMPGs not only exhibit low metallicities but also preserve scaling relations characteristic of the early Universe, confirming their potential value as local laboratories for studying early galaxy formation processes
Développement d'électrolytes polymères nanoporeux pour les batteries au lithium métal
No full textInternational audienceSeparators used in lithium batteries (LiBs) physically separate the electrodes to prevent short circuits, while allowing lithium ions (Li+) to move freely through the pores of the separators. As a critical component of LiBs, separators directly impact battery performance. Macroporous polyolefin-based membranes have been widely used as separators in LiBs due to their mechanical strength and adequate electrochemical stability. However, these separators suffer from inherent limitations, such as poor wettability, low liquid electrolyte loading as well as low thermal stability. Poor electrolytes wettability and absorption hinder Li+ transport, degrading battery performance during charge and discharge cycles. In addition, the low thermal stability of polyolefin separators increases the risk of internal short circuits at high temperatures, raising significant safety concerns1.On the other hand, confining liquid electrolytes or poly(ethhylene oxide)/Li salt electrolytes within nanoporous membranes enhanced both ionic conductivity and cycling performance2,3. However, the pore wall chemistry and the pores density of the reported nanoporous membranes cannot be easily modulated. In the present work, we propose an innovative approach based on the self-assembly of block copolymers (BCPs) to fabricate porous polymer electrolyte membranes with oriented nanometric cylindrical pores perpendicular to the electrodes. This approach provides a versatile platform for tailoring the size and geometry of nanopores at large-scale as well as enabling selective functionalization of voided channels. The BCPs used in this work consist of a sacrificial block – polyethylene oxide (PEO) – and a matrix block, that is a random copolymer of styrene and isoprene: poly(styrene-r-isoprene) (PSI) (Fig. 1A). These BCPs were synthesized via nitroxide-mediated polymerization to achieve low dispersity (Ð<1.3). The pore size was directly controlled by the length of the PEO block (ranging from 5 to 20 kg/mol), while the mechanical properties of the membranes were conferred by the cross-linked PSI matrix. Thin films, approximatively tens of micrometers thick, exhibited excellent nanostructuration in various morphologies depending on the BCP composition (Fig. 1B-C). The PEO block was subsequently removed from the UV-cross-linked films via acid hydrolysis, resulting in nanoporous membranes. Extensive chemical and physical characterization were performed using a combination of techniques (AFM, SEM, SAXS ,SANS,…) to fully characterize our membranes, both empty and filled with non-flammable liquid electrolytes.This communication will feature on synthesis, self-assembly and characterization of our BCPs.Bibliography : (1) Adv. Sci. 2021, 8 (7), 2003096. https://doi.org/10.1002/advs.202003096.(2) Energy Storage Mater. 2025, 75,104045.https://doi.org/10.1016/j.ensm.2025.104045.(3) Batteries. Nat. Nanotechnol. 2019, 14 (7), 705–711. https://doi.org/10.1038/s41565-019-0465-3
Identification of transdiagnostic phenomena among patients, the general population, relatives, and mental health professionals using topic modeling techniques
No full textInternational audienceIntroduction Recent research has highlighted the limitations of the categorical approach to mental disorders and has increasingly supported the development of a transdiagnostic perspective. This emerging approach focuses on common distal factors (circumstantial, biological, and social) and psychological processes that contribute to psychological suffering across a range of disorders, as well as on the resulting psychological symptoms. The present study aims to identify transdiagnostic distal factors, psychological processes, and symptoms by analyzing narratives through topic modeling—an unsupervised machine learning technique, specifically within Natural Language Processing (NLP). Topic modeling enables the automatic extraction of latent themes from unstructured text, making it possible to identify psychological patterns grounded in patients’ lived experiences. Methods We recruited four groups of participants: Patients diagnosed with a psychiatric disorder ( N = 445), Individuals from the general population ( N = 570), Relatives of patients with psychiatric disorders ( N = 354), and Mental health professionals ( N = 131). Participants answered open-ended questions exploring the causes of psychological suffering, their wishes for change, and their previous experiences with psychotherapy. Results We identified 258 topics, which were organized into 12 overarching themes. The most prominent topics concerned Emotional and Psychological Difficulties , Family and Social Relationships , and Therapeutic Processes . Each theme showed a comparable prevalence across the different diagnostic categories, supporting the transdiagnostic nature of these phenomena. Conclusion Topic modeling can be used effectively to identify transdiagnostic distal factors, psychological processes, and symptoms from diverse narratives. This approach tends to provide a novel means of supporting the relevance and validity of the transdiagnostic perspective