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Observation of decays
No full textInternational audienceSearches are presented for decays, where is a charmed meson and is a charged pion or kaon, using collision data collected by the LHCb experiment corresponding to an integrated luminosity of . The decays , and are observed for the first time. Their branching fractions, expressed as ratios relative to that of the decay, are determined to be \begin{align*} \mathcal{R}(B_c^+\to D^+ K^+π^-) =(1.96 \pm 0.23\pm 0.08 \pm 0.10)\times 10^{-3},&\\ \mathcal{R}(B_c^+\to D^{*+} K^+π^-) =(3.67 \pm 0.55 \pm 0.24\pm 0.20)\times 10^{-3},&\\ \mathcal{R}(B_c^+\to D_s^+ K^+ K^-) =(1.61 \pm 0.35\pm 0.13\pm 0.07)\times 10^{-3}, \end{align*} where the first uncertainty is statistical, the second is systematic, and the third is due to the limited precision on the -meson branching fractions. The decay channels proceed primarily through excited or resonances or mesons, and open a new avenue for studies of charge-parity violation in beauty mesons
Boundary output feedback stabilization of heat-ODE cascades
No full textInternational audienceThis paper studies the boundary output feedback stabilization of heat-ODE cascades. We consider a either Dirichlet or Neumann boundary control input that applies at the left boundary of the heat equation. The PDE enters into the ODE through a either Dirichlet or Neumann trace at the right boundary of the PDE. The system output applies solely to the ODE. The reported approach relies on spectral reduction methods and is conducted through a detailed study of the eigenelements of the heat-ODE cascade. We show that the adopted approach can always be successfully implemented for achieving the output feedback exponential stabilization of heat-ODE cascades in the either L2 -or H1 -norm
Evidence for the absence of a relationship between inflammation and cognition in a cohort of 1565 individuals with bipolar spectrum disorders: a Bayesian analysis of network
No full textInternational audiencePrevious studies have reported variable associations between peripheral inflammatory markers and cognitive functioning in individuals with bipolar spectrum disorders (BSD), with some identifying significant links and others finding no relationship. Such inconsistencies raise important questions about the role of inflammation in cognitive impairment among individuals with BSD. This study aims to investigate the relationship between peripheral inflammatory markers and cognitive function in a clinical sample of individuals with BSD using a Bayesian network analysis framework. We analyzed data from a large cohort (n = 1565) focusing on hsCRP and a subsample (n = 249) that included concurrent assessments of additional cytokines including Interleukin-6 and Tumor Necrosis Factor-alpha. A Bayesian approach was utilized to quantify uncertainty regarding the presence or absence of associations between inflammation and cognitive function. Our findings revealed no significant associations between inflammatory markers and cognitive performance in both samples. Strong evidence was found supporting the absence of association, with network analysis indicating distinct clusters for cognitive and inflammatory variables, suggesting they function as independent constructs with limited interactions. In our clinical sample of individuals with BSD, our findings do not support a direct association between some inflammatory markers and cognition, aligning with studies that found minimal or no associations. Our study emphasizes the importance of utilizing Bayesian methods to assess these relationships rigorously and suggests further exploration of individual differences and subgroup effects in future research
Data sorting modes of phoswich detector array
No full textInternational audienceThe different data sorting modes of the phoswich detector array PARIS used for detecting high-energy (410 MeV) rays are investigated. The characteristics including time resolution, energy resolution and detection efficiency under various modes are studied. The present study shows that PARIS has capabilities of rejecting escape and pileup events. Compared with the 2"2"2" LaBr(Ce) detector \cite{CIEMALA200976}, even in individual mode, PARIS provides significant suppression of single- and double-escape peaks and reduces background via vetoing function of the outer-volume NaI(Tl) crystals. In contrast to the common approach of adding back the energies in LaBr(Ce) and NaI(Tl) to increase the detection efficiency of the full-energy peak, using NaI(Tl) as a veto shield provides a superior trade-off for applications where spectral purity is essential. Employing add-back analysis within each cluster of nine phoswiches or between all phoswiches could enhance full-energy peak efficiency and further suppress escape peaks and background. Applying a multiplicity condition provides a further suppression but simultaneously lowers the statistics of full-energy peaks. Notably, the methods presented in this work refer specifically to the -decay experiment of Ga conducted with three PARIS clusters comprising 27 phoswich detectors, rather than to a general report on the PARIS array or its overall performance
Prescribing the best decay rate of the wave equation using internal delayed feedback damping
No full textInternational audienceIn this paper, we investigate the stabilization of the damped wave equation through the use of an internal feedback mechanism incorporating time delay. This work builds upon the partial pole placement paradigm, a recent theoretical framework originally developed for functional differential equations, which enables the selective assignment of eigenvalues within a prescribed region of the complex plane. Using this approach, we design an internal delayed feedback law that guarantees the exponential stabilization of the resulting closed-loop system. A distinctive feature of our control strategy lies in its ability to prescribe the optimal exponential decay rate for each modal cluster, thereby achieving the fastest possible stabilization consistent with the system's spectral limitations. This can be achieved regardless of the stabilizability domain being delay-independent or delay-dependent. This allows for a highly efficient control mechanism tailored to the specific dynamical behavior of the wave equation. To illustrate the practical relevance of our theoretical findings, we apply the proposed method to the control of transverse vibrations in a taut string. Numerical simulations confirm the robustness and effectiveness of the feedback design, underscoring its potential for broader applications in the control of distributed parameter systems with delay effects
Connecting ground-state properties of Li to each other and to scattering data
No full textInternational audienceWe examine the relationship between the Asymptotic Normalization Coefficient (ANC) of Li and other low-energy observables in the -deuteron system. Our analysis uses a set of calculations carried out within the {\it ab initio} No Core Shell Model with Continuum (NCSMC) using a variety of inter-nucleon interactions and basis sizes, and yielding Li deuteron separation energies between 1.3 and 1.8 MeV [Phys. Rev. Lett. 129, 042503 (2022)]. These NCSMC calculations show that the square of the ANC is strongly correlated with the separation energy over this range. In this work, we investigate the origin of this correlation using the phenomenological -matrix, a single-channel potential and a perturbative approach. We show that this correlation occurs because the depth of the -deuteron central potential changes by only a small relative amount as the separation energy varies. We then investigate if the ANC can be accurately extracted from -deuteron phase shifts in an ideal case in which low-energy data are available and there are no experimental errors. We find that both -matrix and Coulomb-modified effective-range theory (CM-ERE) yield extracted ANCs close to, although not exactly equal to, the true value, provided the extrapolation is constrained by the known position of the bound-state pole and at least three terms are included in the fit function. The -matrix approach converges faster than the CM-ERE as the number of parameters increases and is also more robust against the inclusion of low-energy and high-energy phase shift data. Finally, our study also shows that a naive quantification of uncertainties by comparing different truncations used in both theories is not accurate, and suggests the accuracy of ANCs extracted from phase shift data needs further investigation
Evidence of Energy Injection in the Short and Distant GRB 250221A
No full textInternational audienceWe present the photometric and spectroscopic analysis of the short-duration GRB 250221A ( s), using a data set from the optical facilities COLIBRÍ, the Harlingten 50 cm Telescope, and the Very Large Telescope. We complement these observations with data from the \textit{Neil Gehrels Swift Observatory} and the \textit{Einstein Probe}, as well as radio observations from the Very Large Array. GRB 250221A is among the few short GRBs with direct afterglow spectroscopy, which gives a secure redshift determination of and allows the unambiguous identification of the host as a galaxy with a star-formation rate of . The X-ray and optical light curves up to ks (where refers to the GRB trigger time) are well described by forward-shock synchrotron emission in the slow-cooling regime within the standard fireball framework. However, at days, both the X-ray and optical bands exhibit an excess over the same interval, which we interpret as evidence of energy injection into a jet with a half-opening angle of through a refreshed shock powered by late central engine activity or a radially stratified ejecta. The burst properties (duration, spectral hardness, peak energy, and location in the Amati plane) all favour a compact binary merger origin. However, our modelling of the afterglow suggests a dense circumburst medium ( cm), which is more typical of a Collapsar environment. This tension over the classification of this burst (short-hard vs. long-soft) as inferred from the prompt and afterglow emissions makes GRB~250221A an unusual event and underscores the limitations of duration-based classifications and the importance of multi-wavelength, time-resolved follow-up observations
Measurement of asymmetry in decays with the LHCb Upgrade I detector
No full textInternational audienceA measurement of asymmetry in decays is reported, based on a data sample of proton-proton collisions collected with the LHCb Upgrade I detector in 2024 at a centre-of-mass energy of TeV, corresponding to an integrated luminosity of . The decay is used as calibration channel to cancel residual detection and production asymmetries. The time-integrated asymmetry for the mode is measured to be where the first uncertainty is statistical, and the second is systematic. This is the most precise determination of this quantity to date
Directional light scattering in Mie-resonant Si particles with ultra-thin Au shells
No full textInternational audienceMetamaterial research has sought to create nanostructures with strong directional optical scattering to control light propagation at the nanoscale. Core–shell architectures comprised of both resonant cores and resonant shells are suggested as candidate particles in which the spectral overlap of the electric and magnetic dipoles is controlled to create strong directional scattering. In this study, Au-decorated Si core–shell (Si@Au) particles are presented, studying the role of the architecture (particulate, discontinuous shells vs continuous) and dimensions of the shell. The core–shell particles are synthesized by first creating Si particles, through the thermal disproportionation of hydrogen silsesquioxane (HSQ), which are then decorated with ≈4 nm diameter Au nanoparticles. The resonant behavior of the core–shell particles is characterized using electron energy-loss spectroscopy mapping and optical single-particle scatter spectroscopy. These observations are supported by T-matrix simulations and Mie-theory calculations of the scattering spectra, which show that, compared to Si, Si@Au particles demonstrate a dampened magnetic dipole resonance for smaller Si core diameters (100–130 nm) and an enhanced magnetic dipole resonance for larger Si core sizes (150–200 nm). The study indicates that the previously reported hybridized modes do not exist in particulate Au shells around a Si core and can only exist in continuous plasmonic shells. Thus, it is shown here how important it is to be as precise as possible regarding the nanomaterial architecture used in simulations. No configuration of Si@Au core–shell particles with a particulate shell could be found that strongly enhanced directional scattering, and a continuous shell may do so only modestly. However, the simulations show that the synthesis of thin, continuous Ag shells might represent an alternative route towards achieving good directional scattering properties.</p
Sea Surface Wave Remote Sensing
No full textInternational audienceAs a type of gravity wave travels at the interface between atmosphere and ocean, sea surface wave is a fundamental dynamic phenomenon which must be considered in oceanographic research, offshore engineering and maritime shipping etc. With the rapid development of space science and technology, satellite remote sensing has become an indispensable technology to observe and understand sea surface waves due to its advantages of global coverage, all-weather and all-day characteristics. This chapter introduces the characterization methods and main parameters of sea surface waves, the main spaceborne microwave payloads and observation principles of sea surface waves, and the main scientific and operational applications of satellite surface wave data