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VENDETA: VErsatile Neutron DETector Array, a new high-resolution neutron time-of-flight measurement array
No full textInternational audienceThe VErsatile Neutron DETector Array (VENDETA) is a high-resolution time-of-flight array for neutron detection. VENDETA’s liquid scintillator detectors offer a high intrinsic efficiency for neutron detection from 100keV to 20MeV, as well as neutron-γ discrimination capabilities down to 10keVee. VENDETA was specifically designed for versatility and is relevant for a wide range of physics measurements, from prompt fission neutron spectra measurements to neutron spectroscopy studies, such as elastic and inelastic neutron scattering measurements. VENDETA was first deployed at the Los Alamos Neutron Science Center. This article will provide a detailed overview of its characteristics
UV completions of scalar-tensor EFTs
No full textInternational audienceWe study models that give rise to scalar-tensor effective field theories (EFTs) at low energies. Our framework involves massive particles of spin coupled to gravity and to a real massless scalar in the UV. Integrating out the massive states leads to a scalar-tensor EFT describing the massless graviton and scalar degrees of freedom. Using the on-shell amplitude methods and the spinor-helicity formalism, we match the two frameworks at one loop, so as to express the EFT Wilson coefficients in terms of the UV masses and coupling. We explore the space of the operators generated in the EFT, including the ones related to the scalar Gauss-Bonnet (SGB) and dynamical Chern-Simons (DCS) gravity theories. We demonstrate that, within our setup, the SGB interactions are always generated with shift-symmetry breaking operators. This is in contrast to the DCS case, where there is a unique choice that preserves the shift symmetry in the IR, corresponding to a theory of spin 1/2 fermions and a complex scalar with a Peccei-Quinn global symmetry
The Linear Point Standard Ruler with DESI DR1 and DR2 Data
No full textInternational audienceThe linear point, a purely geometric feature in the monopole of the two-point correlation function, has been proposed as an alternative standard ruler. Compared to the peak in the correlation function, it is more robust to late-time nonlinear effects at the percent level. In light of improved simulations and high quality data, we revisit the robustness of the linear point and use it as an alternative to template-based fitting approaches typically used in BAO analyses. We present the linear point measurements on galaxy samples from the first and second data releases (DR1 and DR2) of the DESI survey. We convert the linear point into a dimensionless parameter , defined as the ratio of the linear point in the fiducial cosmology and the observed value, analogous to the isotropic BAO scaling parameter used in previous BAO measurements. Using the 2nd generation of AbacusSummit mock catalogs, we find that linear point measurements are more precise when calculated in the post-reconstruction regime with 15-60% smaller uncertainties than those pre-reconstruction. We find a systematic shift in the linear point measurements compared against the isotropic BAO measurements in mocks; we attribute this to the isotropic damping parameter responsible for smearing the linear point in the nonlinear regime. We propose a sample-dependent correction that mitigates the impact of late-time nonlinear effects. While this introduces a cosmology dependence in an otherwise model-independent measurement, this is necessary given the sub-percent precision dictated by current cosmological surveys. Comparing with isotropic BAO measurements made on the DESI DR1 and DR2 galaxy samples, we find excellent agreement after applying this correction, particularly post-reconstruction. We discuss future scope regarding cosmological inference with linear point measurements
ESO Expanding Horizon White Paper: Revealing the properties of matter at supranuclear densities with gravitational waves
No full textInternational audienceUnderstanding dense matter under extreme conditions is one of the most fundamental puzzles in modern physics. Complex interactions give rise to emergent, collective phenomena. While nuclear experiments and Earth - based colliders provide valuable insights, much of the quantum chromodynamics phase diagram at high density and low temperature remains accessible only through astrophysical observations of neutron stars, neutron star mergers, and stellar collapse. Astronomical observations thus offer a direct window to the physics on subatomic scales with gravitational waves presenting an especially clean channel. Next-generation gravitational - wave observatories, such as the Einstein Telescope, would serve as unparalleled instruments to transform our understanding of neutron star matter. They will enable the detection of up to tens of thousands of binary neutron star and neutron star - black hole mergers per year, a dramatic increase over the few events accessible with current detectors. They will provide an unprecedented precision in probing cold, dense matter during the binary inspiral, exceeding by at least an order of magnitude what current facilities can achieve. Moreover, these observatories will allow us to explore uncharted regimes of dense matter at finite temperatures produced in a subset of neutron star mergers, areas that remain entirely inaccessible to current instruments. Together with multimessenger observations, these measurements will significantly deepen our knowledge of dense nuclear matter
Shape evolution in neutron-rich Rh isotopes: First measurement of negative-parity isomers in Rh
No full textInternational audienceThe β-delayed γ-ray spectroscopy of neutron-rich 117,119Rh isotopes has been investigated at the Radioactive Isotope Beam Factory of RIKEN. The 1/2− isomers in 117,119Rh have been identified for the first time. The systematics of energy differences between the 9/2+ and 1/2− states have been extended up to N=74, which shows a tendency to first increase with the neutron number N, then reach a maximum at N ≈ 68, and subsequently decrease. Self-consistent triaxial relativistic Hartree-Bogoliubov (TRHB) calculations highlight the crucial role of triaxial deformation, particularly in the positive-parity states, in driving the observed evolution of energy differences. A shape transition from axially symmetric to triaxial and back to axially symmetric deformation is suggested along the Rh isotopic chain. These findings provide new insights into the structure of neutron-rich nuclei in the A ∼ 110 region and motivate further studies of exotic isotopes in this region to explore the interplay between triaxiality and shell evolution
A new beam monitor at NFS/SPIRAL2 based on position-sensitive PPACs detecting fission fragments from <math altimg="si2.svg" display="inline" id="d1e235"><msup><mrow/><mrow><mn>238</mn></mrow></msup></math>U<math altimg="si3.svg" display="inline" id="d1e243"><mrow><mo>(</mo><mi>n</mi><mo>,</mo><mi>f</mi><mo>)</mo></mrow></math>
No full textInternational audienceA new experimental setup has been installed at the Time-Of-Flight area of the Neutrons For Science facility (NFS) at GANIL/SPIRAL2 for neutron beam monitoring. This setup consists of an array of Position-Sensitive Parallel-Plate Avalanche Counters (PS-PPACs) that detects both fission fragments in coincidence from secondary neutron-induced fission reactions in several 238U targets. The neutron energy is determined on an event-by-event basis using the Time-of-Flight method, and the reaction point within the U targets is reconstructed, enabling the measurement of the neutron beam flux and beam profile. The high transparency of the setup allows it to operate in parallel with other experiments running at NFS, thus providing an in-beam monitor of the neutron intensity. In this work, we report on the characteristics of this new setup, its operating principle, and the first results obtained using the high-intensity white-spectrum neutron beam at NFS. This beam is produced via reactions between a primary 40-MeV deuteron beam, accelerated in the SPIRAL2 LINAC, and a 8 mm-thick rotating beryllium converter target
Skyrme-Hartree-Fock-Bogoliubov mass models on a 3D mesh: V. The N2LO extension of the Skyrme EDF
No full textInternational audienceWe present BSkG5, the latest entry in the Brussels-Skyrme-on-a-Grid (BSkG) series and the first large-scale nuclear structure model based on next-to-next-to-leading order (N2LO) Skyrme energy density functional (EDF). By extending the traditional Skyrme EDF ansatz with central terms containing up to four gradients, we are able to combine an excellent global description of nuclear ground state properties with a stiff equation of state for pure neutron matter that is consistent with all astronomical observations of neutron stars. More precisely, the new model matches the accuracy of earlier BSkG models but with two parameters less: we achieve root-mean-square deviations of 0.649 MeV for 2457 atomic masses, 0.0267 fm for 810 charge radii, and 0.43 MeV for 45 primary fission barriers of actinide nuclei. We demonstrate that the complexities of N2LO EDFs are not insurmountable, even for demanding many-body calculations
Functional Ultrasound Imaging Uncovers Vascular Connectivity and Dynamics in Awake Mice During Hyperacute Stroke Phase
No full textInternational audience BACKGROUND: Acute ischemic stroke models often rely on anesthesia, which alters neurovascular coupling and limits real-time functional assessment. We tested the hypothesis that an awake mouse model of thromboembolic stroke, combined with multimodal imaging, would reveal very early cerebrovascular dynamics and connectivity changes predictive of final lesion outcomes. METHODS: Male Swiss mice (6–8 weeks old; 30–40 g; n=60) were implanted with a cranial headplate and habituated to restraint and imaging. One microliter pneumatic injection of murine thrombin (1 IU) into the distal middle cerebral artery induced in situ clot formation. Twenty minutes postocclusion, mice received intravenous rtPA (recombinant tissue-type plasminogen activator; Alteplase, 10 mg/kg; 10% bolus/90% infusion over 40 minutes, n=31) or saline (n=29). Primary outcomes included lesion volume (T2-weighted magnetic resonance imaging at 24 hours), brain perfusion (ASL magnetic resonance imaging), cerebral blood volume variations (ultrafast Doppler US imaging), resting-state connectivity, and neurovascular coupling to whisker stimulation (functional ultrasound imaging). Sample size (n=12 per group for imaging) was based on prior variability. Statistical analyses included unpaired t tests, repeated-measures ANOVA with Dunnett or Tukey post hoc, and simple linear regression; significance set at P <0.05. RESULTS: At 24 hours, rtPA reduced lesion volumes by 36.7% (10.97±4.7 versus 17.33±5.92 mm 3 in controls; t 58 =4.624; P <0.0001). ASL magnetic resonance imaging revealed a 66.5±9.9% CBF drop at 1 hour (F=48.63; P <0.0001) and a 51.2±45.1% hyperperfusion at 24 hours compared with baseline (F=11.67; P =0.0024). CBV declined by 59.2±12.9% at 10 minutes and partially recovered with rtPA at 1 hour (+87.3±30.6%; P =0.0165). Early hypoperfused area (10 minutes) predicted final lesion observed at 24 hours ( R ²=0.6465; P =0.0016). Resting-state connectivity shift of 12.0° at 10 minutes was mitigated by rtPA by 1 hour (14.8° versus 3.6°; P <0.01). Whisker-evoked CBV responses were abolished ipsilaterally at 10 minutes (−100.5±3.3%; P =0.0038) and showed partial recovery by 24 hours with rtPA (+37.2% relative to 10 minutes). At this time point, responses no longer differed significantly from baseline ( P =0.093), indicating a modest but functionally meaningful recovery despite marked interindividual variability. CONCLUSIONS: Awake thromboembolic stroke model with early functional ultrasound imaging completed with magnetic resonance imaging uncovers rapid blood flow perturbations and connectivity disruptions that are sensitive to rtPA and predictive of final lesion outcome. This platform enhances translational relevance by enabling hypothesis-testing of novel thrombolytics under physiologically intact conditions. </jats:sec
Weak Lensing Mass Calibration of the ACT DR5 Galaxy Clusters with the DES Year 3 Weak Lensing Data
No full textInternational audienceWe use weak gravitational lensing measurements from Year 3 Dark Energy Survey data to calibrate the masses of 443 galaxy clusters selected via the Sunyaev-Zel'dovich effect from Atacama Cosmology Telescope Data Release 5 maps of the cosmic microwave background. We incorporate redshift and SZ measurements for individual clusters into a hierarchical model for the stacked lensing signals and perform Bayesian analyses to constrain the hydrostatic mass bias of the clusters. Our treatment of systematic uncertainties includes a prescription for measuring and accounting for the weak lensing boost factor, consideration of a miscentering effect, as well as marginalization over uncertainties in the source galaxy photometric redshift distributions and shear calibration. The resultant constraints on the normalization of the mass-observable relation have a precision of approximately 7%, with the mean WL halo mass of . We measure the bias between the true cluster mass and the mass estimated from the SZ signal based on an X-ray--calibrated scaling relation assuming hydrostatic equilibrium, to be over the full sample. When splitting the clusters into high (=0.43-0.70) and low (=0.15-0.43) redshift bins, we measure and , respectively. When introducing additional freedom in redshift and mass to the hydrostatic bias model, we find that decreases with redshift (with the power law of , 99.95% confidence), consistent with findings from other recent studies, while we do not find any significant trend in mass. We also demonstrate that our result is robust against various systematics. The weak-lensing mass calibration presented in this study will be a useful tool for using the ACT clusters as probes of astrophysics and cosmology
Machine-learning techniques for model-independent searches in dijet final states
No full textInternational audienceAnomaly detection methods used in a recent search for new phenomena by CMS at the CERN LHC are presented. The methods use machine learning to detect anomalous jets produced in the decay of new massive particles. The effectiveness of these approaches in enhancing sensitivity to various signals is studied and compared using data collected in proton-proton collisions at a center-of-mass energy of 13 TeV. In an example analysis, the capabilities of anomaly detection methods are further demonstrated by identifying large-radius jets consistent with Lorentz-boosted hadronically decaying top quarks in a model-agnostic framework