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Observation of production at 13 TeV with the ATLAS detector
No full textInternational audienceThis paper presents the first observation of top-quark pair production in association with two photons (). The measurement is performed in the single-lepton decay channel using proton-proton collision data collected by the ATLAS detector at the Large Hadron Collider. The data correspond to an integrated luminosity of 140 fb recorded during Run 2 at a centre-of-mass energy of 13 TeV. The production cross section, measured in a fiducial phase space based on particle-level kinematic criteria for the lepton, photons, and jets, is found to be , corresponding to an observed significance of 5.2 standard deviations. Additionally, the ratio of the production cross section of to top-quark pair production in association with one photon is determined, yielding
GPU-accelerated LISA parameter estimation with full time domain response
No full textInternational audienceWe conduct the first full Bayesian inference analysis for LISA parameter estimation incorporating the effects of subdominant harmonics and spin-precession through a full time domain response. The substantial computational demands of using time domain waveforms for LISA are significantly mitigated by implementing a novel Python version of the IMRPhenomT family of waveform models and the LISA response with GPU acceleration. This time domain response alleviates the theoretical necessity of developing specific transfer functions to approximate the LISA response in the Fourier domain for each specific type of system and allows for the use of unequal arms configurations and realistic LISA orbits. Our analysis includes a series of zero-noise injections for a Massive Black Hole Binary with aligned and precessing spins. We investigate the impact of including subdominant harmonics, compare equal and unequal arm configurations, and analyze different Time-Delay-Interferometry (TDI) configurations. We utilize full and uniform priors, with a lower frequency cutoff of 0.1mHz, and a signal duration of approximately two months, sampled every 5 seconds. The sampler is initialized based on Fisher estimates. Our results demonstrate LISA capability to measure the two spin magnitudes and the primary spin tilt angle, alongside sky localization, with percent-level precision, while component masses are determined with sub-percent accuracy
Euclid: Optimising tomographic redshift binning for 32pt power spectrum constraints on dark energy
No full textInternational audienceWe present a simulation-based method to explore the optimum tomographic redshift binning strategy for 3x2pt analyses with Euclid, focusing on the expected configuration of its first major data release (DR1). To do this, we 1) simulate a Euclid-like observation and generate mock shear catalogues from multiple realisations of the 3x2pt fields on the sky, and 2) measure the 3x2pt Pseudo-Cl power spectra for a given tomographic configuration and derive the constraints that they place on the standard dark energy equation of state parameters (w0, wa). For a simulation including Gaussian-distributed photometric redshift uncertainty and shape noise under a LambdaCDM cosmology, we find that bins equipopulated with galaxies yield the best constraints on (w0, wa) for an analysis of the full 3x2pt signal, or the angular clustering component only. For the cosmic shear component, the optimum (w0, wa) constraints are achieved by bins equally spaced in fiducial comoving distance. However, the advantage with respect to alternative binning choices is only a few percent in the size of the (w0, wa) contour, and we conclude that the cosmic shear is relatively insensitive to the binning methodology. We find that the information gain extracted on (w0, wa) for any 3x2pt component starts to saturate at 7-8 bins. Any marginal gains resulting from a greater number of bins is likely to be limited by additional uncertainties present in a real measurement, and the increasing demand for accuracy of the covariance matrix. Finally, we consider a 5% contamination from catastrophic photometric redshift outliers and find that, if these errors are not mitigated in the analysis, the bias induced in the 3x2pt signal for 10 equipopulated bins results in dark energy constraints that are inconsistent with the fiducial LambdaCDM cosmology at
Diffuse Supernova Neutrino Background and Neutrino Non-Radiative Decay: a Bayesian Perspective
No full textInternational audienceNeutrinos being massive could undergo non-radiative decay, a property for which the diffuse supernova neutrino background has a unique sensitivity. We extend previous analyses to explore our ability to disentangle predictions for the diffuse supernova neutrino background in presence or absence of neutrino non-radiative two-body decay. In a three-neutrino framework, we give predictions of the corresponding neutrino fluxes and the expected number of events in the Super-Kamiokande+Gadolinium, the Hyper-Kamiokande, the JUNO and the DUNE experiments. In our analysis, we employ supernova simulations from different groups and include current uncertainties from both the evolving core-collapse supernova rate and the fraction of failed supernovae. We perform the first Bayesian analysis to see our ability to disentangle the cases in presence and absence of neutrino decay. To this aim we combine the expected events in inverse beta-decay and the neutrino-argon detection channels. We also discuss neutrino-electron, neutrino-proton and of neutrino-oxygen scattering. Our investigation covers the different possible decay patterns for normal mass ordering, both strongly-hierarchical and quasi-degenerate as well as the inverted neutrino mass ordering
An Enigmatic PeVatron in an Area around HII Region G35.60.5
No full textInternational audienceIdentifying Galactic PeVatrons (PeV particle accelerators) from the ultra-high-energy (UHE, >100 TeV) -ray sources plays a crucial role in revealing the origin of Galactic cosmic rays. The UHE source 1LHAASO J1857+0203u is suggested to be associated with HESS J1858+020, which may be attributed to the possible PeVatron candidate supernova remnant (SNR) G35.60.4 or HII region G35.60.5. We perform detailed analysis on the very-high-energy and UHE -ray emissions towards this region with data from the Large High Altitude Air Shower Observatory (LHAASO). 1LHAASO J1857+0203u is detected with a significance of 11.6 above 100 TeV, indicating the presence of a PeVatron. It has an extension of with a power-law (PL) spectral index of 2.5 in 1-25 TeV and a point-like emission with a PL spectral index of 3.2 above 25 TeV. Using the archival CO and HI data, we identify some molecular and atomic clouds that may be associated with the TeV -ray emissions. Our modelling indicates that the TeV -ray emissions are unlikely to arise from the clouds illuminated by the protons that escaped from SNR G35.60.4. In the scenario that HII region G35.60.5 could accelerate particles to the UHE band, the observed GeV-TeV -ray emission could be well explained by a hadronic model with a PL spectral index of 2.0 and cutoff energy of 450 TeV. However, an evolved pulsar wind nebula origin cannot be ruled out
Prograde and retrograde stars in nuclear cluster mergers. Evolution of the supermassive black hole binary and the host galactic nucleus
No full textInternational audienceWe address the orbital distribution of stars in merging nuclear star clusters (NSCs) and the subsequent effects on supermassive black hole binary (SMBHB) evolution. We ran direct-summation -body simulations with different initial conditions to do a detailed study of the resulting NSC after their progenitors had merged. Our findings reveal that prograde stars form a flattened structure, while retrograde stars have a more spherical distribution. The axial ratios of the prograde component vary based on the presence and mass ratio of the SMBHs. The fraction of prograde and retrograde stars depends on the merger orbital properties and the SMBH mass ratio. The interactions of retrograde stars with the SMBHB affect the eccentricity and separation evolution of the binary. Our analysis reveals a strong correlation between the angular momentum and eccentricity of the SMBH binary. This relationship could serve as a means to infer information about the stellar dynamics surrounding the binary. We find that prograde orbits are particularly close to the binary of SMBHs, a promising fact regarding extreme mass ratio inspiral (EMRI) production. Moreover, prograde and retrograde stars have different kinematic structures, with the prograde stars typically rotating faster than the retrograde ones. The line-of-sight velocity and velocity dispersion, as well as the velocity anisotropy of each NSC, depend on the initial merger orbital properties and SMBH mass ratios. The prograde and retrograde stars always show different behaviours. The distribution of stellar orbits and the dynamical properties of each kinematic population can potentially be used as a way to tell the properties of the parent nuclei apart, and has an important impact on expected rates of EMRIs, which will be detected by future gravitational wave observatories such as the Laser Interferometer Space Antenna (LISA). [abridged
Modeling lunar response to gravitational waves using normal-mode approach and tidal forcing
No full textInternational audienceIn the light of the recent advances in lunar space missions a great interest into using Moon as a future environment for gravitational waves (GWs) detectors has been initiated. Moon offers a unique environment for such detectors due to constrained noise sources, since unlike Earth it does not have ocean and atmosphere. In this paper, we further explore the idea of using Moon as a giant resonator of GWs, a proposal that was first introduced by Weber in 1969. This idea is relaying on the theory how GWs interact with free masses and finally elastic solids, such as is a planet to some approximation. We start by carefully setting up General Relativity (physics) and elastic theory (geophysics) background to be able to derive analytically the coupling between GWs and elastic solids through associated equations of motion. Once the analytical solution is derived, we explore the parameter space this interaction depends on. This eventually provides us with the transfer function, which defines the frequency band of the interest. We show how this interaction robustly depends on the regolith structure by altering the initial lunar model and exploring different regolith models. Our results show that detection might be troublesome in the high frequency regime between 0.1 and 1 Hz, without beforehand constraining the regolith structure with geophysical methods. Finally, we discuss what are the implications of detecting these signals with the future GW detectors build on the Moon
EMRI_MC: A GPU-based code for Bayesian inference of EMRI waveforms
No full textInternational audienceWe describe a simple and efficient Python code to perform Bayesian forecasting for gravitational waves (GW) produced by Extreme-Mass-Ratio-Inspiral systems (EMRIs). The code runs on GPUs for an efficient parallelised computation of thousands of waveforms and sampling of the posterior through a Markov-Chain-Monte-Carlo (MCMC) algorithm. EMRI_MC generates EMRI waveforms based on the so--called kludge scheme, and propagates it to the observer accounting for cosmological effects in the observed waveform due to modified gravity/dark energy. Extending the code to more accurate schemes for the generation of the waveform is straightforward. Despite the known limitations of the kludge formalism, we believe that the code can provide a helpful resource for the community working on forecasts for interferometry missions in the milli-Hz scale, predominantly, the satellite-mission LISA
Three high resolution solar atlases of the 3000 Å - 9900 Å range
No full textWe present a set of useful high resolution atlases of the Sun in FITS format, originally produced by Delbouille et al (1972), Kurucz et al (1972) at disk centre, and Gandorfer (2000, 2002, 2005) close to the limb (µ = cosθ = 0.1). The ZIP file contains the FITS data (wavelength and intensity) together with derived sets of PNG spectral images of 100 Å bandwidth