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Explainable classification of astronomical uncertain time series
No full textInternational audienceExploring the expansion history of the universe, understanding its evolutionary stages, and predicting its future evolution are important goals in astrophysics. Today, machine learning tools are used to help achieving these goals by analyzing transient sources, which are modeled as uncertain time series. Although black-box methods achieve appreciable performance, existing interpretable time series methods failed to obtain acceptable performance for this type of data. Furthermore, data uncertainty is rarely taken into account in these methods. In this work, we propose an uncertaintyaware subsequence based model which achieves a classification comparable to that of state-of-the-art methods. Unlike conformal learning which estimates model uncertainty on predictions, our method takes data uncertainty as additional input. Moreover, our approach is explainable-by-design, giving domain experts the ability to inspect the model and explain its predictions. The explainability of the proposed method has also the potential to inspire new developments in theoretical astrophysics modeling by suggesting important subsequences which depict details of light curve shapes. The dataset, the source code of our experiment, and the results are made available on a public repository
Systematic studies of <math><mrow><mi>M</mi><mn>1</mn></mrow></math> photon strength functions with Skyrme-<math><mrow><mi>HFB</mi><mo>+</mo><mi>QRPA</mi></mrow></math> and the derived total dipole <math><mrow><mo>(</mo><mi>E</mi><mn>1</mn><mo>+</mo><mi>M</mi><mn>1</mn><mo>)</mo></mrow></math> resonance properties
No full textInternational audienceThe photon strength function (PSF) of nuclear dipole excitation is greatly important to different applications especially including nuclear astrophysics. However, for the ≈10000 nuclei over the whole nuclear chart, the total electric dipole (E1) and magnetic dipole (M1) PSF directly derived from large-scale calculation with microscopic theory is not available yet. In this paper, we perform a systematic study on the M1 PSF based on the microscopic Hartree-Fock-Bogoliubov plus quasiparticle random-phase approximation (HFB+QRPA) model used in our previous work of the E1 PSF. In particular, large-scale calculations of the spin-flip M1 strength distributions are performed in the framework of HFB+QRPA under the assumption of spherical symmetry using the BSk27 Skyrme effective interaction. The spin-flip M1 PSFs are obtained by folding the QRPA strength distributions with a Lorentz function that describes the damping of nuclear collective motion empirically. The scissors mode and the low-energy upbend contribution to the M1 PSFs are both added phenomenologically to the spin-flip component. The resulting BSk27+QRPA M1 PSF is shown to be in fairly good agreement with available experimental data. In addition, the comparison between our BSk27+QRPA M1 PSF and other theoretical results indicates that the present approach provides an efficient and reliable alternative to describe the M1 PSF for a large set of nuclei. When consistently considering both our previous E1 and the present M1 BSk27+QRPA PSFs, predictions reasonably reproduce multistep γ-ray cascade spectra, average radiative widths, and Maxwellian-averaged cross sections. A complete set of E1 and M1 PSFs are determined for ≈10000 nuclei with 8≤Z≤124 lying between the proton and the neutron drip lines and used to estimate astrophysical neutron capture rates that are found to be comparable to those obtained with the previous Gogny-HFB+QRPA predictions based on the D1M interaction
Impact of octupole vibrations on the fine structure of the ISGMR in Pb
No full textInternational audienceThe effects of the Phonon–Phonon Coupling (PPC) on the fine structure of the Isoscalar Giant Monopole Resonance (ISGMR) are studied in the quasiparticle-phonon model based on the Skyrme Energy Density Functional (EDF). Characteristic energy scales are extracted from the fine structure using continuous wavelet transforms. It is shown that an extension of the two-phonon space allowing for octupole phonons substantially enriches the spectrum of the energy scales. As an example, the ISGMR for the doubly magic [Formula: see text]Pb is discussed.</jats:p
Measurement of solar neutrino interaction rate below 3.49 MeV in Super-Kamiokande-IV
No full textInternational audienceSuper-Kamiokande has observed solar neutrino elastic scattering at recoil electron kinetic energies () as low as 3.49 MeV to study neutrino flavor conversion within the sun. At SK-observable energies, these conversions are dominated by the Mikheyev-Smirnov-Wolfenstein effect. An upturn in the electron neutrino survival probability in which vacuum neutrino oscillations become dominant is predicted to occur at lower energies, but radioactive background increases exponentially with decreasing energy. New machine learning approaches provide substantial background reduction below 3.49 MeV such that statistical extraction of solar neutrino interactions becomes feasible. This article presents an analysis of the solar neutrino interaction rate at < 3.49 MeV with the full SK-IV period, using data from a wideband intelligent trigger when available and with a boosted decision tree for event selection. A solar neutrino signal is observed between 2.99 MeV < < 3.49 MeV with significance and a data to unoscillated MC ratio of . This additional low energy data has a negligible effect on the intervals of the fits to the solar neutrino energy spectrum but has a noticeable effect on the best fit when using the exponential parameterization
Search for exotic Higgs boson decays H with in events with a semi-merged topology in proton-proton collisions at = 13 TeV
No full textInternational audienceA search for exotic Higgs boson decays H , with is presented, using events with a semi-merged topology. One of the hypothetical particles, , is assumed to decay promptly into a semi-merged diphoton system reconstructed as a single photon-like object, while the other decays into two resolved photons. The search is performed using proton-proton collision data collected by the CMS experiment at = 13 TeV, corresponding to an integrated luminosity of 138 fb. The data agree with the standard model background expectation. Upper limits are set on the product of the Higgs boson production cross section and the branching fraction, (pp H)(H 4), which range from 0.264 to 0.005 pb at 95% confidence level, for masses in the range 1 15 GeV. These limits are the most stringent to date in the 15 GeV range
Multiple Mellin-Barnes integrals with polygamma functions
No full textInternational audienceMellin-Barnes (MB) integrals appear in various branches of physics and mathematics and are, in particular, used as a standard tool for evaluating multi-loop, multi-scale Feynman integrals both analytically and numerically. Recent geometric approaches based on conic hulls and triangulations provide a systematic framework for computing multiple MB integrals in terms of multivariate series. These approaches have so far been limited to MB integrals whose integrands are ratios of products of Euler's gamma functions only. However, in Feynman integral calculus, MB integrals with polygamma functions naturally arise, for instance, after resolving singularities in the dimensional-regularisation parameter and expanding the MB integrand in powers of , as done by the public codes MB.m and MBresolve.m. In this paper, we extend the conic hull and triangulation methods to the computation of MB integrals having polygamma functions in their integrand. We show that the arguments of polygamma functions can be treated in a similar way to the arguments of gamma functions when applying the conic hull and triangulation techniques to identify poles that would contribute to different series solutions. However, since the singularity structure of the polygamma function is different from that of the gamma function, we propose two different ways to compute MB integrals involving polygamma functions, depending on whether the MB integral has straight or non-straight contours. We have implemented these algorithms in an updated version of the Mathematica package MBConicHulls.wl, which can be found at https://github.com/SumitBanikGit/MBConicHulls/, and we illustrate their use with a set of examples from Feynman integral calculus
Extending Weinberg's EFT: effective scalar-tensor theories up to sixth order
No full textInternational audienceWe present a systematic construction of the six-derivative effective scalar-tensor theories, extending the four-derivative framework previously developed by Steven Weinberg. The on-shell effective field theory comprises five parity-even and three parity-odd independent six-derivative scalar-tensor interactions, representing all inequivalent deformations consistent with general covariance. We further confirm this operator counting through an independent analysis using the scattering amplitude formalism in four-dimensional flat spacetime. The six-derivative Lagrangian constructed here provides the next-to-leading-order extension of scalar-tensor gravity, furnishing a robust framework for exploring quantum or stringy corrections, parity-violating interactions, and strong-curvature effects in cosmology, black hole physics and gravitational wave observations
Evaluating solid-state neutron detectors for measuring 14 MeV neutrons at high temperatures
No full textInternational audienceSilicon Carbide 4H Polytype (4H-SiC) and Diamond wide bandgap semiconductors are promising detector materials for fusion environments. Threshold energy nuclear reactions provide information on the energy of impinging fast neutrons and the combination of low intrinsic carrier concentration with high thermal conductivity makes these semiconductors suitable for high-temperature applications, especially for neutron monitoring in tritium production through ITER breeding blankets. While the carrier properties of SiC and Diamond offer interesting charge collection dynamics from room temperature up to 200 °C, the stability of their detection performance at high temperatures above 200 °C remains to be confirmed. To investigate this, we conducted a measurement campaign in a fast neutron field representative of fusion reactors at the GENESIS (Generator of Neutrons for Science and IrradiationS) research platform of LPSC (Laboratoire de Physique Subatomique et de Cosmologie) laboratory in Grenoble, France. Both 4H-SiC and Diamond sensors were irradiated with 14 MeV fast neutrons from a D-T neutron generator while encapsulated in a heating device, recording current signals from room temperature up to 500 °C. Using a direct measurement method of charge carrier collection dynamics as a function of applied bias voltage and temperature by pulse shape analysis provided information on velocity drift and collected charge. The results offer a first representative study of charge carrier mobility behavior with increasing temperature up to 500 °C. The stability of performance in terms of CCE (charge collection efficiency) has been demonstrated for SiC from room temperature up to 500 °C, while Diamond experiences a CCE drop of 60% between 200 °C and 300 °C
Electroweak precision tests for asymptotic Grand Unification models
No full textInternational audienceAsymptotic grand unification is an alternative framework to traditional quantitative unification, as the renormalisation flow leads towards an ultra-violet safe fixed point. Phenomenologically, 5-dimensional realisations permit new particles with masses as low as the TeV scale, well below the usual unification scale. We explore the impact of such models on electroweak precision observables, focusing on a minimal SU(5) template for concreteness. We show that current measurements are not sensitive to this class of models. Future colliders, such as CEPC and FCC-ee, can push the 95% limit on the Kaluza-Klein mass up to 2 and 4 TeV, respectively, beyond the direct reach of the LHC programme
Probing General Relativity on Cosmological Scales in the 2040s
No full textInternational audienceGeneral relativity is exquisitely tested in strong-field regimes, yet its validity on cosmological scales remains largely unexplored. Upcoming wide and deep large-scale structure surveys will access the ultra-large, linear scales where relativistic effects - Doppler terms, gravitational redshift, lensing magnification, and potential evolution - leave significant imprints in the clustering of galaxies. These signatures represent unique probes of spacetime that are inaccessible to standard Newtonian analyses but increasingly important as survey volumes grow. We outline the scientific potential of next-generation facilities, such as those envisioned within ESO's Expanding Horizons programme, to deliver the first robust measurements of relativistic effects in large-scale structure through multi-tracer power spectra and the single-tracer bispectrum of high-redshift Lyman-break galaxies. Detecting these contributions would open a new window on gravity, enabling precision tests of general relativity and its alternatives on cosmological scales in the 2040s