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Search for an eV-scale sterile neutrino with the first six detection units of KM3NeT/ORCA
No full textInternational audienceThe existence of an eV-scale sterile neutrino has been proposed to explain several anomalous experimental results obtained over the course of the past 25 years. The first search for such a sterile neutrino conducted with data from KM3NeT/ORCA -- a water Cherenkov neutrino telescope under construction at the bottom of the Mediterranean Sea -- is reported in this paper. GeV-scale atmospheric neutrino oscillations are measured by reconstructing the energy and arrival direction of up-going neutrinos that have traversed the Earth. This study is based on a data sample containing 5828 neutrino candidates collected with 6 detection units ( of the complete detector), corresponding to an exposure of 433 kton-years. From the expected effect of an eV-scale sterile neutrino on the first standard oscillation maximum, simultaneous constraints are put on the magnitude of the and mixing elements under the assumption eV. The results are compatible with the absence of mixing between active neutrinos and a sterile state, with and at a confidence level. Such constraints are compatible with the results reported by other long-baseline experiments, and indicate that with KM3NeT/ORCA it is possible to bring crucial contributions to sterile neutrino searches in the coming years
LiteBIRD Science Goals and Forecasts. -mode Anomalies
No full textInternational audienceVarious so-called anomalies have been found in both the WMAP and Planck cosmic microwave background (CMB) temperature data that exert a mild tension against the highly successful best-fit 6 parameter cosmological model, potentially providing hints of new physics to be explored. That these are real features on the sky is uncontested. However, given their modest significance, whether they are indicative of true departures from the standard cosmology or simply statistical excursions, due to a mildly unusual configuration of temperature anisotropies on the sky which we refer to as the "fluke hypothesis", cannot be addressed further without new information. No theoretical model of primordial perturbations has to date been constructed that can explain all of the temperature anomalies. Therefore, we focus in this paper on testing the fluke hypothesis, based on the partial correlation between the temperature and -mode CMB polarisation signal. In particular, we compare the properties of specific statistics in polarisation, built from unconstrained realisations of the CDM cosmological model as might be observed by the LiteBIRD satellite, with those determined from constrained simulations, where the part of the -mode anisotropy correlated with temperature is constrained by observations of the latter. Specifically, we use inpainted Planck 2018 SMICA temperature data to constrain the -mode realisations. Subsequent analysis makes use of masks defined to minimise the impact of the inpainting procedure on the -mode map statistics. We find that statistical assessments of the -mode data alone do not provide any evidence for or against the fluke hypothesis. However, tests based on cross-statistical measures determined from temperature and modes can allow this hypothesis to be rejected with a moderate level of probability
Dark Energy, and a Dark Fluid, from topology and a massless spinor
No full textInternational audienceUnder the existence of a massless spinor degrees of freedom in a spacetime with internal boundaries, such as black holes, we show that a topological mechanism naturally induces terms in the Einstein-Cartan gravitational action that can be interpreted as GR with dark energy and some dark fluid. This can alleviate the problems of dark energy, and perhaps of dark matter. The dark fluid term remains to be further analysed. The topological information is carried by a harmonic 1-form associated to the first co-holomology group of the spacetime, which induces a spacetime contortion acting on the horizontal bundle
Multi-epoch VLBI observations of the blazar 3C 66A: Spatial twisting and temporal oscillation of the parsec-scale jet
No full textInternational audiencePrevious VLBI kinematic studies of the blazar 3C 66A have unveiled complex jet kinematic behaviors. Using follow-up high-resolution VLBI observations and archival data, we investigate the morphology and the variations in orientation and core flux density of the 3C 66A jet to gain a deeper insights into its kinematic behavior and physical origins. We performed KVN and VERA array (KaVA) observations at 22/43 GHz over three epochs in 2014 and collected 109 sets of Very Long Baseline Array (VLBA) archival data at 43 GHz between 1996 - 2025. We imaged the parsec-scale jet and parameterized it using circular Gaussian fittings to the UV visibilities. Finally, we derived the inner jet PA and the core flux densities for the VLBA data. The jet presents a twisted morphology in the KaVA maps. The PA of the fitted Gaussian components is in the range between 170 deg and 195 deg. Our kinematic analysis using the VLBA data indicates that the PA oscillates with an amplitude of 7.77 pm 0.79 deg and a period of 10.94 pm 0.22 years, presented for the first time in this work. This oscillation is topped by a continuous clockwise shift of the PA by -0.83 pm 0.07 deg/year. We also identified a strong core flux variability with possible periodicity and a 2 sigma correlation between the core flux density and the inner jet PA change. We discuss possible physical models that could explain the observed features for this object; in particular, a supermassive black hole binary (SMBHB) system, Lense Thirring (LT) effect, and jet or disk instabilities. The oscillation and continuous shift of the PA and the possible radio flux periodicity, together with the optical flux periodicity of approximately 2 years that had previously been confirmed in several independent studies, favor a jet precession scenario driven by orbital motion and disk-orbit misalignment in a SMBHB system
Black Hole Spectroscopy and Tests of General Relativity with GW250114
No full textInternational audienceThe binary black hole signal GW250114, the loudest gravitational wave detected to date, offers a unique opportunity to test Einstein’s general relativity (GR) in the high-velocity, strong-gravity regime and probe whether the remnant conforms to the Kerr metric. Upon perturbation, black holes emit a spectrum of damped sinusoids with specific, complex frequencies. Our analysis of the postmerger signal shows that at least two quasinormal modes are required to explain the data, with the most damped remaining statistically significant for about one cycle. We probe the remnant’s Kerr nature by constraining the spectroscopic pattern of the dominant quadrupolar (ℓ=m=2) mode and its first overtone to match the Kerr prediction to tens of percent at multiple postpeak times. The measured mode amplitudes and phases agree with a numerical-relativity simulation having parameters close to GW250114. By fitting a parametrized waveform that incorporates the full inspiral-merger-ringdown sequence, we constrain the fundamental (ℓ=m=4) mode to tens of percent and bound the quadrupolar frequency to within a few percent of the GR prediction. We perform a suite of tests—spanning inspiral, merger, and ringdown—finding constraints that are comparable to, and in some cases 2–3 times more stringent than those obtained by combining dozens of events in the fourth Gravitational-Wave Transient Catalog. These results constitute the most stringent single-event verification of GR and the Kerr nature of black holes to date, and outline the power of black-hole spectroscopy for future gravitational-wave observations
Deep Search for Joint Sources of Gravitational Waves and High-Energy Neutrinos with IceCube During the Third Observing Run of LIGO and Virgo
No full textInternational audienceThe discovery of joint sources of high-energy neutrinos and gravitational waves has been a primary target for the LIGO, Virgo, KAGRA, and IceCube observatories. The joint detection of high-energy neutrinos and gravitational waves would provide insight into cosmic processes, from the dynamics of compact object mergers and stellar collapses to the mechanisms driving relativistic outflows. The joint detection of multiple cosmic messengers can also elevate the significance of the common observation even when some or all of the constituent messengers are sub-threshold, i.e. not significant enough to declare their detection individually. Using data from the LIGO, Virgo, and IceCube observatories, including sub-threshold events, we searched for common sources of gravitational waves and high-energy neutrinos during the third observing run of Advanced LIGO and Advanced Virgo detectors. Our search did not identify significant joint sources. We derive constraints on the rate densities of joint sources. Our results constrain the isotropic neutrino emission from gravitational-wave sources for very high values of the total energy emitted in neutrinos (> erg)
Reconstruction of atmospheric neutrinos in DUNE's horizontal-drift far-detector module
No full textInternational audienceThis paper reports on the capabilities in reconstructing and identifying atmospheric neutrino interactions in one of the Deep Underground Neutrino Experiment's (DUNE) far detector modules, a liquid argon time projection chamber (LArTPC) with horizontal drift (FD-HD) of ionization electrons. The reconstruction is based upon the workflow developed for DUNE's long-baseline oscillation analysis, with some necessary machine-learning models' retraining and the addition of features relevant only to atmospheric neutrinos such as the neutrino direction reconstruction. Where relevant, the impact of the detection of the charged particles of the hadronic system is emphasized, and comparisons are carried out between the case when lepton-only information is considered in the reconstruction (as is the case for many neutrino oscillation experiments), versus when all particles identified in the LArTPC were included. Three neutrino direction reconstruction methods have been developed and studied for the atmospheric analyses: using lepton-only information, using all reconstructed particles, and using only correlations from reconstructed hits. The results indicate that incorporating more than just lepton information significantly improves the resolution of both neutrino direction and energy reconstruction. The angle reconstruction algorithms developed in this work result in no strong dependence on particle direction for reconstruction efficiencies or neutrino flavor identification. This comprehensive review of the reconstruction of atmospheric neutrinos in DUNE's FD-HD LArTPC is the first step towards developing a first neutrino oscillation sensitivity analysis, which will ready DUNE for its first measurements
Quasinormal modes of rotating black holes beyond general relativity in the WKB approximation
No full textInternational audienceExploring gravitational theories beyond general relativity (GR) with black hole (BH) spectroscopy requires accurate and flexible methods for computing their quasinormal mode (QNM) spectrum. A popular method of choice is the higher-order Wentzel-Kramers-Brillouin (WKB) approximation, mostly applied to nonrotating BHs. While previous studies demonstrated that the higher-order WKB method can also be used for Kerr BHs in GR, there has been little work on rotating BHs in modified theories of gravity. In this work, we revive the idea by extending WKB calculations of the Kerr QNM spectrum to higher order and assessing its accuracy against continued-fraction tabulated data. We then apply the WKB approximation beyond GR, comparing it against both linearized and continued fraction calculations in the parametrized beyond-Teukolsky formalism and in higher-derivative gravity (HDG) theories. We find that the frequencies computed by the WKB method in theories beyond GR have better accuracy than the measurement errors for GW250114, the event with the highest ringdown signal-to-noise ratio observed to date
The Simons Observatory: forecasted constraints on primordial gravitational waves with the expanded array of Small Aperture Telescopes
No full textInternational audienceWe present updated forecasts for the scientific performance of the degree-scale (0.5 deg FWHM at 93 GHz), deep-field survey to be conducted by the Simons Observatory (SO). By 2027, the SO Small Aperture Telescope (SAT) complement will be doubled from three to six telescopes, including a doubling of the detector count in the 93 GHz and 145 GHz channels to 48,160 detectors. Combined with a planned extension of the survey duration to 2035, this expansion will significantly enhance SO's search for a -mode signal in the polarisation of the cosmic microwave background, a potential signature of gravitational waves produced in the very early Universe. Assuming a noise model with knee multipole and a moderately complex model for Galactic foregrounds, we forecast a (or 68% confidence level) constraint on the tensor-to-scalar ratio of , assuming no primordial -modes are present. This forecast assumes that 70% of the -mode lensing signal can ultimately be removed using high resolution observations from the SO Large Aperture Telescope (LAT) and overlapping large-scale structure surveys. For more optimistic assumptions regarding foregrounds and noise, and assuming the same level of delensing, this forecast constraint improves to . These forecasts represent a major improvement in SO's constraining power, being a factor of around 2.5 times better than what could be achieved with the originally planned campaign, which assumed the existing three SATs would conduct a five-year survey
Selection of Chemical Adsorbents and Operating Conditions for the Injection Traps of the Gas Chromatograph on Board the Dragonfly Mass Spectrometer
No full textInternational audienceThe Dragonfly mission is set to explore Titan’s surface in the mid-2030s. This relocatable lander is equipped with the Dragonfly Mass Spectrometer (DraMS) instrument. One of DraMS functioning mode is gas chromatography−mass spectrometry, to identify organic compounds in solid samples. DraMS-GC includes two independent chemical injection traps to focus the molecules released from the sample. Initially, Tenax TA was planned to be the adsorbent in the injection traps because of its heritage in previous space probes. However, Tenax TA has shown some decomposition products that challenge the identification of the molecules indigenous to the sample. In this work, the performance of another adsorbent powder, Carbotrap C, was compared to Tenax TA. Performance was evaluated in DraMS-like desorption conditions by comparing the recovery yield after adsorption and desorption of a set of 53 organic compounds of interest to Titan. Recovery with Carbotrap C was either similar or better than with Tenax TA for 79% of compounds. This recovery yield was further improved by increasing the desorption temperature. DraMS low desorption flow rate appears to be the most limiting parameter for recovery. Desorption from both Tenax TA and Carbotrap C led to partial but comparable racemization for three of the four amino acids that were enantiomerically resolved. Together, these results led to the integration of Carbotrap C in one of the DraMS injection traps