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Gwenhaël de Wasseige

Publications and source records attributed to Gwenhaël de Wasseige.

At least 19 recordsLinked to original sources

SPORE: An Event-Level Sampling Pipeline for Multi-Telescope Neutrino Astronomy

We present an open-source Python package for simulating neutrino events from astrophysical point and extended sources using tabulated instrument response functions (IRFs). The package encodes three detector response components - effective area, point spread function, and energy resolution - in a selection-agnostic HDF5 format, which can represent a neutrino telescope whose response is supplied in that form, whether from a public release or a private study. Sampling algorithms cover point sources (inverse-CDF with Poisson or fixed-count modes), extended sky distributions (hierarchical inverse-CDF sampling, including full RA- and declination-dependent flux maps), and multi-detector joint analyses. We validate the framework via a round-trip consistency test using the publicly available IceCube 10-year tracks data release: the released IRFs are ingested into the package and used to generate a synthetic event set, whose declination distribution reproduces the observed one to 10-15% across the northern sky. The reconstructed-energy distribution agrees to within about a third over the bulk of the sample but exceeds the data by up to a factor of three below 600 GeV, a discrepancy we trace to the coarse true-energy binning of the public smearing matrix rather than to the sampling: an independent forward fold of the same IRFs reproduces it. We further compare against the IceCube HESE 7.5-year public data release: the sampled deposited-energy spectrum tracks the published best-fit expectation, and the observed data fall within the goodness-of-fit distribution built from 1,000 sampled pseudo-experiments, though on its well-fitting side, as expected for an expectation that was itself fit to those data.

astro-ph.IM↗

Prospective Sensitivity to Solar Dark Matter using the IceCube Upgrade

While astrophysical observations imply that 85% of the matter content is unaccounted for, the nature of this dark matter (DM) component remains unknown. Weakly Interacting Massive Particles (WIMPs) - DM particles that interact at or below the weak interaction scale - could naturally explain this missing matter. These interactions with the Standard Model (SM) allow them to be gravitationally captured in celestial bodies like the Sun. Trapped DM in the solar core could subsequently annihilate, producing stable SM particles, of which only neutrinos can escape the Sun's dense interior. Therefore, an excess of neutrinos originating from the direction of the Sun would serve as evidence of DM. The IceCube Upgrade, a dense infill of the IceCube Neutrino Observatory, will lower the energy threshold and improve sensitivity in the range from 1 to 500 GeV, thereby enhancing IceCube's ability to detect GeV-scale DM. In this contribution, I present projections of the IceCube Upgrade's sensitivity to the DM-proton scattering cross section for DM masses between 3 GeV and 500 GeV. These sensitivities position IceCube as the most sensitive indirect detection experiment for DM in the mass range from 3 GeV to 10 TeV.

astro-ph.HE↗

Probing neutrino emission at GeV energies from compact binary mergers detected during O1-O4a with the IceCube Neutrino Observatory

Compact binary mergers, detected in gravitational waves since 2015, are candidate sources for astrophysical neutrinos in the GeV regime from proton-proton and proton-neutron collisions. This contribution presents the results of the search for such a signal using mergers detected during the fourth observing run of the LIGO, Virgo, and KAGRA interferometers. We use the dense infill array at the center of the IceCube detector, IceCube-DeepCore, to select neutrino candidates in the 0.5-5 GeV energy range. The search for a statistically significant excess associated with an astrophysical signal is performed in a $\pm$ 500 s window around the gravitational wave detection time. We do not observe any statistically significant excess in the neutrino data, and set upper limits on the neutrino emission from these objects. Additionally, we search for subpopulations of neutrino-emitting sources, including merger events detected in previous observing runs; no significant signal has been identified yet.

astro-ph.HE↗

Prospects for sub-GeV astrophysical neutrino detection with IceCube

The IceCube Neutrino Observatory is currently the largest and most sensitive detector for astrophysical neutrinos and has pioneered the field of high-energy neutrino astronomy. Despite being designed with the primary goal of identifying astrophysical TeV neutrinos and their corresponding sources, recent studies, utilising the DeepCore subdetector, have shown IceCube's proficiency in being sensitive to astrophysical neutrinos at GeV energies. Currently, there is a gap in sensitivity between the supernova detection system at MeV energies and the lowest-energy triggering events around 1 GeV. In this contribution, we present the ongoing efforts to cover this gap and increase the sensitivity of IceCube to sub-GeV astrophysical neutrinos. Despite high background rates, we show how the complimentary use of manifold and supervised machine learning can make IceCube sensitive to neutrinos from transient sources down to energies of 100 MeV.

astro-ph.HE↗

IceCube searches for GeV neutrino counterparts associated with high-energy starting events

The origin of the astrophysical neutrino flux observed by IceCube is largely unknown. To help decipher its astrophysical origin, we propose an IceCube analysis that conducts follow-up searches for GeV neutrinos associated with neutrino events above 60 TeV, which are known to have a high probability to be of astrophysical origin. It could not only identify a new component of the astrophysical neutrino flux, but also characterize how its spectrum extrapolates from GeV to PeV energies. This would in turn give valuable insights into the internal processes of neutrino sources. Astrophysical transients, such as collapsars, have been proposed as sources of time-correlated GeV- and high-energy neutrinos. Conducting this search in such short time scales allows for a substantial reduction in the dominant background rate for GeV neutrino candidate events. We introduce the statistical method and sensitivity of this search as well as dedicated data quality checks. None of the searches yield statistically significant results, and we present the first limits on GeV neutrino emission associated to VHE neutrino events at short time scales.

astro-ph.HE↗

Searching for sub-populations within the gamma-ray solar flares catalog: a graph-based clustering analysis

Solar flares are highly energetic events that happen in the solar atmosphere. They are mostly observed as X-ray or gamma-ray bursts located on the Sun's surface. While they are known to be sites of particle acceleration, the acceleration process(es) responsible for the observed fluxes remain unsure. The diversity in shape and duration of the gamma-ray fluxes suggests the existence of distinct phases of hadronic acceleration. Moreover, different acceleration processes could explain the differences observed among flares. In this work we search for the evidence of sub-populations within the catalog of gamma-ray solar flares observed by Fermi-LAT. We aim at grouping flares with similar physical properties to be able to probe theoretical models for neutrino production within different classes of flares. We use measurements of the X-ray and gamma-ray fluxes, as well as CMEs and SEPs, to cluster the events using a graph-based algorithm. Furthermore, we investigate the most representative features that characterise the identified sub-populations to allow for qualitative analysis and model development.

astro-ph.SR↗

The classification and categorisation of Gamma-Ray Bursts with machine learning techniques for neutrino detection

While Gamma-Ray Burst (GRBs) are clear and distinct observed events, every individual GRB is unique. In fact, GRBs are known for their variable behaviour, and BATSE was already able to discover two categories of GRB from the T90 distribution; the short and long GRBs. These two categories match up with the expected two types of GRB progenitors. Nowadays, more features have been found to be able to further distinguish them, such as the hardness ratio or the presence of supernovae. However, that does not mean that it is by any means simple to categorise individual GRBs. Furthermore, more GRB categories have been theorised as well, such as low-luminosity or X-ray-rich GRBs. These different types of GRBs also could indicate a different neutrino spectrum, with different types of GRBs more likely to emit higher amounts of neutrinos. We present an ongoing effort to use machine learning to categorise and classify GRBs, searching for subpopulations that could yield a larger neutrino flux. We specifically use unsupervised learning, as it allows hidden patterns and correlations to come to light. With the help of features such as the T90, hardness, fluence, SNR, spectral index and even the full light curve and spectra, different structures and categories of Gamma-Ray bursts can be found.

astro-ph.HE↗

Identification of time-correlated neutrino clusters in populations of astrophysical transient sources

The detection of astrophysical neutrinos from transient sources can help to understand the origin of the neutrino diffuse flux and to constrain the underlying production mechanisms. In particular, proton-neutron collisions may produce GeV neutrinos. However, at these energies, neutrino data from large water Cherenkov telescopes, like KM3NeT and IceCube, are dominated by the well-known atmospheric neutrino flux. It is then necessary to identify a sub-dominant component due to an astrophysical emission based on time correlation across messengers. The contribution covers several methods to search for such a signal in short time windows centered on observed transient sources, including a novel approach based on the distribution of time differences. Their performance is compared in the context of subpopulations of astrophysical sources that may show prompt or delayed neutrino emissions. The outlook for the usage of such techniques in actual analyses is also presented.

astro-ph.IM↗

Probing neutrino emission at GeV energies from astrophysical transient events with the IceCube Neutrino Observatory

Astrophysical transient events like Gamma Ray Bursts (GRBs) have always been promising candidates for multi-messenger astronomy, with electromagnetic and gravitational wave signals having already been observed in GRBs such as GRB 170817A. The neutrino signatures of these bursts have been long-awaited as well, with many models predicting different spectra. Most of these searches have been in the hundreds of GeV to PeV range. However, as different models indicate a possible lower energy neutrino signal, we intend to expand this search to the lowest limits of IceCube (0.5-5 GeV) as well. With the plan to look at more transient events, we present the result of the first IceCube search for < 5 GeV astrophysical neutrinos emitted from a GRB, for GRB 221009A; the brightest GRB ever observed. Furthermore, we present plans to improve the observations of < 5 GeV neutrinos in IceCube, with which we plan to probe more transient events in the future. These improvements include the addition of direction reconstruction at these energies, and optimization of the noise rejection. With these improvements, GRB 221009A is just the start of the low-energy neutrino search from transient events with IceCube.

astro-ph.HE↗

First results of low-energy neutrino follow-ups of Run O4 compact binary mergers with the IceCube Neutrino Observatory

We present the results of searches for astrophysical neutrinos of few GeV energy from compact binary mergers detected during the first months of the fourth observing run of the LIGO, Virgo, and KAGRA interferometers. We describe our method, based on a selection of $0.5-5$ GeV neutrino events in IceCube, where we search for a statistically significant increase in the number of low-energy candidate events detected around the compact binary merger time. With these results, we constrain neutrino-emitting source populations. Finally, we compare our results with constraints set by neutrino searches at $> 10$ GeV energies and describe the complementarity of these low- and high-energy searches.

astro-ph.HE↗

KM3NeT sensitivity to low energy astrophysical neutrinos

KM3NeT, a new generation of neutrino telescope, is currently being deployed in the Mediterranean Sea. While its two sites, ORCA and ARCA, were respectively designed for the determination of neutrino mass hierarchy and high-energy neutrino astronomy, this contribution presents a study of the detection potential of KM3NeT in the MeV-GeV energy range. At these low energies, the data rate is dominated by low-energy atmospheric muons and environmental noise due to bioluminescence and K-40 decay. The goal of this study is to characterize the environmental noise in order to optimize the selection of low-energy neutrino interactions and increase the sensitivity of KM3NeT to transient astrophysical phenomena, such as close-by core-collapse Supernovae, solar flares, and extragalactic transients. In this contribution, we will study how using data science tools might improve the sensitivity of KM3NeT in these low-energy neutrino searches. We will first introduce the data sets and the different variables used to characterize KM3NeT's response to the environmental noise. We will then compare the efficiency of various tools in identifying different components in the environmental noise and in disentangling low-energy neutrino interactions from the background events. We will conclude with the implication of low-energy neutrinos for future astrophysical transient searches.

astro-ph.HE↗

Multi-detector approach to enhance the sensitivity of neutrino telescopes to low-energy astrophysical sources

While large neutrino telescopes have so far mainly focused on the detection of TeV-PeV astrophysical neutrinos, several efforts are ongoing to extend the sensitivity down to the GeV level for transient sources. Only a handful of neutrino searches have been carried out at the moment leaving the signature of astrophysical transients poorly known in this energy range. In this contribution, we discuss the motivations for high-energy neutrino telescopes to explore the GeV energy range and summarize the current limitations of detectors, such as IceCube and KM3NeT. We then present and compare different approaches for multi-detector analyses that may enhance the sensitivity to a transient GeV neutrino flux.

astro-ph.HE↗

Event reconstruction for KM3NeT/ORCA using convolutional neural networks

The KM3NeT research infrastructure is currently under construction at two locations in the Mediterranean Sea. The KM3NeT/ORCA water-Cherenkov neutrino detector off the French coast will instrument several megatons of seawater with photosensors. Its main objective is the determination of the neutrino mass ordering. This work aims at demonstrating the general applicability of deep convolutional neural networks to neutrino telescopes, using simulated datasets for the KM3NeT/ORCA detector as an example. To this end, the networks are employed to achieve reconstruction and classification tasks that constitute an alternative to the analysis pipeline presented for KM3NeT/ORCA in the KM3NeT Letter of Intent. They are used to infer event reconstruction estimates for the energy, the direction, and the interaction point of incident neutrinos. The spatial distribution of Cherenkov light generated by charged particles induced in neutrino interactions is classified as shower- or track-like, and the main background processes associated with the detection of atmospheric neutrinos are recognized. Performance comparisons to machine-learning classification and maximum-likelihood reconstruction algorithms previously developed for KM3NeT/ORCA are provided. It is shown that this application of deep convolutional neural networks to simulated datasets for a large-volume neutrino telescope yields competitive reconstruction results and performance improvements with respect to classical approaches.

astro-ph.IM↗

gSeaGen: the KM3NeT GENIE-based code for neutrino telescopes

The gSeaGen code is a GENIE-based application developed to efficiently generate high statistics samples of events, induced by neutrino interactions, detectable in a neutrino telescope. The gSeaGen code is able to generate events induced by all neutrino flavours, considering topological differences between track-type and shower-like events. Neutrino interactions are simulated taking into account the density and the composition of the media surrounding the detector. The main features of gSeaGen are presented together with some examples of its application within the KM3NeT project.

astro-ph.IM↗

High-Energy Neutrino Astronomy: Current Status and Prospects

In the last decade, neutrino astronomy has taken off with two major breakthroughs, the first observation of high-energy astrophysical neutrinos in 2013 and the first evidence for gamma-rays and neutrinos from a single object published in summer 2018. In this talk, we will review these important milestones as well as the other noteworthy achievements reached by the community. We will emphasize the important role of neutrino searches in the multi-messenger era and describe the current efforts carried out in the large neutrino telescope community. We will conclude with an outlook for the coming decade.

astro-ph.HE↗

Probing neutrino emission at GeV energies from compact binary mergers with IceCube

The advent of Multi-Messenger Astronomy has allowed for new types of source searches within the neutrino community. We present the results of the first search for GeV astrophysical neutrinos emitted from Compact Binary Mergers, i.e. binary black hole or binary neutron star mergers, detected by the LIGO and Virgo interferometers. We introduce a new approach that lowers the energy threshold of IceCube from roughly 10 GeV to <1 GeV. This method uses an innovative event selection of GeV neutrino events in IceCube and searches for a statistically significant increase in the amount of GeV-like events detected around the Compact Binary Merger time. We compare our results with constraints set by high-energy neutrino searches, and describe the complementarity of these low and high-energy searches.

astro-ph.HE↗

First search for GeV neutrinos from bright gamma-ray solar flares using the IceCube Neutrino Observatory

In response to a reported increase in the total neutrino flux in the Homestake experiment in coincidence with solar flares at the end of the eighties, solar neutrino detectors have searched for solar flare signals. Solar flares convert magnetic energy into thermal energy of plasma and kinetic energy of charged particles such as protons. As a consequence of magnetic reconnection, protons are injected downwards from the coronal acceleration region and can interact with dense plasma in the lower solar atmosphere, producing mesons that will subsequently decay into gamma rays and neutrinos at O(MeV-GeV) energies. The main motivation to search for solar flare neutrinos comes from their hadronic origin. As inherent products of high-energy proton collisions with the chromosphere, they are a direct probe of the proton accelerated towards the chromosphere. Using a multi-messenger approach, it is therefore possible to constrain the proton acceleration taking place in the solar flares, including the spectral index of the accelerated flux and its shape. We present the results of the first search for GeV neutrinos emitted during solar flares carried out with the IceCube Neutrino Observatory. We present a new approach which allows us to strongly lower the energy threshold of IceCube, originally designed to detect 10 GeV - PeV neutrinos. We compare the results with theoretical estimates of the corresponding flux.

astro-ph.HE↗

Synergy between Art and Science: Collaboration at the South Pole

We present the result of a cross-disciplinary collaboration between Prof. Donald Fortescue of the California College of the Arts in San Francisco and the Dr. Gwenhael de Wasseige of the IceCube Collaboration. The work presented was initiated during Fortescue's US National Science Foundation funded Antarctic Artists and Writers Fellowship at the South Pole in the austral summer of 2016/17. One outcome of this collaboration is the video work Axis Mundi - a timelapse movie captured during 24 hours at the South Pole, combined with a simultaneous sampling of IceCube data transduced into sound. Axis Mundi captures the rotation of the Earth in space, the transient motions of the atmosphere, and the passage of subatomic particles through the polar ice, to provide a means for us to physically engage with these phenomena. We detail how both the timelapse and the transduction of atmospheric muon data have been realized and discuss the benefits of such a collaboration.

physics.pop-ph↗