arXiv subjects

Justin Vandenbroucke

Publications and source records attributed to Justin Vandenbroucke.

At least 37 records · Page 2Linked to original sources

arXiv2021

TauRunner: A Public Python Program to Propagate Neutral and Charged Leptons

In the past decade IceCube's observations have revealed a flux of astrophysical neutrinos extending to $10^{7}~\rm{GeV}$. The forthcoming generation of neutrino observatories promises to grant further insight into the high-energy neutrino sky, with sensitivity reaching energies up to $10^{12}~\rm{GeV}$. At such high energies, a new set of effects becomes relevant, which was not accounted for in the last generation of neutrino propagation software. Thus, it is important to develop new simulations which efficiently and accurately model lepton behavior at this scale. We present TauRunner a PYTHON-based package that propagates neutral and charged leptons. TauRunner supports propagation between $10~\rm{GeV}$ and $10^{12}~\rm{GeV}$. The package accounts for all relevant secondary neutrinos produced in charged-current tau neutrino interactions. Additionally, tau energy losses of taus produced in neutrino interactions is taken into account, and treated stochastically. Finally, TauRunner is broadly adaptable to divers experimental setups, allowing for user-specified trajectories and propagation media, neutrino cross sections, and initial spectra.

hep-ph↗

arXiv2021

Searching for Neutrino Transients Below 1 TeV with IceCube

Recent observations of GeV gamma-rays from novae have led to a paradigm shift in the understanding of these objects. While it is now believed that shocks contribute significantly to the energy budget of novae, it is still unknown if the emission is hadronic or leptonic in origin. Neutrinos could hold the key to definitively differentiating between these two scenarios, though the energies of such particles would be much lower than are typically targeted with neutrino telescopes. IceCube's densely instrumented DeepCore sub-array provides the ability to reduce the threshold for observation from 1 TeV down to approximately 10 GeV. We will discuss recent measurements in this low energy regime, details of a new sub-TeV selection, and prospects for future searches for transient neutrino emission.

astro-ph.HE↗

arXiv2021

Multi-messenger searches via IceCube's high-energy neutrinos and gravitational-wave detections of LIGO/Virgo

We summarize initial results for high-energy neutrino counterpart searches coinciding with gravitational-wave events in LIGO/Virgo's GWTC-2 catalog using IceCube's neutrino triggers. We did not find any statistically significant high-energy neutrino counterpart and derived upper limits on the time-integrated neutrino emission on Earth as well as the isotropic equivalent energy emitted in high-energy neutrinos for each event.

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arXiv2021

Testing the AGN Radio and Neutrino correlation using the MOJAVE catalog and 10 years of IceCube Data

On 22 September 2017, IceCube reported a high-energy neutrino event which was found to be coincident with a flaring blazar, TXS 0506+056. This multi-messenger observation hinted at blazars contributing to the observed high-energy astrophysical neutrinos and raised a need for extensive correlation studies. Recent work shows that the internal absorption of gamma rays, and their interactions intrinsic to the source and with the extragalactic background, will cause a lack of energetic gamma-ray and neutrino correlation while hinting towards a correlation between neutrinos and lower photon energy observations in the X-ray and radio bands. Studies based on published IceCube alerts and radio observations report a possible radio-neutrino correlation in both gamma-ray bright and gamma-ray dim active galactic nuclei (AGN). However, they have marginal statistical significance due to limited available data. We present a correlation analysis between 15 GHz radio observations of AGN reported in the MOJAVE XV catalog and 10 years of IceCube detector data and discuss the results derived from a time-averaged stacking analysis.

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arXiv2019

Observing EeV neutrinos through the Earth: GZK and the anomalous ANITA events

Tau neutrinos are unique cosmic messengers, especially at extreme energies. When they undergo a charged-current interaction, the short lifetime of the produced tau gives rise to secondary tau neutrinos that carry a significant fraction of the primary neutrino energy. This effect, known as tau neutrino regeneration, has not been applied to its full potential in current generation neutrino experiments. In this work, we present an updated calculation of tau neutrino regeneration, and explore its implications for two scenarios: the recent anomalous ANITA events and the cosmogenic neutrino flux. For the former, we investigate the idea of localized emission and find that the maximum secondary neutrino flux allowed by IceCube measurements implies a primary flux that is incompatible with the ANITA observation, regardless of the assumed source energy spectrum. For the latter, we study the prospect of detecting the cosmogenic neutrino flux of regenerated PeV neutrinos with current and next generation neutrino detectors.

hep-ph↗

arXiv2019

IceCube as a Multi-messenger Follow-up Observatory for Astrophysical Transients

The recent association between IC-170922A and the blazar TXS0506+056 highlights the importance of real-time observations for identifying possible astrophysical neutrino sources. Thanks to its near-100\% duty cycle, 4$π$ steradian field of view, and excellent sensitivity over many decades of energy, IceCube is well suited both to generate alerts for follow-up by other instruments and to rapidly follow up alerts generated by other instruments. Detection of neutrinos in coincidence with transient astrophysical phenomena serves as a smoking gun for hadronic processes and supplies essential information about the identities and mechanisms of cosmic-ray accelerators. In 2016, the IceCube Neutrino Observatory established a pipeline to rapidly search for neutrinos from astrophysical transients on timescales ranging from a fraction of a second to multiple weeks. Since then, 67 dedicated analyses have been performed searching for associations between IceCube neutrinos and astrophysical transients reported by radio, optical, X-ray, and gamma-ray instruments in addition to searching for lower energy neutrino signals in association with IceCube's own high-energy alerts. We present the event selection, maximum likelihood analysis method, and sensitivity of the IceCube real-time pipeline. We also summarize the results of all follow-up analyses to date.

astro-ph.HE↗

arXiv2019

Searches for neutrinos from fast radio bursts with IceCube

Although IceCube has discovered a diffuse astrophysical neutrino flux, the underlying sources of these neutrinos remain unknown. Transient astrophysical objects, such as fast radio bursts (FRBs), could explain a large percentage of the measured flux. We present the analysis techniques of IceCube searches for MeV to TeV neutrinos from FRBs. As no significant correlation between IceCube neutrinos and FRBs has been found, we present the first limit on MeV neutrino emission from FRBs and the most constraining limits for neutrinos with GeV to TeV energies. We also describe the prospects for future IceCube neutrino searches coinciding with FRB detections from next generation radio interferometers.

astro-ph.HE↗

arXiv2019

A Search for IceCube Neutrinos from the First 33 Detected Gravitational Wave Events

The discoveries of high-energy astrophysical neutrinos by IceCube in 2013 and of gravitational waves by LIGO in 2015 have enabled a new era of multi-messenger astronomy. Gravitational waves can identify the merging of compact objects such as neutron stars and black holes. These compact mergers, especially neutron star mergers, are potential neutrino sources. We present an analysis searching for neutrinos from gravitational wave sources reported by the LIGO Virgo Collaboration (LVC). We use a dedicated transient likelihood analysis combining IceCube events with source localizations provided by LVC as spatial priors. We report results for all gravitational wave events from the O1, O2, and O3 observing runs.

astro-ph.HE↗

arXiv2019

A search for IceCube events in the direction of ANITA neutrino candidates

The Antarctic Impulsive Transient Antenna (ANITA) collaboration has reported a total of three neutrino candidates from the experiment's first three flights. One of these was the lone candidate in a search for Askaryan radio emission, and the others can be interpreted as tau-neutrinos, with important caveats. Among a variety of explanations for these events, they may be produced by astrophysical transients with various characteristic timescales. We test the hypothesis that these events are astrophysical in origin by searching for IceCube counterparts. Using seven years of IceCube data from 2011 through 2018, we search for neutrino point sources using integrated, triggered, and untriggered approaches, and account for the substantial uncertainty in the directional reconstruction of the ANITA events. Due to its large livetime and effective area over many orders of magnitude in energy, IceCube is well suited to test the astrophysical origin of the ANITA events.

astro-ph.HE↗

arXiv2018

Particle Identification In Camera Image Sensors Using Computer Vision

We present a deep learning, computer vision algorithm constructed for the purposes of identifying and classifying charged particles in camera image sensors. We apply our algorithm to data collected by the Distributed Electronic Cosmic-ray Observatory (DECO), a global network of smartphones that monitors camera image sensors for the signatures of cosmic rays and other energetic particles, such as those produced by radioactive decays. The algorithm, whose core component is a convolutional neural network, achieves classification performance comparable to human quality across four distinct DECO event topologies. We apply our model to the entire DECO data set and determine a selection that achieves $\ge90\%$ purity for all event types. In particular, we estimate a purity of $95\%$ when applied to cosmic-ray muons. The automated classification is run on the public DECO data set in real time in order to provide classified particle interaction images to users of the app and other interested members of the public.

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arXiv2017

A Search for Cosmic-ray Proton Anisotropy with the Fermi Large Area Telescope

In eight years of operation, the Fermi Large Area Telescope (LAT) has detected a large sample of cosmic-ray protons. The LAT's wide field of view and full-sky coverage make it an excellent instrument for studying anisotropy in the arrival directions of protons at all angular scales. These capabilities enable the LAT to make a full-sky 2D measurement of cosmic-ray proton anisotropy complementary to many recent TeV measurements, which are only sensitive to the right ascension component of the anisotropy. Any detected anisotropy probes the structure of the local interstellar magnetic field or could indicate the presence of a nearby source. We present the first results from the Fermi-LAT Collaboration on the full-sky angular power spectrum of protons from approximately 100 GeV - 10 TeV.

astro-ph.HE↗

arXiv2017

A search for neutrinos from fast radio bursts with IceCube

We present a search for neutrinos in coincidence in time and direction with four fast radio bursts (FRBs) detected by the Parkes and Green Bank radio telescopes during the first year of operation of the complete IceCube Neutrino Observatory (May 2011 through May 2012). The neutrino sample consists of 138,322 muon neutrino candidate events, which are dominated by atmospheric neutrinos and muons but also contain an astrophysical neutrino component. Considering only neutrinos detected on the same day as each FRB, zero IceCube events were found to be compatible with the FRB directions within the estimated 99\% error radius of the neutrino directions. Based on the non-detection, we present the first upper limits on the neutrino fluence from fast radio bursts.

astro-ph.HE↗

arXiv2017

The particle detector in your pocket: The Distributed Electronic Cosmic-ray Observatory

The total area of silicon in cell phone camera sensors worldwide surpasses that in any experiment to date. Based on semiconductor technology similar to that found in modern astronomical telescopes and particle detectors, these sensors can detect ionizing radiation in addition to photons. The Distributed Electronic Cosmic-ray Observatory (DECO) uses the global network of active cell phones in order to detect cosmic rays and other energetic particles such as those produced by radioactive decays. DECO consists of an Android application, database, and public data browser available to citizen scientists around the world (https://wipac.wisc.edu/deco). Candidate cosmic-ray events have been detected on all seven continents and can be categorized by the morphology of their corresponding images. We present the DECO project, a novel particle detector with wide applications in public outreach and education.

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arXiv2017

Evidence against star-forming galaxies as the dominant source of IceCube neutrinos

The cumulative emission resulting from hadronic cosmic-ray interactions in star-forming galaxies (SFGs) has been proposed as the dominant contribution to the astrophysical neutrino flux at TeV to PeV energies reported by IceCube. The same particle interactions also inevitably create $γ$-ray emission that could be detectable as a component of the extragalactic $γ$-ray background (EGB), which is now measured with the Fermi-LAT in the energy range from 0.1 to 820 GeV. New studies of the blazar flux distribution at $γ$-ray energies above 50 GeV place an upper bound on the residual non-blazar component of the EGB. We show that these results are in strong tension with models that consider SFGs as the dominant source of the diffuse neutrino backgrounds. A characteristic spectral index for parent cosmic rays in starburst galaxies of $Γ_{\rm SB} \simeq 2.3$ for $dN/dE \propto E^{-Γ_{\rm SB}}$ is consistent with the observed scaling relation between $γ$-ray and IR luminosity for SFGs, the bounds from the non-blazar EGB, and the observed $γ$-ray spectra of individual starbursts, but underpredicts the IceCube data by approximately an order of magnitude.

astro-ph.HE↗

arXiv2016

Estimating the GeV Emission of Millisecond Pulsars in Dwarf Spheroidal Galaxies

We estimate the conventional astrophysical emission from dwarf spheroidal satellite galaxies (dSphs) of the Milky Way, focusing on millisecond pulsars (MSPs), and evaluate the potential for confusion with dark matter (DM) annihilation signatures at GeV energies. In low-density stellar environments, such as dSphs, the abundance of MSPs is expected to be proportional to stellar mass. Accordingly, we construct the $γ$-ray luminosity function of MSPs in the Milky Way disk, where $>90$ individual MSPs have been detected with the $\textit{Fermi}$ Large Area Telescope (LAT), and scale this luminosity function to the stellar masses of 30 dSphs to estimate the cumulative emission from their MSP populations. We predict that MSPs within the highest stellar mass dSphs, Fornax and Sculptor, produce a $γ$-ray flux $>500$~MeV of $\sim10^{-11}$~ph~cm$^{-2}$~s$^{-1}$, which is a factor $\sim10$ below the current LAT sensitivity at high Galactic latitudes. The MSP emission in ultra-faint dSphs, including targets with the largest J-factors, is typically several orders of magnitude lower, suggesting that these targets will remain clean targets for indirect DM searches in the foreseeable future. For a DM particle of mass 25~GeV annihilating to $b$ quarks at the thermal relic cross section (consistent with DM interpretations of the Galactic Center excess), we find that the expected $γ$-ray emission due to DM exceeds that of MSPs in all of the target dSphs. Using the same Milky Way MSP population model, we also estimate the Galactic foreground MSP coincidence probability along the same sightlines to the dSphs.

astro-ph.HE↗

arXiv2015

Detecting particles with cell phones: the Distributed Electronic Cosmic-ray Observatory

In 2014 the number of active cell phones worldwide for the first time surpassed the number of humans. Cell phone camera quality and onboard processing power (both CPU and GPU) continue to improve rapidly. In addition to their primary purpose of detecting photons, camera image sensors on cell phones and other ubiquitous devices such as tablets, laptops and digital cameras can detect ionizing radiation produced by cosmic rays and radioactive decays. While cosmic rays have long been understood and characterized as a nuisance in astronomical cameras, they can also be identified as a signal in idle camera image sensors. We present the Distributed Electronic Cosmic-ray Observatory (DECO), a platform for outreach and education as well as for citizen science. Consisting of an app and associated database and web site, DECO harnesses the power of distributed camera image sensors for cosmic-ray detection.

astro-ph.IM↗

arXiv2015

Prospects for Measuring the Positron Excess with the Cherenkov Telescope Array

The excess of positrons in cosmic rays above $\sim$10 GeV has been a puzzle since it was discovered. Possible interpretations of the excess have been suggested, including acceleration in a local supernova remnant or annihilation of dark matter particles. To discriminate between these scenarios, the positron fraction must be measured at higher energies. One technique to perform this measurement is using the Earth-Moon spectrometer: observing the deflection of positron and electron moon shadows by the Earth's magnetic field. The measurement has been attempted by previous imaging atmospheric Cherenkov telescopes without success. The Cherenkov Telescope Array (CTA) will have unprecedented sensitivity and background rejection that could make this measurement successful for the first time. In addition, the possibility of using silicon photomultipliers in some of the CTA telescopes could greatly increase the feasibility of making observations near the moon. Estimates of the capabilities of CTA to measure the positron fraction using simulated observations of the moon shadow will be presented.

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arXiv2011

Acoustic detection of astrophysical neutrinos in South Pole ice

When high-energy particles interact in dense media to produce a particle shower, most of the shower energy is deposited in the medium as heat. This causes the medium to expand locally and emit a shock wave with a medium-dependent peak frequency on the order of 10 kHz. In South Pole ice in particular, the elastic properties of the medium have been theorized to provide good coupling of particle energy to acoustic energy. The acoustic attenuation length has been theorized to be several km, which could enable a sparsely instrumented large-volume detector to search for rare signals from high-energy astrophysical neutrinos. We simulated a hybrid optical/radio/acoustic extension to the IceCube array, specifically intended to detect cosmogenic (GZK) neutrinos with multiple methods simultaneously in order to achieve high confidence in a discovered signal and to measure angular, temporal, and spectral distributions of GZK neutrinos. This work motivated the design, deployment, and operation of the South Pole Acoustic Test Setup (SPATS). The main purpose of SPATS is to measure the acoustic attenuation length, sound speed profile, noise floor, and transient noise sources \emph{in situ} at the South Pole. We describe the design, performance, and results from SPATS. We measured the sound speed in the fully dense ice between 200 m and 500 m depth to be 3878 $\pm$ 12 m/s for pressure waves and 1975.8 $\pm$ 8.0 m/s for shear waves. We measured the acoustic amplitude attenuation length to be 316 $\pm$ 105 m. We measured the background noise floor to be Gaussian and very stable on all time scales from one second to two years. Finally, we have detected an interesting set of well-reconstructed transient events in over one year of high quality transient data acquisition. We conclude with a discussion of what is next for SPATS and of the prospects for acoustic neutrino detection in ice.

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