SearcharxivSearch

arXiv subjects

Albrecht Karle

Publications and source records attributed to Albrecht Karle.

At least 19 recordsLinked to original sources

Measuring the Astrophysical Galactic Plane Neutrino Flux and Searching for Galactic PeVatrons using the IceCube Multi-Flavor Astrophysical Neutrino Sample

The IceCube Neutrino Observatory has provided new insights into the high-energy universe, in particular, unveiling neutrinos from the galactic plane. However, galactic neutrino sources are still unresolved. The recent detection of multi-PeV photons by LHAASO from the Cygnus region highlights its potential as a galactic neutrino source. Additionally, LHAASO, HAWC, and HESS have reported over forty galactic gamma-ray sources with energies above 100 TeV. Detecting neutrinos correlated with high-energy gamma-ray sources would provide compelling evidence of cosmic-ray acceleration in these galactic sources. In this work, we compile a 12.3-year, full-sky, all-flavor dataset, the IceCube Multi-Flavor Astrophysics Neutrino sample (ICEMAN). ICEMAN is the combination of three largely independent neutrino samples of different event morphologies and builds upon the previous work of the DNN-based cascade sample, Enhanced Starting Track Event Selection, and the Northern Track sample. Recent improvements in ice modeling and detector calibration are also incorporated into the cascade reconstruction. In addition to revisiting the galactic plane, we adopt two different analysis methods to search for galactic PeVatrons. First, we use a template-based approach to probe the Cygnus Cocoon region. Second, we use a point source hypothesis to find correlations between IceCube neutrinos and gamma-ray sources detected at energies greater than 100 TeV.

astro-ph.HE

Enhancing searches for astrophysical neutrino sources in IceCube with machine learning and improved spatial modeling

Searches for astrophysical neutrino sources in IceCube rely on an unbinned likelihood that consists of an energy and spatial component. Accurate modeling of the detector, ice, and spatial distributions leads to improved directional and energy reconstructions, resulting in increased sensitivity. In this work, we utilize our best knowledge of the detector ice properties and detector calibrations to reconstruct in-ice particle showers. The spatial component of the likelihood is parameterized either by a 2D Gaussian or a von Mises Fisher (vMF) distribution at small and large angular uncertainties, respectively. Here, we use a gradient-boosted decision tree with a vMF spatial likelihood loss function, reparameterized through two coordinate transformations, to predict per-event point spread functions (PSF). Additionally, we discuss the search for PeV cosmic ray sources using the IceCube Multi-Flavor Astrophysical Neutrino (ICEMAN) sample. Our search contains both an analysis of individual neutrino sources coincident with greater than 100 TeV gamma-ray sources and also a stacking analysis. We outline the prospects for extended neutrino emission originating from the Cygnus Cocoon region.

astro-ph.HE

Analysis of the Diffuse Astrophysical Flux from the Galactic Plane with 12.1 Years of IceCube Starting Tracks, Throughgoing Tracks and Cascades

The IceCube Neutrino Observatory has measured an isotropic astrophysical neutrino flux through various detection channels for over 12 years. IceCube has also detected neutrino emission from the Galactic plane at the 4.5$\sigma$ significance level compared to a background-only hypothesis, testing three models of Galactic diffuse emission: Fermi-LAT $\pi^0$, KRA$_{\gamma}^{5}$, KRA$_{\gamma}^{50}$. We present an analysis combining 3 detection channels: throughgoing tracks, starting tracks and cascades. The throughgoing track sample is restricted to the northern sky to reduce atmospheric backgrounds, while the starting track and cascade samples reduce the atmospheric neutrino backgrounds in the southern sky by vetoing accompanying muons. We will use this combination of event samples from 12.1 years of data to measure the Galactic neutrino spectrum in the TeV to PeV energy range and independently for multiple galactic regions in a model independent procedure. We will simultaneously measure the isotropic cosmic neutrino flux.

astro-ph.HE

Measurement of the Three-Flavor Composition of Astrophysical Neutrinos with Contained IceCube Events

The IceCube Neutrino Observatory at the South Pole detects neutrinos from the entire sky, both of astrophysical and atmospheric origin, via the Cherenkov light emitted when these neutrinos interact in the ice, giving rise to rapidly moving charged particles. Neutrino events with vertices contained within the detector volume are useful for studying the neutrino flavor ratio, as they allow for a better reconstruction of the event morphology. The Medium Energy Starting Events (MESE) data sample is a selection of such events with energies of at least 1 TeV. This sample includes electron-, muon-, and tau-neutrino events, processed consistently. We use it to constrain the flavor ratio of astrophysical neutrinos at Earth, which in turn informs us of the flavor composition at the source itself. In this talk, we will present the results of this study, based on 11.4 years of IceCube data.

astro-ph.HE

Measurement of the Diffuse Astrophysical Neutrino Spectrum above a TeV with All Flavor Starting Events in IceCube

The IceCube Neutrino Observatory utilizes the Cherenkov radiation emitted by charged secondary particles produced in interactions of neutrinos with ice nucleons to detect neutrino events. "Starting events", where this interaction vertex is contained inside the detector volume, can be used to distinguish neutrinos from the dominant background of atmospheric through-going muons. We present the Medium Energy Starting Events (MESE) selection, which employs a series of vetoes to obtain a neutrino-pure sample to measure the flux of diffuse extragalactic neutrinos from 1 TeV to 10 PeV from the entire sky. In this talk we will present a measurement of the spectrum of the diffuse flux of neutrinos, which demonstrates strong evidence for structure in the spectrum beyond a single power law, with a significance of $4.2\,\sigma$.

astro-ph.HE

Lake- and Surface-Based Detectors for Forward Neutrino Physics

We propose two medium-baseline, kiloton-scale neutrino experiments to study neutrinos from LHC proton-proton collisions: SINE, a surface-based scintillator panel detector observing muon neutrinos from the CMS interaction point, and UNDINE, a water Cherenkov detector submerged in lake Geneva observing all-flavor neutrinos from LHCb. Using a Monte Carlo simulation, we estimate millions of neutrino interactions during the high-luminosity LHC era. We show that these datasets can constrain neutrino cross sections, charm production in $pp$ collisions, and strangeness enhancement as a solution to the cosmic-ray muon puzzle. SINE and UNDINE thus offer a cost-effective medium-baseline complement to the proposed short-baseline forward physics facility.

hep-ex

Scalable DAQ system operating the CHIPS-5 neutrino detector

The CHIPS R&D project focuses on development of low-cost water Cherenkov neutrino detectors through novel design strategies and resourceful engineering. This work presents an end-to-end DAQ solution intended for a recent 5 kt CHIPS prototype, which is largely based on affordable mass-produced components. Much like the detector itself, the presented instrumentation is composed of modular arrays that can be scaled up and easily serviced. A single such array can carry up to 30 photomultiplier tubes (PMTs) accompanied by electronics that generate high voltage in-situ and deliver time resolution of up to 0.69 ns. In addition, the technology is compatible with the White Rabbit timing system, which can synchronize its elements to within 100 ps. While deployment issues did not permit the presented DAQ system to operate beyond initial evaluation, the presented hardware and software successfully passed numerous commissioning tests that demonstrated their viability for use in a large-scale neutrino detector, instrumented with thousands of PMTs.

physics.ins-det

Report of the Instrumentation Frontier Working Group for Snowmass 2021

Detector instrumentation is at the heart of scientific discoveries. Cutting edge technologies enable US particle physics to play a leading role worldwide. This report summarizes the current status of instrumentation for High Energy Physics (HEP), the challenges and needs of future experiments and indicates high priority research areas. The Snowmass Instrumentation Frontier studies detector technologies and Research and Development (R&D) needed for future experiments in collider physics, neutrino physics, rare and precision physics and at the cosmic frontier. It is divided into more or less diagonal areas with some overlap among a few of them. We lay out five high-level key messages that are geared towards ensuring the health and competitiveness of the US detector instrumentation community, and thus the entire particle physics landscape.

hep-ex

Concept Study of a Radio Array Embedded in a Deep Gen2-like Optical Array

The IceCube Neutrino Observatory has discovered a diffuse astrophysical flux up to 10 PeV and is now planning a large extension with IceCube-Gen2, including an optical array and a large radio array at shallow depth [1]. Neutrino searches for energies >100 PeV are best done with such shallow radio detectors like the Askaryan Radio Array (ARA) or similar (buried as deep as 200 meters below the surface) as they are cheaper to deploy. This poster explores the potential of opportunistically burying radio antennas within the planned IceCube-Gen2 detector volume (between 1350 meters and 2600 meters below the surface). A hybrid detection of events in optical and radio could substantially improve the uncertainty of neutrino cascade direction as radio signals do not scatter in ice. We show the first results of simulating neutrinos from an astrophysical and a cosmogenic flux interacting with 9760 ARA-style vertically polarized radio antennas distributed evenly across 122 strings.

astro-ph.HE

A Method for an Untriggered, Time-Dependent, Source-Stacking Search for Neutrino Flares

Recent results from IceCube regarding TXS 0506+056 suggest that it may be useful to test the hypothesis of multiple neutrino flares, where each flare is not necessarily accompanied by a corresponding gamma-ray flare. An untriggered, time-dependent, source-stacking search would be optimal for testing this hypothesis, however such an analysis has yet to be applied to the full duration of IceCube data. Here, we discuss one possible way of constructing such an analysis, with a global test statistic obtained by summing the individual test statistics associated with each signal-like flare in the sample. This has the additional advantage of assessing the time structure of each source when running the analysis over a source catalog. We show that, for a signal consisting of many small flares, this style of analysis represents a significant increase in discovery potential over both the existing single-flare fit and the time-integrated stacking methods. Potential source catalogs are examined in combination with this method, including the possibility of a "self-triggered" catalog consisting of the locations of the highest energy northern sky events in the IceCube sample.

astro-ph.HE

Astrophysics Uniquely Enabled by Observations of High-Energy Cosmic Neutrinos

High-energy cosmic neutrinos carry unique information about the most energetic non-thermal sources in the Universe. This white paper describes the outstanding astrophysics questions that neutrino astronomy can address in the coming decade. A companion white paper discusses how the observation of cosmic neutrinos can address open questions in fundamental physics. Detailed measurements of the diffuse neutrino flux, measurements of neutrinos from point sources, and multi-messenger observations with neutrinos will enable the discovery and characterization of the most energetic sources in the Universe.

astro-ph.HE

Fundamental Physics with High-Energy Cosmic Neutrinos

High-energy cosmic neutrinos can reveal new fundamental particles and interactions, probing energy and distance scales far exceeding those accessible in the laboratory. This white paper describes the outstanding particle physics questions that high-energy cosmic neutrinos can address in the coming decade. A companion white paper discusses how the observation of cosmic neutrinos can address open questions in astrophysics. Tests of fundamental physics using high-energy cosmic neutrinos will be enabled by detailed measurements of their energy spectrum, arrival directions, flavor composition, and timing.

astro-ph.HE

A generalized self-veto probability for atmospheric neutrinos

Neutrino telescopes such as IceCube search for an excess of high energy neutrinos above the steeply falling atmospheric background as one approach to finding extraterrestrial neutrinos. For samples of events selected to start in the detector, the atmospheric background can be reduced to the extent that a neutrino interaction inside the fiducial volume is accompanied by a detectable muon from the same cosmic-ray cascade in which the neutrino was produced. Here we provide an approximate calculation of the veto probability as a function of neutrino energy and zenith angle.

astro-ph.HE

Neutrino Astronomy - A Review of Future Experiments

Current generation neutrino telescopes cover an energy range from about 10 GeV to beyond $10^9$ GeV. IceCube sets the scale for future experiments to make improvements. Strategies for future upgrades will be discussed in three energy ranges. At the low-energy end, an infill detector to IceCube's DeepCore would add sensitivity in the energy range from a few to a few tens of GeV with the primary goal of measuring the neutrino mass hierarchy. In the central energy range of classical optical neutrino telescopes, next generation detectors are being pursued in the Mediterranean and at Lake Baikal. The KM3NeT detector in its full scale would establish a substantial increase in sensitivity over IceCube. At the highest energies, radio detectors in ice are among the most promising and pursued technologies to increase exposure at $10^9$ GeV by more than an order of magnitude compared to IceCube.

astro-ph.IM

Study of electromagnetic backgrounds in the 25-300 MHz frequency band at the South Pole

Extensive air showers are detectable by radio signals with a radio surface detector. A promising theory of the dominant emission process is the coherent synchrotron radiation emitted by e+ e- shower particles in the Earth's magnetic field (geosynchrotron effect). A radio air shower detector can extend IceTop, the air shower detector on top of IceCube. This could increase the sensitivity of IceTop to higher shower energies and for inclined showers significantly. Muons from air showers are a major part of the background of the neutrino telescope IceCube. Thus a surface radio air shower detector could act as a veto detector for this muonic background. Initial radio background measurements with a single antenna in 2007 revealed a continuous electromagnetic background promising a low energy threshold of radio air shower detection. However, short pulsed radio interferences can mimic real signals and have to be identified in the frequency range of interest. These properties of the electromagnetic background was being measured at the South Pole during the Antarctic winter 2009 with two different types of surface antennas. In total four antennas are placed at distances ranging up to 400m from each other. In 2010 a small eight channel surface detector will test an amplitude threshold self trigger strategy with large dipole antennas on the South Pole snow ground. The installation will be described.

astro-ph.IM

Time-Dependent Point Source Search Methods in High Energy Neutrino Astronomy

We present maximum-likelihood search methods for time-dependent fluxes from point sources, such as flares or periodic emissions. We describe a method for the case when the time dependence of the flux can be assumed a priori from other observations, and we additionally describe a method to search for bursts with an unknown time dependence. In the context of high energy neutrino astronomy, we simulate one year of data from a cubic-kilometer scale neutrino detector and characterize these methods and equivalent binned methods with respect to the duration of neutrino emission. Compared to standard time-integrated searches, we find that up to an order of magnitude fewer events are needed to discover bursts with short durations, even when the burst time and duration are not known a priori.

astro-ph.IM

IceCube: Construction Status and First Results

IceCube is a 1 km3 neutrino telescope currently under construction at the South Pole. The detector will consist of 4800 optical sensors deployed at depths between 1450 m and 2450 m in clear Antarctic ice evenly distributed over 80 strings. An air shower array covering a surface area of 1 km^2 above the in-ice detector will measure cosmic ray air showers in the energy range from 300 TeV to above 1 EeV. The detector is designed to detect neutrinos of all flavors. With 40 strings currently in operation, construction is 50% complete. Based on data taken to date, the observatory meets its design goals and currently exceeds the sensitivity of AMANDA and previous neutrino telescopes. The construction outlook and possible future extensions are also discussed.

astro-ph

Methods for point source analysis in high energy neutrino telescopes

Neutrino telescopes are moving steadily toward the goal of detecting astrophysical neutrinos from the most powerful galactic and extragalactic sources. Here we describe analysis methods to search for high energy point-like neutrino sources using detectors deep in the ice or sea. We simulate an ideal cubic kilometer detector based on real world performance of existing detectors such as AMANDA, IceCube, and ANTARES. An unbinned likelihood ratio method is applied, making use of the point spread function and energy distribution of simulated neutrino signal events to separate them from the background of atmospheric neutrinos produced by cosmic ray showers. The unbinned point source analyses are shown to perform better than binned searches and, depending on the source spectral index, the use of energy information is shown to improve discovery potential by almost a factor of two.

astro-ph