190 research outputs found
К вопросу о кипении жидкости с подводом тепла через стенку
The application of digital holographic microscopy offers quantitative phase contrast imaging of reflective and (partially) transparent samples. Low coherent light sources enable an increased resolution in phase shifting digital holography by the reduction of stray light and multiple reflections in the experimental interferometer setup. Therefore light emitting diodes (LED) are utilized. Here, the effects on the reconstruction quality by considering the whole spectrum of the light source are investigated. Furthermore, the propagation of the complex wave fronts, which are determined by digital holography, and used for re- and multifocusing, is modified to light sources with a spectral width wider than that of typical laser light sources. Therefore, the propagation algorithm using the convolution method as a solution of the Fresnel-Kirchhoff diffraction integral according to the first Rayleigh-Sommerfeld approximation is extended by an additional integral to take into account the spectral width of low coherent light sources. Numerically, in the new approach the supplementary integral is realized by a discrete sum considering a finite set of wavelengths. Specifically, the results of the modified algorithm are compared with common algorithms with respect to resolution and image sharpness
Measurement of atmospheric neutrino mixing with improved IceCube DeepCore calibration and data processing
We describe a new data sample of IceCube DeepCore and report on the latest measurement of atmospheric neutrino oscillations obtained with data recorded between 2011–2019. The sample includes significant improvements in data calibration, detector simulation, and data processing, and the analysis benefits from a sophisticated treatment of systematic uncertainties, with significantly greater level of detail since our last study. By measuring the relative fluxes of neutrino flavors as a function of their reconstructed energies and arrival directions we constrain the atmospheric neutrino mixing parameters to be sin2θ23=0.51±0.05 and Δm232=2.41±0.07×10−3 eV2, assuming a normal mass ordering. The errors include both statistical and systematic uncertainties. The resulting 40% reduction in the error of both parameters with respect to our previous result makes this the most precise measurement of oscillation parameters using atmospheric neutrinos. Our results are also compatible and complementary to those obtained using neutrino beams from accelerators, which are obtained at lower neutrino energies and are subject to different sources of uncertainties
A muon-track reconstruction exploiting stochastic losses for large-scale Cherenkov detectors
IceCube is a cubic-kilometer Cherenkov telescope operating at the South Pole.
The main goal of IceCube is the detection of astrophysical neutrinos and the
identification of their sources. High-energy muon neutrinos are observed via
the secondary muons produced in charge current interactions with nuclei in the
ice. Currently, the best performing muon track directional reconstruction is
based on a maximum likelihood method using the arrival time distribution of
Cherenkov photons registered by the experiment's photomultipliers. A known
systematic shortcoming of the prevailing method is to assume a continuous
energy loss along the muon track. However at energies TeV the light yield
from muons is dominated by stochastic showers. This paper discusses a
generalized ansatz where the expected arrival time distribution is parametrized
by a stochastic muon energy loss pattern. This more realistic parametrization
of the loss profile leads to an improvement of the muon angular resolution of
up to for through-going tracks and up to a factor 2 for starting tracks
over existing algorithms. Additionally, the procedure to estimate the
directional reconstruction uncertainty has been improved to be more robust
against numerical errors
Measurement of Atmospheric Neutrino Mixing with Improved IceCube DeepCore Calibration and Data Processing
We describe a new data sample of IceCube DeepCore and report on the latest
measurement of atmospheric neutrino oscillations obtained with data recorded
between 2011-2019. The sample includes significant improvements in data
calibration, detector simulation, and data processing, and the analysis
benefits from a detailed treatment of systematic uncertainties, with
significantly higher level of detail since our last study. By measuring the
relative fluxes of neutrino flavors as a function of their reconstructed
energies and arrival directions we constrain the atmospheric neutrino mixing
parameters to be and , assuming a normal mass ordering. The
resulting 40\% reduction in the error of both parameters with respect to our
previous result makes this the most precise measurement of oscillation
parameters using atmospheric neutrinos. Our results are also compatible and
complementary to those obtained using neutrino beams from accelerators, which
are obtained at lower neutrino energies and are subject to different sources of
uncertainties
Limits on Neutrino Emission from GRB 221009A from MeV to PeV using the IceCube Neutrino Observatory
Gamma-ray bursts (GRBs) have long been considered a possible source of
high-energy neutrinos. While no correlations have yet been detected between
high-energy neutrinos and GRBs, the recent observation of GRB 221009A - the
brightest GRB observed by Fermi-GBM to date and the first one to be observed
above an energy of 10 TeV - provides a unique opportunity to test for hadronic
emission. In this paper, we leverage the wide energy range of the IceCube
Neutrino Observatory to search for neutrinos from GRB 221009A. We find no
significant deviation from background expectation across event samples ranging
from MeV to PeV energies, placing stringent upper limits on the neutrino
emission from this source.Comment: Version in ApJ Letters Focus on the Ultra-luminous Gamma-Ray Burst
GRB 221009
Constraining High-energy Neutrino Emission from Supernovae with IceCube
Core-collapse supernovae are a promising potential high-energy neutrino source class. We test for correlation between seven years of IceCube neutrino data and a catalog containing more than 1000 core-collapse supernovae of types IIn and IIP and a sample of stripped-envelope supernovae. We search both for neutrino emission from individual supernovae, and for combined emission from the whole supernova sample through a stacking analysis. No significant spatial or temporal correlation of neutrinos with the cataloged supernovae was found. The overall deviation of all tested scenarios from the background expectation yields a p-value of 93% which is fully compatible with background. The derived upper limits on the total energy emitted in neutrinos are 1.7×10 erg for stripped-envelope supernovae, 2.8×10 erg for type IIP, and 1.3×10 erg for type IIn SNe, the latter disfavouring models with optimistic assumptions for neutrino production in interacting supernovae. We conclude that strippe-envelope supernovae and supernovae of type IIn do not contribute more than 14.6% and 33.9% respectively to the diffuse neutrino flux in the energy range of about 10−10 GeV, assuming that the neutrino energy spectrum follows a power-law with an index of −2.5. Under the same assumption, we can only constrain the contribution of type IIP SNe to no more than 59.9%. Thus core-collapse supernovae of types IIn and stripped-envelope supernovae can both be ruled out as the dominant source of the diffuse neutrino flux under the given assumptions
A Search for Coincident Neutrino Emission from Fast Radio Bursts with Seven Years of IceCube Cascade Events
This paper presents the results of a search for neutrinos that are spatially
and temporally coincident with 22 unique, non-repeating Fast Radio Bursts
(FRBs) and one repeating FRB (FRB121102). FRBs are a rapidly growing class of
Galactic and extragalactic astrophysical objects that are considered a
potential source of high-energy neutrinos. The IceCube Neutrino Observatory's
previous FRB analyses have solely used track events. This search utilizes seven
years of IceCube's cascade events which are statistically independent of the
track events. This event selection allows probing of a longer range of extended
timescales due to the low background rate. No statistically significant
clustering of neutrinos was observed. Upper limits are set on the
time-integrated neutrino flux emitted by FRBs for a range of extended
time-windows
Testing Hadronic Interaction Models with Cosmic Ray Measurements at the IceCube Neutrino Observatory
The IceCube Neutrino Observatory provides the opportunity to perform unique measurements of cosmic-ray air showers with its combination of a surface array and a deep detector. Electromagnetic particles and low-energy muons (∼GeV) are detected by IceTop, while a bundle of high-energy muons (>~400 GeV) can be measured in coincidence in IceCube. Predictions of air-shower observables based on simulations show a strong dependence on the choice of the high-energy hadronic interaction model. By reconstructing different composition-dependent observables, one can provide strong tests of hadronic interaction models, as these measurements should be consistent with one another. In this work, we present an analysis of air-shower data between 2.5 and 80 PeV, comparing the composition interpretation of measurements of the surface muon density, the slope of the IceTop lateral distribution function, and the energy loss of the muon bundle, using the models Sibyll 2.1, QGSJet-II.04 and EPOS-LHC. We observe inconsistencies in all models under consideration, suggesting they do not give an adequate description of experimental data. The results furthermore imply a significant uncertainty in the determination of the cosmic-ray mass composition through indirect measurements
Search for Extended Sources of Neutrino Emission in the Galactic Plane with IceCube
The Galactic plane, harboring a diffuse neutrino flux, is a particularly
interesting target to study potential cosmic-ray acceleration sites. Recent
gamma-ray observations by HAWC and LHAASO have presented evidence for multiple
Galactic sources that exhibit a spatially extended morphology and have energy
spectra continuing beyond 100 TeV. A fraction of such emission could be
produced by interactions of accelerated hadronic cosmic rays, resulting in an
excess of high-energy neutrinos clustered near these regions. Using 10 years of
IceCube data comprising track-like events that originate from charged-current
muon neutrino interactions, we perform a dedicated search for extended neutrino
sources in the Galaxy. We find no evidence for time-integrated neutrino
emission from the potential extended sources studied in the Galactic plane. The
most significant location, at 2.6 post-trials, is a 1.7 sized
region coincident with the unidentified TeV gamma-ray source 3HWC J1951+266. We
provide strong constraints on hadronic emission from several regions in the
Galaxy.Comment: 13 pages, 4 figures, 5 tables including an appendix. Accepted for
publication in Astrophysical Journa
Constraining High-energy Neutrino Emission from Supernovae with IceCube
Core-collapse supernovae are a promising potential high-energy neutrino source class. We test for correlation between seven years of IceCube neutrino data and a catalog containing more than 1000 core-collapse supernovae of types IIn and IIP and a sample of stripped-envelope supernovae. We search both for neutrino emission from individual supernovae as well as for combined emission from the whole supernova sample, through a stacking analysis. No significant spatial or temporal correlation of neutrinos with the cataloged supernovae was found. All scenarios were tested against the background expectation and together yield an overall p-value of 93%; therefore, they show consistency with the background only. The derived upper limits on the total energy emitted in neutrinos are 1.7 × 10 erg for stripped-envelope supernovae, 2.8 × 10 erg for type IIP, and 1.3 × 10 erg for type IIn SNe, the latter disfavoring models with optimistic assumptions for neutrino production in interacting supernovae. We conclude that stripped-envelope supernovae and supernovae of type IIn do not contribute more than 14.6% and 33.9%, respectively, to the diffuse neutrino flux in the energy range of about [ 10–10] GeV, assuming that the neutrino energy spectrum follows a power-law with an index of −2.5. Under the same assumption, we can only constrain the contribution of type IIP SNe to no more than 59.9%. Thus, core-collapse supernovae of types IIn and stripped-envelope supernovae can both be ruled out as the dominant source of the diffuse neutrino flux under the given assumptions
- …