arXiv subjects

E. Eckerová

Publications and source records attributed to E. Eckerová.

At least 37 records · Page 2Linked to original sources

arXiv2024

Measurement of neutrino oscillation parameters with the first six detection units of KM3NeT/ORCA

KM3NeT/ORCA is a water Cherenkov neutrino detector under construction and anchored at the bottom of the Mediterranean Sea. The detector is designed to study oscillations of atmospheric neutrinos and determine the neutrino mass ordering. This paper focuses on an initial configuration of ORCA, referred to as ORCA6, which comprises six out of the foreseen 115 detection units of photo-sensors. A high-purity neutrino sample was extracted, corresponding to an exposure of 433 kton-years. The sample of 5828 neutrino candidates is analysed following a binned log-likelihood method in the reconstructed energy and cosine of the zenith angle. The atmospheric oscillation parameters are measured to be $\sin^2θ_{23}= 0.51^{+0.04}_{-0.05}$, and $ Δm^2_{31} = 2.18^{+0.25}_{-0.35}\times 10^{-3}~\mathrm{eV^2} \cup \{-2.25,-1.76\}\times 10^{-3}~\mathrm{eV^2}$ at 68\% CL. The inverted neutrino mass ordering hypothesis is disfavoured with a p-value of 0.25.

hep-ex↗

arXiv2024

Searches for neutrino counterparts of gravitational waves from the LIGO/Virgo third observing run with KM3NeT

The KM3NeT neutrino telescope is currently being deployed at two different sites in the Mediterranean Sea. First searches for astrophysical neutrinos have been performed using data taken with the partial detector configuration already in operation. The paper presents the results of two independent searches for neutrinos from compact binary mergers detected during the third observing run of the LIGO and Virgo gravitational wave interferometers. The first search looks for a global increase in the detector counting rates that could be associated with inverse beta decay events generated by MeV-scale electron anti-neutrinos. The second one focuses on upgoing track-like events mainly induced by muon (anti-)neutrinos in the GeV--TeV energy range. Both searches yield no significant excess for the sources in the gravitational wave catalogs. For each source, upper limits on the neutrino flux and on the total energy emitted in neutrinos in the respective energy ranges have been set. Stacking analyses of binary black hole mergers and neutron star-black hole mergers have also been performed to constrain the characteristic neutrino emission from these categories.

astro-ph.HE↗

arXiv2024

Search for Neutrino Emission from GRB 221009A using the KM3NeT ARCA and ORCA detectors

Gamma-ray bursts are promising candidate sources of high-energy astrophysical neutrinos. The recent GRB 221009A event, identified as the brightest gamma-ray burst ever detected, provides a unique opportunity to investigate hadronic emissions involving neutrinos. The KM3NeT undersea neutrino detectors participated in the worldwide follow-up effort triggered by the event, searching for neutrino events. In this letter, we summarize subsequent searches, in a wide energy range from MeV up to a few PeVs. No neutrino events are found in any of the searches performed. Upper limits on the neutrino emission associated with GRB 221009A are computed.

astro-ph.HE↗

arXiv2024

Prospects for combined analyses of hadronic emission from $γ$-ray sources in the Milky Way with CTA and KM3NeT

The Cherenkov Telescope Array and the KM3NeT neutrino telescopes are major upcoming facilities in the fields of $γ$-ray and neutrino astronomy, respectively. Possible simultaneous production of $γ$ rays and neutrinos in astrophysical accelerators of cosmic-ray nuclei motivates a combination of their data. We assess the potential of a combined analysis of CTA and KM3NeT data to determine the contribution of hadronic emission processes in known Galactic $γ$-ray emitters, comparing this result to the cases of two separate analyses. In doing so, we demonstrate the capability of Gammapy, an open-source software package for the analysis of $γ$-ray data, to also process data from neutrino telescopes. For a selection of prototypical $γ$-ray sources within our Galaxy, we obtain models for primary proton and electron spectra in the hadronic and leptonic emission scenario, respectively, by fitting published $γ$-ray spectra. Using these models and instrument response functions for both detectors, we employ the Gammapy package to generate pseudo data sets, where we assume 200 hours of CTA observations and 10 years of KM3NeT detector operation. We then apply a three-dimensional binned likelihood analysis to these data sets, separately for each instrument and jointly for both. We find that the largest benefit of the combined analysis lies in the possibility of a consistent modelling of the $γ$-ray and neutrino emission. Assuming a purely leptonic scenario as input, we obtain, for the most favourable source, an average expected 68% credible interval that constrains the contribution of hadronic processes to the observed $γ$-ray emission to below 15%.

astro-ph.HE↗

arXiv2023

Track-Like Event Analysis at the Baikal-GVD Neutrino Telescope

Reconstructed tracks of muons produced in neutrino interactions provide the precise probe for the neutrino direction. Therefore, track-like events are a powerful tool to search for neutrino point sources. Recently, Baikal-GVD has demonstrated the first sample of low-energy neutrino candidate events extracted from the data of the season 2019 in a so-called single-cluster analysis - treating each cluster as an independent detector. In this paper, the extension of the track-like event analysis to a wider data set is discussed and the first high-energy track-like events are demonstrated. The status of multi-cluster track reconstruction and that of the event analysis are also discussed.

astro-ph.IM↗

arXiv2023

Atmospheric muon suppression for Baikal-GVD cascade analysis

Baikal-GVD (Gigaton Volume Detector) is a neutrino telescope installed at a depth of 1366 m in Lake Baikal. The expedition of 2023 brought the number of optical modules in the array up to 3492 (including experimental strings). These optical modules detect the Cherenkov radiation from secondary charged particles coming from the neutrino interactions. Neutrinos produce different kinds of topologically distinct light signatures. Charged current muon neutrino interactions create an elongated track in the water. Charged and neutral current interactions of other neutrino flavors yield hadronic and electromagnetic cascades. The background in the neutrino cascade channel arises mainly due to discrete stochastic energy losses produced along atmospheric muon tracks. In this paper, a developed algorithm for the cascade event selection is presented.

astro-ph.IM↗

arXiv2023

Improving the efficiency of cascade detection by the Baikal-GVD neutrino telescope

The deployment of the Baikal-GVD deep underwater neutrino telescope is in progress now. About 3500 deep underwater photodetectors (optical modules) arranged into 12 clusters are operating in Lake Baikal. For increasing the efficiency of cascade-like neutrino event detection, the telescope deployment scheme was slightly changed. Namely, the inter-cluster distance was reduced for the newly deployed clusters and additional string of optical modules are added between the clusters. The first inter-cluster string was installed in 2022 and two such strings were installed in 2023. This paper presents a Monte Carlo estimate of the impact of these configuration changes on the cascade detection efficiency as well as technical implementation and results of in-situ tests of the inter-cluster strings.

astro-ph.IM↗

arXiv2023

Diffuse neutrino flux measurements with the Baikal-GVD neutrino telescope

Baikal-GVD is a next generation, kilometer-scale neutrino telescope currently under construction in Lake Baikal. GVD consists of multi-megaton subarrays (clusters) and is designed for the detection of astrophysical neutrino fluxes at energies from a few TeV up to 100 PeV. The large detector volume and modular design of Baikal-GVD allows for the measurements of the astrophysical diffuse neutrino flux to be performed already at early phases of the array construction. We present here recent results of the measurements on the diffuse cosmic neutrino flux obtained with the Baikal-GVD neutrino telescope using cascade-like events.

astro-ph.HE↗

arXiv2023

Double cascade reconstruction in the Baikal-GVD neutrino telescope

Baikal Gigaton Volume Detector is a cubic kilometer scale neutrino telescope under construction in Lake Baikal. As of July 2023, Baikal-GVD consists of 96 fully deployed strings resulting in 3456 optical modules installed. The observation of neutrinos is based on detection of Cherenkov radiation emitted by the products of neutrino interactions. In this contribution, description of the double cascade reconstruction technique as well as evaluation of precision of this algorithm is given.

astro-ph.IM↗

arXiv2023

Large neutrino telescope Baikal-GVD: recent status

The Baikal-GVD is a deep-underwater neutrino telescope being constructed in Lake Baikal. After the winter 2023 deployment campaign the detector consists of 3456 optical modules installed on 96 vertical strings. The status of the detector and progress in data analysis are discussed in present report. The Baikal-GVD data collected in 2018-2022 indicate the presence of cosmic neutrino flux in high-energy cascade events consistent with observations by the IceCube neutrino telescope. Analysis of track-like events results in identification of first high-energy muon neutrino candidates. These and other results from 2018-2022 data samples are reviewed in this report.

astro-ph.HE↗

arXiv2023

Monitoring of optical properties of deep waters of Lake Baikal in 2021-2022

We present the results of the two-year (2021-2022) monitoring of absorption and scattering lengths of light with wavelength 400-620 nm within the effective volume of the deep underwater neutrino telescope Baikal-GVD, which were measured by a device Baikal-5D No.2. The Baikal-5D No.2. was installed during the 2021 winter expedition at a depth of 1180 m. The absorption and scattering lengths were measured every week in 9 spectral points. The device Baikal-5D No.2 also has the ability to measure detailed scattering and absorption spectra. The data obtained make it possible to estimate the range of changes in the absorption and scattering lengths over a sufficiently long period of time and to investigate the relationship between the processes of changes in absorption and scattering. An analysis was made of changes in absorption and scattering spectra for the period 2021-2022.

hep-ph↗

arXiv2023

Studies of the ambient light of deep Baikal waters with Baikal-GVD

The Baikal-GVD neutrino detector is a deep-underwater neutrino telescope under construction and recently after the winter 2023 deployment it consists of 3456 optical modules attached on 96 vertical strings. This 3-dimensional array of photo-sensors allows to observe ambient light in the vicinity of the Baikal-GVD telescope that is associated mostly with water luminescence. Results on time and space variations of the luminescent activity are reviewed based on data collected in 2018-2022.

hep-ph↗

arXiv2023

Time Calibration of the Baikal-GVD Neutrino Telescope with Atmospheric Muons

We present a new procedure for time calibration of the Baikal-GVD neutrino telescope. The track reconstruction quality depends on accurate measurements of arrival times of Cherenkov photons. Therefore, it is crucial to achieve a high precision in time calibration. For that purpose, in addition to other calibration methods, we employ a new procedure using atmospheric muons reconstructed in a single-cluster mode. The method is based on iterative determination of effective time offsets for each optical module. This paper focuses on the results of the iterative reconstruction procedure with time offsets from the previous iteration and the verification of the method developed. The theoretical muon calibration precision is estimated to be around 1.5-1.6ns.

astro-ph.IM↗

arXiv2023

Search for directional associations between Baikal Gigaton Volume Detector neutrino-induced cascades and high-energy astrophysical sources

Baikal-GVD has recently published its first measurement of the diffuse astrophysical neutrino flux, performed using high-energy cascade-like events. We further explore the Baikal-GVD cascade dataset collected in 2018-2022, with the aim to identify possible associations between the Baikal-GVD neutrinos and known astrophysical sources. We leverage the relatively high angular resolution of the Baikal-GVD neutrino telescope (2-3 deg.), made possible by the use of liquid water as the detection medium, enabling the study of astrophysical point sources even with cascade events. We estimate the telescope's sensitivity in the cascade channel for high-energy astrophysical sources and refine our analysis prescriptions using Monte-Carlo simulations. We primarily focus on cascades with energies exceeding 100 TeV, which we employ to search for correlation with radio-bright blazars. Although the currently limited neutrino sample size provides no statistically significant effects, our analysis suggests a number of possible associations with both extragalactic and Galactic sources. Specifically, we present an analysis of an observed triplet of neutrino candidate events in the Galactic plane, focusing on its potential connection with certain Galactic sources, and discuss the coincidence of cascades with several bright and flaring blazars.

astro-ph.HE↗

arXiv2023

Baikal-GVD Real-Time Data Processing and Follow-Up Analysis of GCN Notices

The Baikal-GVD alert system was launched at the beginning of 2021. There are alerts for muon neutrinos (long upward-going track-like events) and all-flavour neutrinos (high-energy cascades). The system is able to get a preliminary response to external alerts with a temporal delay of about 3-10 minutes. The Baikal-GVD data processing and the results of the follow-up procedure are described. We report on the analysis of the coincidence in time and direction between the Baikal-GVD cascade GVD20211208CA with an estimated energy of 43 TeV and the announced alert IceCube211208A possibly associated with a flaring state of the blazar PKS 0735+178.

astro-ph.HE↗

arXiv2023

Baikal-GVD Astrophysical Neutrino Candidate near the Blazar TXS~0506+056

We report on the observation of a rare neutrino event detected by Baikal-GVD in April 2021. The event GVD210418CA is the highest-energy cascade observed by Baikal-GVD so far from the direction below the horizon. The estimated cascade energy is $224\pm75$~TeV. The evaluated signalness parameter of GVD210418CA is 97.1\% using an assumption of the E$^{-2.46}$ spectrum of astrophysical neutrinos. The arrival direction of GVD210418CA is near the position of the well-known radio blazar TXS~0506+056, with the angular distance being within a 90\% directional uncertainty region of the Baikal-GVD measurement. The event was followed by a radio flare observed by the RATAN-600 radio telescope, further strengthening the case for the neutrino-blazar association.

astro-ph.HE↗

arXiv2022

Increasing the sensitivity of the Baikal-GVD neutrino telescope by using external strings of optical modules

The deployment of the Baikal-GVD deep underwater neutrino telescope is continuing in Lake Baikal. By April 2022, ten clusters of the telescope were put into operation, with 2880 optical modules in total. One of the relevant tasks in this context is to study the possibilities of increasing the efficiency of the detector based on the experience of its operation and the results obtained at other neutrino telescopes in recent years. In this paper, a variant of optimizing the configuration of the telescope is considered, based on the installation of additional strings of optical modules between the clusters (external strings). An experimental version of the external string was installed in Lake Baikal in April 2022. This paper presents a first estimate of the impact of adding external strings on the neutrino detection efficiency, as well as the technical implementation of the detection and data acquisition systems of the external string and first results of its in-situ tests.

hep-ex↗

arXiv2022

Diffuse neutrino flux measurements with the Baikal-GVD neutrino telescope

We report on the first observation of the diffuse cosmic neutrino flux with the Baikal-GVD neutrino telescope. Using cascade-like events collected by Baikal-GVD in 2018--2021, a significant excess of events over the expected atmospheric background is observed. This excess is consistent with the high-energy diffuse cosmic neutrino flux observed by IceCube. The null cosmic flux assumption is rejected with a significance of 3.05$σ$. Assuming a single power law model of the astrophysical neutrino flux with identical contribution from each neutrino flavor, the following best-fit parameter values are found: the spectral index $γ_{astro}$ = $2.58^{+0.27}_{-0.33}$ and the flux normalization $ϕ_{astro}$ = 3.04$^{+1.52}_{-1.21}$ per one flavor at 100 TeV.

astro-ph.HE↗