The next generation of water Cherenkov neutrino telescopes in the Mediterranean Sea are under construction offshore France (KM3NeT/ORCA) and Sicily (KM3NeT/ARCA). The KM3NeT/ORCA detector features an ...energy detection threshold which allows to collect atmospheric neutrinos to study flavour oscillation. This paper reports the KM3NeT/ORCA sensitivity to this phenomenon. The event reconstruction, selection and classification are described. The sensitivity to determine the neutrino mass ordering was evaluated and found to be 4.4
σ
if the true ordering is normal and 2.3
σ
if inverted, after 3 years of data taking. The precision to measure
Δ
m
32
2
and
θ
23
were also estimated and found to be
85
.
10
-
6
eV
2
and
(
-
3.1
+
1.9
)
∘
for normal neutrino mass ordering and,
75
.
10
-
6
eV
2
and
(
-
7.0
+
2.0
)
∘
for inverted ordering. Finally, a unitarity test of the leptonic mixing matrix by measuring the rate of tau neutrinos is described. Three years of data taking were found to be sufficient to exclude
event rate variations larger than 20% at
3
σ
level.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A
bstract
In the era of precision measurements of the neutrino oscillation parameters, upcoming neutrino experiments will also be sensitive to physics beyond the Standard Model. KM3NeT/ORCA is a ...neutrino detector optimised for measuring atmospheric neutrinos from a few GeV to around 100 GeV. In this paper, the sensitivity of the KM3NeT/ORCA detector to neutrino decay has been explored. A three-flavour neutrino oscillation scenario, where the third neutrino mass state
ν
3
decays into an invisible state, e.g. a sterile neutrino, is considered. We find that KM3NeT/ORCA would be sensitive to invisible neutrino decays with 1
/α
3
=
τ
3
/m
3
<
180 ps
/
eV at 90% confidence level, assuming true normal ordering. Finally, the impact of neutrino decay on the precision of KM3NeT/ORCA measurements for
θ
23
,
Δ
m
31
2
and mass ordering have been studied. No significant effect of neutrino decay on the sensitivity to these measurements has been found.
The KM3NeT research infrastructure is under construction in the Mediterranean Sea. It consists of two water Cherenkov neutrino detectors, ARCA and ORCA, aimed at neutrino astrophysics and oscillation ...research, respectively. Instrumenting a large volume of sea water with Formula omitted optical modules comprising a total of Formula omitted photomultiplier tubes, KM3NeT will achieve sensitivity to Formula omitted neutrinos from Galactic and near-Galactic core-collapse supernovae through the observation of coincident hits in photomultipliers above the background. In this paper, the sensitivity of KM3NeT to a supernova explosion is estimated from detailed analyses of background data from the first KM3NeT detection units and simulations of the neutrino signal. The KM3NeT observational horizon (for a Formula omitted discovery) covers essentially the Milky-Way and for the most optimistic model, extends to the Small Magellanic Cloud ( Formula omitted). Detailed studies of the time profile of the neutrino signal allow assessment of the KM3NeT capability to determine the arrival time of the neutrino burst with a few milliseconds precision for sources up to 5-8 kpc away, and detecting the peculiar signature of the standing accretion shock instability if the core-collapse supernova explosion happens closer than 3-5 kpc, depending on the progenitor mass. KM3NeT's capability to measure the neutrino flux spectral parameters is also presented.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The KM3NeT research infrastructure is unconstruction in the Mediterranean Sea. KM3NeT will study atmospheric and astrophysical neutrinos with two multi-purpose neutrino detectors, ARCA and ORCA, ...primarily aimed at GeV–PeV neutrinos. Thanks to the multi-photomultiplier tube design of the digital optical modules, KM3NeT is capable of detecting the neutrino burst from a Galactic or near-Galactic core-collapse supernova. This potential is already exploitable with the first detection units deployed in the sea. This paper describes the real-time implementation of the supernova neutrino search, operating on the two KM3NeT detectors since the first months of 2019. A quasi-online astronomy analysis is introduced to study the time profile of the detected neutrinos for especially significant events. The mechanism of generation and distribution of alerts, as well as the integration into the SNEWS and SNEWS 2.0 global alert systems, are described. The approach for the follow-up of external alerts with a search for a neutrino excess in the archival data is defined. Finally, an overview of the current detector capabilities and a report after the first two years of operation are given.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A
bstract
KM3NeT/ORCA is a next-generation neutrino telescope optimised for atmospheric neutrino oscillations studies. In this paper, the sensitivity of ORCA to the presence of a light sterile ...neutrino in a 3+1 model is presented. After three years of data taking, ORCA will be able to probe the active-sterile mixing angles
θ
14
,
θ
24
,
θ
34
and the effective angle
θ
μe
, over a broad range of mass squared difference
∆
m
41
2
∼ 10
−
5
,
10 eV
2
, allowing to test the eV-mass sterile neutrino hypothesis as the origin of short baseline anomalies, as well as probing the hypothesis of a very light sterile neutrino, not yet constrained by cosmology. ORCA will be able to explore a relevant fraction of the parameter space not yet reached by present measurements.
The KM3NeT multi-PMT optical module Alshamsi, M.; Alves Garre, S.; Aly, Z. ...
Journal of instrumentation,
07/2022, Letnik:
17, Številka:
7
Journal Article
Recenzirano
Odprti dostop
Abstract
The optical module of the KM3NeT neutrino telescope is an
innovative multi-faceted large area photodetection module. It
contains 31 three-inch photomultiplier tubes in a single 0.44 m
...diameter pressure-resistant glass sphere. The module is a sensory
device also comprising calibration instruments and electronics for
power, readout and data acquisition. It is capped with a
breakout-box with electronics for connection to an electro-optical
cable for power and long-distance communication to the onshore
control station. The design of the module was qualified for the
first time in the deep sea in 2013. Since then, the technology has
been further improved to meet requirements of scalability,
cost-effectiveness and high reliability. The module features a
sub-nanosecond timing accuracy and a dynamic range allowing the
measurement of a single photon up to a cascade of thousands of
photons, suited for the measurement of the Cherenkov radiation
induced in water by secondary particles from interactions of
neutrinos with energies in the range of GeV to PeV. A distributed
production model has been implemented for the delivery of more than
6000 modules in the coming few years with an average production rate
of more than 100 modules per month. In this paper a review is
presented of the design of the multi-PMT KM3NeT optical module with
a proven effective background suppression and signal recognition and
sensitivity to the incoming direction of photons.
This article reports the first observation of the Moon and the Sun shadows in the sky distribution of cosmic-ray induced muons measured by the KM3NeT/ORCA detector. The analysed data-taking period ...spans from February 2020 to November 2021, when the detector had 6 Detection Units deployed at the bottom of the Mediterranean Sea, each composed of 18 Digital Optical Modules. The shadows induced by the Moon and the Sun were detected at their nominal position with a statistical significance of 4.2
σ
and 6.2
σ
, and an angular resolution of
σ
res
=
0
.
49
∘
and
σ
res
=
0
.
66
∘
, respectively, consistent with the prediction of
0
.
53
∘
from simulations. This early result confirms the effectiveness of the detector calibration, in time, position and orientation and the accuracy of the event direction reconstruction. This also demonstrates the performance and the competitiveness of the detector in terms of pointing accuracy and angular resolution.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A
bstract
This article presents the potential of a combined analysis of the JUNO and KM3NeT/ORCA experiments to determine the neutrino mass ordering. This combination is particularly interesting as ...it significantly boosts the potential of either detector, beyond simply adding their neutrino mass ordering sensitivities, by removing a degeneracy in the determination of ∆
m
31
2
between the two experiments when assuming the wrong ordering. The study is based on the latest projected performances for JUNO, and on simulation tools using a full Monte Carlo approach to the KM3NeT/ORCA response with a careful assessment of its energy systematics. From this analysis, a 5
σ
determination of the neutrino mass ordering is expected after 6 years of joint data taking for any value of the oscillation parameters. This sensitivity would be achieved after only 2 years of joint data taking assuming the current global best-fit values for those parameters for normal ordering.
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.
Abstract
The optical data transport system of the KM3NeT neutrino
telescope at the bottom of the Mediterranean Sea will provide more
than 6000 optical modules in the detector arrays with a
...point-to-point optical connection to the control stations
onshore. The ARCA and ORCA detectors of KM3NeT are being installed
at a depth of about 3500 m and 2500 m, respectively and their
distance to the control stations is about 100 kilometers and
40 kilometers. In particular, the two detectors are optimised for
the detection of cosmic neutrinos with energies above about 1 TeV
(ARCA) and for the detection of atmospheric neutrinos with energies
in the range 1 GeV–1 TeV (ORCA). The expected maximum data rate
is 200 Mbps per optical module. The implemented optical data
transport system matches the layouts of the networks of
electro-optical cables and junction boxes in the deep sea. For
efficient use of the fibres in the system the technology of Dense
Wavelength Division Multiplexing is applied. The performance of the
optical system in terms of measured bit error rates, optical budget
are presented. The next steps in the implementation of the system
are also discussed.
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