A
bstract
The ANTARES neutrino telescope has an energy threshold of a few tens of GeV. This allows to study the phenomenon of atmospheric muon neutrino disappearance due to neutrino oscillations. In ...a similar way, constraints on the 3+1 neutrino model, which foresees the existence of one sterile neutrino, can be inferred. Using data collected by the ANTARES neutrino telescope from 2007 to 2016, a new measurement of Δ
m
32
2
and
θ
23
has been performed — which is consistent with world best-fit values — and constraints on the 3+1 neutrino model have been derived.
Neutrino telescopes Costantini, H.
Physics of atomic nuclei,
09/2012, Letnik:
75, Številka:
9
Journal Article
Recenzirano
Neutrino astrophysics offers a new possibility to observe our Universe: high-energy neutrinos, produced by the most energetic phenomena in our Galaxy and in the Universe, carry complementary (if not ...exclusive) information about the cosmos: this young discipline extends in fact the conventional astronomy beyond the usual electromagnetic probe. The weak interaction of neutrinos with matter allows them to escape from the core of astrophysical objects and in this sense they represent a complementary messenger with respect to photons. However, their detection on Earth due to the small interaction cross section requires a large target mass. The aim of this article is to review the scientific motivations of the high-energy neutrino astrophysics, the detection principles together with the description of a running apparatus, the experiment ANTARES, the performance of this detector with some results, and the presentation of other neutrino telescope projects.
We analyze 7.3 yr of ANTARES high-energy neutrino and Fermi Large Area Telescope (LAT) γ-ray data in search of cosmic neutrino + γ-ray ( +γ) transient sources or source populations. Our analysis has ...the potential to detect either individual +γ transient sources (durations s), if they exhibit sufficient γ-ray or neutrino multiplicity, or a statistical excess of +γ transients of individually lower multiplicities. Individual high γ-ray multiplicity events could be produced, for example, by a single ANTARES neutrino in coincidence with a LAT-detected γ-ray burst. Treating ANTARES track and cascade event types separately, we establish detection thresholds by Monte Carlo scrambling of the neutrino data, and determine our analysis sensitivity by signal injection against these scrambled data sets. We find our analysis is sensitive to +γ transient populations responsible for >5% of the observed gamma-coincident neutrinos in the track data at 90% confidence. Applying our analysis to the unscrambled data reveals no individual +γ events of high significance; two ANTARES track + Fermi γ-ray events are identified that exceed a once per decade false alarm rate threshold (p = 17%). No evidence for subthreshold +γ source populations is found among the track (p = 39%) or cascade (p = 60%) events. Exploring a possible correlation of high-energy neutrino directions with Fermi γ-ray sky brightness identified in previous work yields no added support for this correlation. While TXS 0506+056, a blazar and variable (nontransient) Fermi γ-ray source, has recently been identified as the first source of high-energy neutrinos, the challenges in reconciling observations of the Fermi γ-ray sky, the IceCube high-energy cosmic neutrinos, and ultrahigh-energy cosmic rays using only blazars suggest a significant contribution by other source populations. Searches for transient sources of high-energy neutrinos thus remain interesting, with the potential for either neutrino clustering or multimessenger coincidence searches to lead to discovery of the first +γ transients.
A
bstract
A search for magnetic monopoles using five years of data recorded with the ANTARES neutrino telescope from January 2008 to December 2012 with a total live time of 1121 days is presented. ...The analysis is carried out in the range
β
> 0.6 of magnetic monopole velocities using a strategy based on run-by-run Monte Carlo simulations. No signal above the background expectation from atmospheric muons and atmospheric neutrinos is observed, and upper limits are set on the magnetic monopole flux ranging from 5.7 × 10
−16
to 1.5 × 10
−18
cm
−2
·s
−1
·sr
−1
.
A novel algorithm to reconstruct neutrino-induced particle showers within the ANTARES neutrino telescope is presented. The method achieves a median angular resolution of
6
∘
for shower energies below ...100 TeV. Applying this algorithm to 6 years of data taken with the ANTARES detector, 8 events with reconstructed shower energies above 10 TeV are observed. This is consistent with the expectation of about 5 events from atmospheric backgrounds, but also compatible with diffuse astrophysical flux measurements by the IceCube collaboration, from which 2–4 additional events are expected. A
90
%
C.L. upper limit on the diffuse astrophysical neutrino flux with a value per neutrino flavour of
E
2
·
Φ
90
%
=
4.9
·
10
-
8
GeV
·
cm
-
2
·
s
-
1
·
sr
-
1
is set, applicable to the energy range from 23 TeV to 7.8 PeV, assuming an unbroken
E
-
2
spectrum and neutrino flavour equipartition at Earth.
Geographic routing strategies used in wireless communication networks require that each transmitting node is aware of its location, the locations of its neighbors, and the destination. With this ...information, the message is routed by choosing intermediate nodes, or relays, which allow the destination to be reached with the maximum possible transmitted information rate and with minimum delay. However, this strategy needs to take into account the uncertainties of the relays locations in order to avoid an important performance degradation of the link, or even a routing failure.
Taking into account the presence of uncertainties in the relays locations, each possible geographic routing strategy is able to recognize a subset of nodes that can be candidates for relays. Furthermore, the transmission range between nodes not only depends on the distance between them, but also the communication channel fading. Based on the effect that these uncertainties have on the link channel capacity, a minimization of a cost function is proposed to decide the next hop relay, which optimizes, in mean, the maximum rate of information transmitted with the minimum number of hops. Using the location statistics, this optimal strategy is applied for both one-hop decisions and two-hops decisions. Working expressions for on-line fast calculations are provided and used for results illustrations.
Advanced LIGO detected a significant gravitational wave signal (GW170104) originating from the coalescence of two black holes during the second observation run on January 4th, 2017. An all-sky ...high-energy neutrino follow-up search has been made using data from the Antares neutrino telescope, including both upgoing and downgoing events in two separate analyses. No neutrino candidates were found within Formula omitted s around the GW event time nor any time clustering of events over an extended time window of Formula omitted months. The non-detection is used to constrain isotropic-equivalent high-energy neutrino emission from GW170104 to less than Formula omitted erg for a Formula omitted spectrum. This constraint is valid in the energy range corresponding to the 5-95% quantiles of the neutrino flux 3.2 TeV; 3.6 PeV, if the GW emitter was below the Antares horizon at the alert time.
The transition between the Main Sequence and the Red Giant Branch in low mass stars is powered by the onset of CNO burning, whose bottleneck is 14N(p, $\gamma)^{15}$O. The LUNA collaboration has ...recently improved the low energy measurements of the cross section of this key reaction. We analyse the impact of the revised reaction rate on the estimate of the Globular Cluster ages, as derived from the turnoff luminosity. We found that the age of the oldest Globular Clusters should be increased by about 0.7-1 Gyr with respect to the current estimates.
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