2,121 research outputs found
The flavor composition of astrophysical neutrinos after 8 years of IceCube: an indication of neutron decay scenario?
In this work we present an updated study of the flavor composition suggested
by astrophysical neutrinos observed by IceCube. The main novelties compared to
previous studies are the following: 1) we use the most recent measurements,
namely 8 years of throughgoing muons and 7.5 years of High Energy Starting
Events (HESE); 2) we consider a broken power law spectrum, in order to be
consistent with the observations between 30 TeV and few PeV; 3) we use the
throughgoing muon flux to predict the number of astrophysical HESE tracks. We
show that accounting for the three previous elements, the result favors
surprisingly the hypothesis of neutrinos produced by neutron decay, disfavoring
the standard picture of neutrinos from pion decay at 2.0 and the damped
muons regime at , once the atmospheric background is considered.
Although the conventional scenario is not yet completely ruled out in the
statistically and alternative interpretations are also plausible, such as an
energy spectrum characterized by a non trivial shape, this intriguing result
may suggest new directions for both theoretical interpretation and experimental
search strategies.Comment: 8 pages, 5 figures. Published on EPJ
A multi-component model for the IceCube neutrino events
The IceCube neutrino telescope has observed for the first time a diffuse flux
of high energy neutrinos, with a possible astrophysical origin. Up to now there
are no evidence of sources and many hypothesis are still plausible in order to
explain the measured flux. In this proceeding we analyze an alternative way to
interpret the IceCube neutrinos, in terms of sum of contributions from
different sources.Comment: Prepared for the proceeding of the conference IFAE 201
Can BL Lac emission explain the neutrinos above 0.2 PeV?
Multi-messenger astronomy can help to investigate the sources of the
high-energy neutrinos observed by the high-energy neutrino telescope IceCube.
We consider the hypothesis that the highest energy neutrinos are produced by BL
Lacs, arguing that this is not contradicted severely by any known fact. We
check the BL Lac hypothesis by searching for correlations between the
through-going muon events of IceCube and the BL Lacs of the second catalog of
Fermi-LAT (2FHL). We expect 10.2 2.4 correlated events but we find that
just 1 event has a BL Lac as counterpart. We also assess the probability of
observing one multiplet from the same source, finding that the present null
result is not yet of critical significance. We conclude that the hypothesis
that the BL Lacs are the main emitters of the highest-energy neutrinos observed
by IceCube is disfavored at 3.7{\sigma}. We discuss implications and possible
ways out; for example, this could work if the angular resolution was 4{\deg},
which is much more than expected.Comment: 10 pages, 6 figures. Accepted for publication in Astronomy &
Astrophysic
The natural parametrization of cosmic neutrino oscillations
The natural parameterization of vacuum oscillations in three neutrino flavors
is studied. Compact and exact relations of its three parameters with the
ordinary three mixing angles and CP violating phase are obtained. Its
usefulness is illustrated by considering various applications: the study of the
flavor ratio and of its uncertainties, the comparison of expectations and
observations in the flavor triangle, the intensity of the signal due to Glashow
resonance. The results in the literature are easily reproduced and in
particular the recently obtained agreement of the observations of IceCube with
the hypothesis of cosmic neutrino oscillations is confirmed. It is argued that
a Gaussian treatment of the errors appropriately describes the effects of the
uncertainties on neutrino oscillation parameters.Comment: 19 pages, 5 figures. Text and bibliography enhanced, results
unchanged. New analysis on flavor triangle included. Accepted for publication
in EPJ
Introduction to neutrino astronomy
This writeup is an introduction to neutrino astronomy, addressed to
astronomers and written by astroparticle physicists. While the focus is on
achievements and goals in neutrino astronomy, rather than on the aspects
connected to particle physics, we will introduce the particle physics concepts
needed to appreciate those aspects that depend on the peculiarity of the
neutrinos. The detailed layout is as follows: In Sect.~1, we introduce the
neutrinos, examine their interactions, and present neutrino detectors and
telescopes. In Sect.~2, we discuss solar neutrinos, that have been detected and
are matter of intense (theoretical and experimental) studies. In Sect.~3, we
focus on supernova neutrinos, that inform us on a very dramatic astrophysical
event and can tell us a lot on the phenomenon of gravitational collapse. In
Sect.~4, we discuss the highest energy neutrinos, a very recent and lively
research field. In Sect.~5, we review the phenomenon of neutrino oscillations
and assess its relevance for neutrino astronomy. Finally, we offer a brief
overall assessment and a summary in Sect.~6. The material is selected - i.e.,
not all achievements are reviewed - and furthermore it is kept to an
introductory level, but efforts are made to highlight current research issues.
In order to help the beginner, we prefer to limit the list of references,
opting whenever possible for review works and books.Comment: 15 pages, 5 figures. Accepted for publication The European Physical
Journal Plus. Based on the lecture given at the "4th Azarquiel School of
Astronomy", June 2017, Porto Paolo di Capo Passero, Syracuse (Italy)
https://agenda.infn.it/conferenceDisplay.py?confId=1208
Foreign Investment in Indonesia
The purpose of this Article is to describe the principal laws and regulations currently applicable to foreign investment in Indonesia, including the investment approval process, local incorporation rules, reporting requirements, investment incentives, foreign employee guidelines, investment guaranties, and protection of intellectual property rights
Double pulses and cascades above 2 PeV in IceCube
IceCube collaboration has seen an unexpected population of high energy
neutrinos compatible with an astrophysical origin. We consider two categories
of events that can help to diagnose cosmic neutrinos: double pulse, that may
allow us to clearly discriminate the cosmic component of tau neutrinos;
cascades with deposited energy above 2 PeV, including events produced by
electron antineutrinos at the Glashow resonance, that can be used to
investigate the neutrino production mechanisms. We show that one half of the
double pulse signal is due to the neutrinos spectral region already probed by
IceCube. By normalizing to HESE data, we find that 10 more years are required
to obtain 90% probability to observe a double pulse. The cascades above 2 PeV
provide us a sensitive probe of the high energy tail of the neutrino spectrum
and are potentially observable, but even in this case, the dependence on type
of the source is mild. In fact we find that pp or p{\gamma} mechanisms give a
difference in the number of cascades above 2 PeV of about 25 % that can be
discriminated at 2{\sigma} in about 50 years of data taking.Comment: 20 pages, 7 figures, accepted for publication in EPJ
IceCube Neutrinos from Hadronically Powered Gamma-Ray Galaxies
In this work we use a multi-messenger approach to determine if the high
energy diffuse neutrino flux observed by the IceCube Observatory can originate
from -ray sources powered by Cosmic Rays interactions with gas. Typical
representatives of such sources are Starburst and Ultra-Luminous Infrared
Galaxies. Using the three most recent calculations of the non-blazar
contribution to the extragalactic -ray background measured by the
Fermi-LAT collaboration, we find that a hard power-law spectrum with spectral
index is compatible with all the estimations for the allowed
contribution from non-blazar sources, within 1. Using such a spectrum
we are able to interpret the IceCube results, showing that various classes of
hadronically powered -ray galaxies can provide the dominant
contribution to the astrophysical signal above 100 TeV and about half of the
contribution to the energy flux between 10-100 TeV. With the addition of
neutrinos from the Galactic plane, it is possible to saturate the IceCube
signal at high energy. Our result shows that these sources are still well
motivated candidates.Comment: Accepted for publication on JCA
A Multi-Component Model for the Observed Astrophysical Neutrinos
We propose a multi-component model for the observed diffuse neutrino flux,
including the residual atmospheric backgrounds, a Galactic contribution (such
as from cosmic ray interactions with gas), an extra-galactic contribution from
pp interactions (such as from starburst galaxies) and a hard extragalatic
contribution from photo-hadronic interactions at the highest energies (such as
from Tidal Disruption Events or Active Galactic Nuclei). We demonstrate that
this model can address the key problems of astrophysical neutrino data, such as
the different observed spectral indices in the high-energy starting and
through-going muon samples, a possible anisotropy due to Galactic events, the
non-observation of point sources, and the constraint from the extragalatic
diffuse gamma-ray background. Furthermore, the recently observed muon track
with a deposited energy of 4.5 PeV might be interpreted as evidence for the
extragalactic photo-hadronic contribution. We perform the analysis based on the
observed events instead of the unfolded fluxes by computing the probability
distributions for the event type and reconstructed neutrino energy. As a
consequence, we give the probability to belong to each of these astrophysical
components on an event-to-event basis.Comment: 20 pages, 12 figures. Accepted for publication in A&
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