20 research outputs found
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
Structure Formation with Mirror Dark Matter: CMB and LSS
In the mirror world hypothesis the mirror baryonic component emerges as a
possible dark matter candidate. An immediate question arises: how the mirror
baryons behave and what are the differences from the more familiar dark matter
candidates as e.g. cold dark matter? In this paper we answer quantitatively to
this question. First we discuss the dependence of the relevant scales for the
structure formation (Jeans and Silk scales) on the two macroscopic parameters
necessary to define the model: the temperature of the mirror plasma (limited by
the Big Bang Nucleosynthesis) and the amount of mirror baryonic matter. Then we
perform a complete quantitative calculation of the implications of mirror dark
matter on the cosmic microwave background and large scale structure power
spectrum. Finally, confronting with the present observational data, we obtain
some bounds on the mirror parameter space.Comment: 11 pages, 6 figures; minor corrections, references added; accepted
for publication in IJMP
Unveiling the nature of galactic TeV sources with IceCube results
IceCube collaboration reported the first high-significance observation of the
neutrino emission from the Galactic disk. The observed signal can be due to
diffuse emission produced by cosmic rays interacting with interstellar gas but
can also arise from a population of sources. In this paper, we evaluate both
the diffuse and source contribution by taking advantage of gamma-ray
observations and/or theoretical considerations. By comparing our expectations
with IceCube measurement, we constrain the fraction of Galactic TeV gamma-ray
sources (resolved and unresolved) with hadronic nature. In order to be
compatible with the IceCube results, this fraction should be less than corresponding to a cumulative source flux integrated in the 1-100 TeV energy range
Setting an upper limit for the total TeV neutrino flux from the disk of our Galaxy
We set an upper limit for the total TeV neutrino flux expected from the disk
of our Galaxy in the region and probed by the
ANTARES experiment. We include both the diffuse emission, due to the
interaction of cosmic rays with the interstellar medium, and the possible
contribution produced by gamma-ray Galactic sources. The neutrino diffuse
emission is calculated under different assumptions for the cosmic ray spatial
and energy distribution in our Galaxy. In particular, we assume that the total
gamma-ray flux produced by all the sources, resolved and unresolved by
H.E.S.S., is produced via hadronic interaction and, hence, is coupled with
neutrino emission. We compare our total neutrino flux with the recent ANTARES
measurement of the neutrino from the Galactic Ridge. We show that the ANTARES
best-fit flux requires the existence of a large source component, close to or
even larger than the most optimistic predictions obtained with our approach
New axion and hidden photon constraints from a solar data global fit
We present a new statistical analysis that combines helioseismology (sound
speed, surface helium and convective radius) and solar neutrino observations
(the B and Be fluxes) to place upper limits to the properties of non
standard weakly interacting particles. Our analysis includes theoretical and
observational errors, accounts for tensions between input parameters of solar
models and can be easily extended to include other observational constraints.
We present two applications to test the method: the well studied case of axions
and axion-like particles and the more novel case of low mass hidden photons.
For axions we obtain an upper limit at for the axion-photon coupling
constant of . For hidden
photons we obtain the most restrictive upper limit available accross a wide
range of masses for the product of the kinetic mixing and mass of at . Both cases improve the previous solar
constraints based on the Standard Solar Models showing the power of using a
global statistical approach.Comment: 23 pages, 12 figure
Helioseismic and neutrino data-driven reconstruction of solar properties
In this work, we use Bayesian inference to quantitatively reconstruct the solar properties most relevant to the solar composition problem using as inputs the information provided by helioseismic and solar neutrino data. In particular, we use a Gaussian process to model the functional shape of the opacity uncertainty to gain flexibility and become as free as possible from prejudice in this regard. With these tools we first readdress the statistical significance of the solar composition problem. Furthermore, starting from a composition unbiased set of standard solar models (SSMs) we are able to statistically select those with solar chemical composition and other solar inputs which better describe the helioseismic and neutrino observations. In particular, we are able to reconstruct the solar opacity profile in a data-driven fashion, independently of any reference opacity tables, obtaining a 4 per cent uncertainty at the base of the convective envelope and 0.8 per cent at the solar core. When systematic uncertainties are included, results are 7.5 per cent and 2 per cent, respectively. In addition, we find that the values of most of the other inputs of the SSMs required to better describe the helioseismic and neutrino data are in good agreement with those adopted as the standard priors, with the exception of the astrophysical factor S11 and the microscopic diffusion rates, for which data suggests a 1 per cent and 30 per cent reduction, respectively. As an output of the study we derive the corresponding data-driven predictions for the solar neutrino fluxes
Atmospheric neutrino flux supported by recent muon experiments
We present a new one-dimensional calculation of low and intermediate energy
atmospheric muon and neutrino fluxes, using up-to-date data on primary cosmic
rays and hadronic interactions. We study several sources of uncertainties
relevant to our calculations. A comparison with the muon fluxes and charge
ratios measured in several modern balloon-borne experiments suggests that the
atmospheric neutrino flux is essentially lower than one used for the standard
analyses of the sub-GeV and multi-GeV neutrino induced events in underground
detectors.Comment: 23 pages, 7 figures, 2 tables. Typos corrected, figure layout
improved, references added. Final version accepted for publication in PL