The detection of very high-energy neutrinos by IceCube experiment supports the existence of a comparable gamma-ray counterpart from the same cosmic accelerators. Under the likely assumption that the ...sources of these particles are of extragalactic origin, the emitted photon flux would be significantly absorbed during its propagation over cosmic distances. However, in the presence of photon mixing with ultra-light axion-like-particles (ALPs), this expectation would be strongly modified. Notably, photon-ALP conversions in the host galaxy would produce an ALP flux which propagates unimpeded in the extragalactic space. Then, the back-conversion of ALPs in the Galactic magnetic field leads to a diffuse high-energy photon flux. In this context, the recent detection of the diffuse high-energy photon flux by the Large High Altitude Air Shower Observatory (LHAASO) allows us to exclude at the
95
%
CL an ALP-photon coupling
g
a
γ
≳
3.9
–
7.8
×
10
-
11
GeV
-
1
for
m
a
≲
4
×
10
-
7
eV
, depending on the assumptions on the magnetic fields and on the original gamma-ray spectrum. This new bound is complementary with other ALP constraints from very-high-energy gamma-ray experiments and sensitivities of future experiments.
Abstract
The recent discovery of astrophysical neutrinos from the Seyfert galaxy NGC 1068 suggests the presence of nonthermal protons within a compact “coronal” region close to the central black ...hole. The acceleration mechanism of these nonthermal protons remains elusive. We show that a large-scale magnetic reconnection layer, of the order of a few gravitational radii, may provide such a mechanism. In such a scenario, rough energy equipartition between magnetic fields, X-ray photons, and nonthermal protons is established in the reconnection region. Motivated by recent 3D particle-in-cell simulations of relativistic reconnection, we assume that the spectrum of accelerated protons is a broken power law, with the break energy being constrained by energy conservation (i.e., the energy density of accelerated protons is at most comparable to the magnetic energy density). The proton spectrum is
dn
p
/
dE
p
∝
E
p
−
1
below the break and
dn
p
/
dE
p
∝
E
p
−
s
above the break, with IceCube neutrino observations suggesting
s
≃ 3. Protons above the break lose most of their energy within the reconnection layer via photohadronic collisions with the coronal X-rays, producing a neutrino signal in good agreement with the recent observations. Gamma rays injected in photohadronic collisions are cascaded to lower energies, sustaining the population of electron–positron pairs that makes the corona moderately Compton thick.
The origin of high-energy cosmic rays, and their behavior in astrophysical sources, remains an open question. Recently, new ways to address this question have been made possible by the observation of ...a new astrophysical messenger, namely neutrinos. The IceCube telescope has detected a diffuse flux of astrophysical neutrinos in the TeV-PeV energy range, likely produced in astrophysical sources accelerating cosmic rays, and more recently it has reported on a few candidate individual neutrino sources. Future experiments will be able to improve on these measurements quantitatively, by the detection of more events, and qualitatively, by extending the measurement into the EeV energy range. In this paper, we review the main features of the neutrino emission and sources observed by IceCube, as well as the main candidate sources that could contribute to the diffuse neutrino flux. As a parallel question, we review the status of high-energy neutrinos as a probe of Beyond the Standard Model physics coupling to the neutrino sector.
Vaccinations may induce cutaneous adverse events, due to nonspecific inflammation or immuno-mediated reactions. Several types of vasculitis have been observed. We report on a 71-year-old woman who ...developed cutaneous small-vessel vasculitis after the second dose of Vaxzevria COVID-19 vaccination, showing leukocytoclastic vasculitis on histopathological examination of a skin biopsy.
Cutaneous small-vessel vasculitis is a rare condition which can be idiopathic or secondary to underlying infections, connective tissue disorders, malignancy, and medications. The pathogenesis involves immune complex deposition in small blood vessels, leading to activation of the complement system and recruitment of leukocytes.
Exacerbation of small-vessel vasculitis has been reported following the administration of various vaccines, particularly influenza vaccine. It is expected that SARS-CoV-2 vaccine results in the activation of B- and T-cells and antibody formation. We hypothesize that leukocytoclastic vasculitis caused by immune complex deposition within cutaneous small vessels could be a rare side effect of Vaxzevria COVID‐19 vaccination.
•Vasculitis precipitation has been reported secondary to different vaccines.•A 71-year-old woman developed cutaneous vasculitis after receiving COVID-19 vaccine.•COVID-19 vaccine might result in immune complex deposition within small vessels.•Leukocytoclastic vasculitis might be an adverse reaction to COVID-19 vaccination.
Majoron-like bosons would emerge from a supernova (SN) core by neutrino coalescence of the form νν→ϕ and νover ¯νover ¯→ϕ with 100-MeV-range energies. Subsequent decays to (anti)neutrinos of all ...flavors provide a flux component with energies much larger than the usual flux from the "neutrino sphere." The absence of 100-MeV-range events in the Kamiokande-II and Irvine-Michigan-Brookhaven signal of SN 1987A implies that less than 1% of the total energy was thus emitted and provides the strongest constraint on the Majoron-neutrino coupling of g≲10^{-9} MeV/m_{ϕ} for 100 eV≲m_{ϕ}≲100 MeV. It is straightforward to extend our new argument to other hypothetical feebly interacting particles.
Neutrino phenomenology from leptogenesis Buccella, Franco; Fiorillo, Damiano F. G.; Miele, Gennaro ...
The European physical journal. C, Particles and fields,
10/2018, Letnik:
78, Številka:
10
Journal Article
Recenzirano
Odprti dostop
Assuming a type-I seesaw mechanism for neutrino mass generation and invoking a baryogenesis
via
leptogenesis scenario, we consider a reasonable hierarchical structure for Dirac neutrino mass matrix, ...similar to up-type quark mass matrix. These hypotheses imply a relevant connection between high scale CP violation and low energy one. By requiring a compact heavy neutrino mass spectrum, which allows to circumvent Davidson–Ibarra limit, one can obtain an efficient leptogenesis restricting the allowed region for low energy neutrino parameters. Once the oscillating parameters are taken inside a
3
σ
range, through the numerical resolution of the leptogenesis Boltzmann equations one gets the following allowed intervals for the lightest neutrino mass and the Dirac CP phase:
-
0.90
π
<
δ
<
-
0.75
π
and
m
1
∼
(
0.002
-
0.004
)
eV.
When hypothetical neutrino secret interactions (νSI) are large, they form a fluid in a supernova (SN) core, flow out with sonic speed, and stream away as a fireball. For the first time, we tackle the ...complete dynamical problem and solve all steps, systematically using relativistic hydrodynamics. The impact on SN physics and the neutrino signal is remarkably small. For complete thermalization within the fireball, the observable spectrum changes in a way that is independent of the coupling strength. One potentially large effect beyond our study is quick deleptonization if νSI violate lepton number. By present evidence, however, SN physics leaves open a large region in parameter space, where laboratory searches and future high-energy neutrino telescopes will probe νSI.
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