9 research outputs found
High energy neutrino yields from astrophysical sources I: Weakly magnetized sources
We calculate the yield of high energy neutrinos produced in astrophysical
sources with negligible magnetic fields varying their interaction depth from
nearly transparent to opaque. We take into account the scattering of
secondaries on background photons as well as the direct production of neutrinos
in decays of charm mesons. If multiple scattering of nucleons becomes
important, the neutrino spectra from meson and muon decays are strongly
modified with respect to transparent sources. Characteristic for neutrino
sources containing photons as scattering targets is a strong energy-dependence
of the ratio of and fluxes at the sources, ranging from
below threshold to close to the energy
where the decay length of charged pions and kaons equals their interaction
length on target photons. Above this energy, the neutrino flux is strongly
suppressed and depends mainly on charm production.Comment: 10 pages, 16 figures, references added, matches published versio
High energy neutrino yields from astrophysical sources II: Magnetized sources
We calculate the yield of high energy neutrinos produced in astrophysical
sources for arbitrary interaction depths and magnetic field strengths
. We take into account energy loss processes like synchrotron radiation and
diffusion of charged particles in turbulent magnetic fields as well as the
scattering of secondaries on background photons and the direct production of
charm neutrinos. Meson-photon interactions are simulated with an extended
version of the SOPHIA model. Diffusion leads to an increased path-length before
protons leave the source of size R_s and therefore magnetized sources lose
their transparency below the energy , with and 1 for Kolmogorov and
Bohm diffusion, respectively. Moreover, the neutrino flux is suppressed above
the energy where synchrotron energy losses become important for charged
particles. As a consequence, the energy spectrum and the flavor composition of
neutrinos are strongly modified both at low and high energies even for sources
with \tau_0\lsim 1.Comment: 15 pages, 16 figure
Restricting UHECRs and cosmogenic neutrinos with Fermi-LAT
Ultrahigh energy cosmic ray (UHECR) protons interacting with the cosmic
microwave background (CMB) produce UHE electrons and gamma-rays that in turn
initiate electromagnetic cascades on CMB and infrared photons. As a result, a
background of diffuse isotropic gamma radiation is accumulated in the energy
range E\lsim 100 GeV. The Fermi-LAT collaboration has recently reported a
measurement of the extragalactic diffuse background finding it less intense and
softer than previously measured by EGRET. We show that this new result
constrains UHECR models and the flux of cosmogenic neutrinos. In particular, it
excludes models with cosmogenic neutrino fluxes detectable by existing neutrino
experiments, while next-generation detectors as e.g. JEM-EUSO can observe
neutrinos only for extreme parameters.Comment: 7 pages, 6 eps figures; v2: minor changes, v3: final version, added
discussion of EGMF influenc
Black Holes from Cosmic Rays: Probes of Extra Dimensions and New Limits on TeV-Scale Gravity
If extra spacetime dimensions and low-scale gravity exist, black holes will
be produced in observable collisions of elementary particles. For the next
several years, ultra-high energy cosmic rays provide the most promising window
on this phenomenon. In particular, cosmic neutrinos can produce black holes
deep in the Earth's atmosphere, leading to quasi-horizontal giant air showers.
We determine the sensitivity of cosmic ray detectors to black hole production
and compare the results to other probes of extra dimensions. With n \ge 4 extra
dimensions, current bounds on deeply penetrating showers from AGASA already
provide the most stringent bound on low-scale gravity, requiring a fundamental
Planck scale M_D > 1.3 - 1.8 TeV. The Auger Observatory will probe M_D as large
as 4 TeV and may observe on the order of a hundred black holes in 5 years. We
also consider the implications of angular momentum and possible exponentially
suppressed parton cross sections; including these effects, large black hole
rates are still possible. Finally, we demonstrate that even if only a few black
hole events are observed, a standard model interpretation may be excluded by
comparison with Earth-skimming neutrino rates.Comment: 30 pages, 18 figures; v2: discussion of gravitational infall, AGASA
and Fly's Eye comparison added; v3: Earth-skimming results modified and
strengthened, published versio
Ultra-High Energy Neutrino Fluxes and Their Constraints
Applying our recently developed propagation code we review extragalactic
neutrino fluxes above 10^{14} eV in various scenarios and how they are
constrained by current data. We specifically identify scenarios in which the
cosmogenic neutrino flux, produced by pion production of ultra high energy
cosmic rays outside their sources, is considerably higher than the
"Waxman-Bahcall bound". This is easy to achieve for sources with hard injection
spectra and luminosities that were higher in the past. Such fluxes would
significantly increase the chances to detect ultra-high energy neutrinos with
experiments currently under construction or in the proposal stage.Comment: 11 pages, 15 figures, version published in Phys.Rev.
Effects of charged Higgs bosons in the deep inelastic process \nu_{\tau} {\cal N} \to \tau^- X and the possibility of detecting tau-neutrinos at cosmic neutrino detectors
We study the deep inelastic process
(with an isoscalar nucleon), in the context of the
two Higgs doublet model type II (2HDM(II)). We discuss the contribution to the
total cross section of diagrams, in which a charged Higgs boson is exchanged.
We present results which show the strong dependence of such contribution on
and . We show that in the region and 90 GeV 600 GeV with the additional
experimental constraint on the involved model parameters GeV, the contribution of the charged Higgs boson exchange
diagrams to the cross section of the charged current inclusive collision can become important. We obtain that this contribution for
an inclusive dispersion generated through the collision of an ultrahigh energy
tau-neutrino with eV on a target nucleon can be
larger than the value of the contribution of the exchange diagrams,
provided that GeV and . Such
enhancement and the induced variation on the mean inelasticity
could lead to sizeable effects in the acceptance of cosmic tau-neutrino
detectors at experiments such as HiRes, PAO, and the CRTNT, which are anchored
to the ground, and at experiments such as EUSO and OWL, which are proposed to
orbit around the Earth.Comment: 18 pages, 2 figures, 8 table