1,098 research outputs found
Monte Carlo simulation of EAS generated by 10(14) - 10(16) eV protons
Detailed Monte Carlo simulations of extensive air showers to be detected by the Homestake Surface Underground Telescope and other similar detectors located at sea level and mountain altitudes have been performed for 10 to the 14th power to 10 to the 16th power eV primary energies. The results of these Monte Carlo calculations will provide an opportunity to compare the experimental data with different models for the composition and spectra of primaries and for the development of air showers. The results obtained for extensive air showers generated by 10 to the 14th power to 10 to the 16th power eV primary protons are reported
Modelling the impact of atmospheric and terrestrial inputs on the Black Sea coastal dynamics
International audienceThe dynamics on the North Western Shelf area of the Black Sea are examined, with an emphasis on the circulation induced by buoyancy due to the land drained fresh waters and by the interaction with the atmosphere, notably wind stress. A three-dimensional, multi-layer hydrodynamic model is employed with realistic topography and parameterisation of river plume physics. We focus on the seasonal patterns of transport of the river induced low-salinity waters within the Coastal Low Salinity Band and the conditions that influence their removal toward the shelf interior. The numerical simulations show that coastal circulation is greatly influenced by river runoff and especially in the case of the Danube, which is excessively high with monthly aver-aged values ranging from 5000 to 10000 m3 /s. A significant contribution of runoff comes from the neighbouring rivers. At the same time, the North Western Shelf is quite broad, so that the coastal dynamics are largely sheltered from the conditions in the deeper sea. Buoyancy due to river runoff thus dominates, creating a southward coastal current that is the predominant pathway for the land-drained inputs. As in all shelf areas, wind stress is a major circulation forcing mechanism and it modifies the buoyancy induced flow. It is shown that the seasonal variability in river runoff and wind stress, in combination with the shelf topography, determines the different pathways for the terrestrial inputs. Implications on the overall basin circulation are drawn, as the availability of low-salinity waters of river origin affects the upper Black Sea layer. Consequently, the formation of distinct water masses (such as the Cold Intermediate Layer) and the properties of the outflow toward the Mediterranean are also influenced
Proximity fingerprint of s+- superconductivity
We suggest a straightforward and unambiguous test to identify possible
opposite signs of superconducting order parameter in different bands proposed
for iron-based superconductors (s+- state). We consider proximity effect in a
weakly coupled sandwich composed of a s+- superconductor and thin layer of
s-wave superconductor. In such system the s-wave order parameter is coupled
differently with different s+- gaps and it typically aligns with one of these
gaps. This forces the other s+- gap to be anti-aligned with the s-wave gap. In
such situation the aligned band induces a peak in the s-wave density of states
(DoS), while the anti-aligned band induces a dip. Observation of such
contact-induced negative feature in the s-wave DoS would provide a definite
proof for s+- superconductivity.Comment: 4 pages, one figur
Effects of the galactic magnetic field upon large scale anisotropies of extragalactic Cosmic Rays
The large scale pattern in the arrival directions of extragalactic cosmic
rays that reach the Earth is different from that of the flux arriving to the
halo of the Galaxy as a result of the propagation through the galactic magnetic
field. Two different effects are relevant in this process: deflections of
trajectories and (de)acceleration by the electric field component due to the
galactic rotation. The deflection of the cosmic ray trajectories makes the flux
intensity arriving to the halo from some direction to appear reaching the Earth
from another direction. This applies to any intrinsic anisotropy in the
extragalactic distribution or, even in the absence of intrinsic anisotropies,
to the dipolar Compton-Getting anisotropy induced when the observer is moving
with respect to the cosmic rays rest frame. For an observer moving with the
solar system, cosmic rays traveling through far away regions of the Galaxy also
experience an electric force coming from the relative motion (due to the
rotation of the Galaxy) of the local system in which the field can be
considered as being purely magnetic. This produces small changes in the
particles momentum that can originate large scale anisotropies even for an
isotropic extragalactic flux.Comment: 11 pages, 4 figure
The nature of the highest energy cosmic rays
Ultra high energy gamma rays produce electron--positron pairs in interactions
on the geomagnetic field. The pair electrons suffer magnetic bremsstrahlung and
the energy of the primary gamma ray is shared by a bunch of lower energy
secondaries. These processes reflect the structure of the geomagnetic field and
cause experimentally observable effects. The study of these effects with future
giant air shower arrays can identify the nature of the highest energy cosmic
rays as either gamma-rays or nuclei.Comment: 15 pages of RevTeX plus 6 postscript figures, tarred, gzipped and
uuencoded. Subm. to Physical Review
The energy production rate & the generation spectrum of UHECRs
We derive simple analytic expressions for the flux and spectrum of ultra-high
energy cosmic-rays (UHECRs) predicted in models where the CRs are protons
produced by extra-Galactic sources. For a power-law scaling of the CR
production rate with redshift and energy, d\dot{n} /dE\propto E^-\alpha
(1+z)^m, our results are accurate at high energy, E>10^18.7 eV, to better than
15%, providing a simple and straightforward method for inferring d\dot{n}/dE
from the observed flux at E. We show that current measurements of the UHECR
spectrum, including the latest Auger data, imply
E^2d\dot{n}/dE(z=0)=(0.45\pm0.15)(\alpha-1) 10^44 erg Mpc^-3 yr^-1 at E<10^19.5
eV with \alpha roughly confined to 2\lesseq\alpha<2.7. The uncertainty is
dominated by the systematic and statistic errors in the experimental
determination of individual CR event energy, (\Delta E/E)_{sys} (\Delta
E/E)_{stat} ~20%. At lower energy, d\dot{n}/dE is uncertain due to the unknown
Galactic contribution. Simple models in which \alpha\simeq 2 and the transition
from Galactic to extra-Galactic sources takes place at the "ankle", E ~10^19
eV, are consistent with the data. Models in which the transition occurs at
lower energies require a high degree of fine tuning and a steep spectrum,
\alpha\simeq 2.7, which is disfavored by the data. We point out that in the
absence of accurate composition measurements, the (all particle) energy
spectrum alone cannot be used to infer the detailed spectral shapes of the
Galactic and extra-Galactic contributions.Comment: 9 pages, 11 figures, minor revision
New results in the deformed N=4 SYM theory
We investigate various perturbative properties of the deformed N=4 SYM
theory. We carry out a three-loops calculation of the chiral matter superfield
propagator and derive the condition on the couplings for maintaining finiteness
at this order. We compute the 2-, 3- and 4-point functions of composite
operators of dimension 2 at two loops. We identify all the scalar operators
(chiral and non-chiral) of bare dimension 4 with vanishing one-loop anomalous
dimension. We compute some 2- and 3-point functions of these operators at two
loops and argue that the observed finite corrections cannot be absorbed by a
finite renormalization of the operators.Comment: LaTeX, 16 pages, 1 figure; references added; typos corrected; final
version to appear in Nucl. Phys.
Charged Higgs boson contribution to for very large in the two Higgs doublet model with UHE-neutrinos
We study the deep inelastic process
(with an isoscalar nucleon), in the context of the
two Higgs doublet model {\it type two} (2HDM(II)). In particular, we discuss
the contribution to the total cross section of diagrams, in which a charged
Higgs boson is exchanged. We show that for large values of such
contribution for an inclusive dispersion generated through the collision of an
ultrahigh energy tau-neutrino on a target nucleon can reach up to 57% of the
value of the contribution of the exchange diagrams (i.e. can reach up to
57% of the standard model (SM) prediction) and could permit to distinguish
between the SM and the 2HDM(II) predictions at the Pierre Auger Observatory.Comment: 10 pages, 5 figure
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