536 research outputs found
The influence of the geomagnetic field and of the uncertainties in the primary spectrum on the development of the muon flux in the atmosphere
In this paper we study the sensitivity of the flux of atmospheric muons to
uncertainties in the primary cosmic ray spectrum and to the treatment of the
geomagnetic field in a calculation. We use the air shower simulation program
AIRES to make the calculation for two different primary spectra and under
several approximations to the propagation of charged particles in the
geomagnetic field. The results illustrate the importance of accurate modelling
of the geomagnetic field effects. We propose a high and a low fit of the proton
and helium fluxes, and calculate the muon fluxes with these different inputs.
Comparison with measurements of the muon flux by the CAPRICE experiment shows a
slight preference for the higher primary cosmic ray flux parametrization.Comment: 24 pages, 13 figures, submitted to Phys.Rev.
Fluctuations of Xmax and Primary Particle Mass Composition in the Range of Energy 5 10^{17} - 3 10^{19} ev by Yakutsk Data
The experimental distributions of \Xmax obtained with the Yakutsk EAS array
at fixed energies of , and
eV are analysed. A recent version of the QGSJET model is used as a tool of our
analysis. In the framework of this model, the most adequate mass composition of
primary particles satisfying the experimental data on \Xmax is selected.Comment: 19th European Cosmic Ray Symposium, Aug 30 - Sep 3 2004, Florence,
Italy. 3 pages, 1 figure. Submitted for publication in International Journal
of Modern Physics
Hunting long-lived gluinos at the Pierre Auger Observatory
Eventual signals of split sypersymmetry in cosmic ray physics are analyzed in
detail. The study focusses particularly on quasi-stable colorless R-hadrons
originating through confinement of long-lived gluinos (with quarks,
anti-quarks, and gluons) produced in pp collisions at astrophysical sources.
Because of parton density requirements, the gluino has a momentum which is
considerable smaller than the energy of the primary proton, and so production
of heavy (mass ~ 500 GeV) R-hadrons requires powerful cosmic ray engines able
to accelerate particles up to extreme energies, somewhat above 10^{13.6} GeV.
Using a realistic Monte Carlo simulation with the AIRES engine, we study the
main characteristics of the air showers triggered when one of these exotic
hadrons impinges on a stationary nucleon of the Earth atmosphere. We show that
R-hadron air showers present clear differences with respect to those initiated
by standard particles. We use this shower characteristics to construct
observables which may be used to distinguish long-lived gluinos at the Pierre
Auger Observatory.Comment: 13 pages revtex, 9 eps figures. A ps version with high resolution
figures is available at
http://www.hep.physics.neu.edu/staff/doqui/rhadron_highres.p
Computationally efficient methods for modelling laser wakefield acceleration in the blowout regime
Electron self-injection and acceleration until dephasing in the blowout
regime is studied for a set of initial conditions typical of recent experiments
with 100 terawatt-class lasers. Two different approaches to computationally
efficient, fully explicit, three-dimensional particle-in-cell modelling are
examined. First, the Cartesian code VORPAL using a perfect-dispersion
electromagnetic solver precisely describes the laser pulse and bubble dynamics,
taking advantage of coarser resolution in the propagation direction, with a
proportionally larger time step. Using third-order splines for macroparticles
helps suppress the sampling noise while keeping the usage of computational
resources modest. The second way to reduce the simulation load is using
reduced-geometry codes. In our case, the quasi-cylindrical code CALDER-CIRC
uses decomposition of fields and currents into a set of poloidal modes, while
the macroparticles move in the Cartesian 3D space. Cylindrical symmetry of the
interaction allows using just two modes, reducing the computational load to
roughly that of a planar Cartesian simulation while preserving the 3D nature of
the interaction. This significant economy of resources allows using fine
resolution in the direction of propagation and a small time step, making
numerical dispersion vanishingly small, together with a large number of
particles per cell, enabling good particle statistics. Quantitative agreement
of the two simulations indicates that they are free of numerical artefacts.
Both approaches thus retrieve physically correct evolution of the plasma
bubble, recovering the intrinsic connection of electron self-injection to the
nonlinear optical evolution of the driver
On the angular distribution of extensive air showers
Angular distributions of extensive air showers with different number of
charged particles in the range 2.5x10^5--4x10^7 are derived using the
experimental data obtained with the EAS MSU array. Possible approximations of
the obtained distributions with different empiric functions available in
literature, are analysed. It is shown that the exponential function provides
the best approximation of the angular distributions in the sense of the
chi-squared criterion.Comment: 5 pages including 1 figur
New personalized genetic mouse model of Lesch-Nyhan syndrome for pharmacology and gene therapy
In the current study, we present the results of the generation of a genetically modified mouse strain carrying a deletion in the HPRT1 gene. These mice can be effectively used for the preclinical testing of new drugs aimed at the treatment of Lesch-Nyhan syndrom
Possibility of Using a Satellite-Based Detector for Recording Cherenkov Light from Ultrahigh-Energy Extensive Air Showers Penetrating into the Ocean Water
We have estimated the reflected component of Cherenkov radiation, which
arises in developing of an extensive air shower with primary energy of 10^20 eV
over the ocean surface. It has been shown that, under conditions of the TUS
experiment, a flash of the reflected Cherenkov photons at the end of the
fluorescence track can be identified in showers with zenith angles up to 20
degrees.Comment: 5 pages, 3 figures. This preprint corrects errors which appeared in
the English version of the article published in Bull. Rus. Acad. Sci. Phys.,
2011, Vol. 75, No. 3, p. 381. The original russian text was published in Izv.
RAN. Ser. Fiz., 2011, Vol. 75, No. 3, p. 41
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