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تسجيل مستخدم جديدA Multi-Component Measurement of the Cosmic Ray Composition Between 10^{17} eV and 10^{18} eV
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The average mass composition of cosmic rays with primary energies between $10^{17}$eV and $10^{18}$eV has been studied using a hybrid detector consisting of the High Resolution Flys Eye (HiRes) prototype and the MIA muon array. Measurements have been made of the change in the depth of shower maximum, $X_{max}$, and in the change in the muon density at a fixed core location, $rho_mu(600m)$, as a function of energy. The composition has also been evaluated in terms of the combination of $X_{max}$ and $rho_mu(600m)$. The results show that the composition is changing from a heavy to lighter mix as the energy increases.
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We study the spectrum and average mass composition of cosmic rays with primary energies between 10^{17} eV and 10^{18} eV using a hybrid detector consisting of the High Resolution Flys Eye (HiRes) prototype and the MIA muon array. Measurements have b
een made of the change in the depth of shower maximum as a function of energy. A complete Monte Carlo simulation of the detector response and comparisons with shower simulations leads to the conclusion that the cosmic ray intensity is changing f rom a heavier to a lighter composition in this energy range. The spectrum is consistent with earlier Flys Eye measurements and supports the previously found steepening near 4 times 10^{17} eV .
Anisotropy in the arrival directions of cosmic rays with energies above 10$^{17}$eV is studied using data from the Akeno 20 km$^2$ array and the Akeno Giant Air Shower Array (AGASA), using a total of about 117,000 showers observed during 11 years. In
the first harmonic analysis, we have found strong anisotropy of $sim$ 4% around 10$^{18}$eV, corresponding to a chance probability of 0.2%. With two dimensional analysis in right ascension and declination, this anisotropy is interpreted as an excess of showers near the directions of the Galactic Center and the Cygnus region.
Cosmic rays are the highest energy particles found in nature. Measurements of the mass composition of cosmic rays between 10^{17} eV and 10^{18} eV are essential to understand whether this energy range is dominated by Galactic or extragalactic source
s. It has also been proposed that the astrophysical neutrino signal comes from accelerators capable of producing cosmic rays of these energies. Cosmic rays initiate cascades of secondary particles (air showers) in the atmosphere and their masses are inferred from measurements of the atmospheric depth of the shower maximum, Xmax, or the composition of shower particles reaching the ground. Current measurements suffer from either low precision, or a low duty cycle and a high energy threshold. Radio detection of cosmic rays is a rapidly developing technique, suitable for determination of Xmax with a duty cycle of in principle nearly 100%. The radiation is generated by the separation of relativistic charged particles in the geomagnetic field and a negative charge excess in the shower front. Here we report radio measurements of Xmax with a mean precision of 16 g/cm^2 between 10^{17}-10^{17.5} eV. Because of the high resolution in $Xmax we can determine the mass spectrum and find a mixed composition, containing a light mass fraction of ~80%. Unless the extragalactic component becomes significant already below 10^{17.5} eV, our measurements indicate an additional Galactic component dominating at this energy range.
There are some discrepancies in the results on energy spectrum from Yakutsk, AGASA, and HiRes experiments. In this work differential energy spectrum of primary cosmic rays based on the Yakutsk EAS Array data is presented. For the largest events value
s of $S_{600}$ and axes coordinates have been obtained using revised lateral distribution function. Simulation of converters response at large distances showed no considerable underestimation of particle density. Complex shape of spectrum in region of $E > 10^{17}$ eV is confirmed. After adjustment of parameters and additional exposition at the Yakutsk array there are three events with energy $E > 10^{20}$ eV.
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