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Register a new userThe Cosmic-Ray Energy Spectrum between 2 PeV and 2 EeV Observed with the TALE detector in monocular mode
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We report on a measurement of the cosmic ray energy spectrum by the Telescope Array Low-Energy Extension (TALE) air fluorescence detector. The TALE air fluorescence detector is also sensitive to the Cherenkov light produced by shower particles. Low energy cosmic rays, in the PeV energy range, are detectable by TALE as Cherenkov Events. Using these events, we measure the energy spectrum from a low energy of $sim 2$ PeV to an energy greater than 100 PeV. Above 100 PeV TALE can detect cosmic rays using air fluorescence. This allows for the extension of the measurement to energies greater than a few EeV. In this paper, we will describe the detector, explain the technique, and present results from a measurement of the spectrum using $sim 1000$ hours of observation. The observed spectrum shows a clear steepening near $10^{17.1}$ eV, along with an ankle-like structure at $10^{16.2}$ eV. These features present important constraints on galactic cosmic rays origin and propagation models. The feature at $10^{17.1}$ eV may also mark the end of the galactic cosmic rays flux and the start of the transition to extra-galactic sources.
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We report on a measurement of the cosmic ray composition by the Telescope Array Low-Energy Extension (TALE) air fluorescence detector (FD). By making use of the Cherenkov light signal in addition to air fluorescence light from cosmic ray (CR) induced extensive air showers, the TALE FD can measure the properties of the cosmic rays with energies as low as $sim 2$ PeV and exceeding 1 EeV. In this paper, we present results on the measurement of $X_{rm max}$ distributions of showers observed over this energy range. Data collected over a period of $sim 4$ years was analyzed for this study. The resulting $X_{rm max}$ distributions are compared to the Monte Carlo (MC) simulated data distributions for primary cosmic rays with varying composition and a 4-component fit is performed. The comparison and fit are performed for energy bins, of width 0.1 or 0.2 in $log_{10} (E/{rm eV})$, spanning the full range of the measured energies. We also examine the mean $X_{rm max}$ value as a function of energy for cosmic rays with energies greater than $10^{15.8}$ eV. Below $10^{17.3}$ eV, the slope of the mean $X_{rm max}$ as a function of energy (the elongation rate) for the data is significantly smaller than that of all elements in the models, indicating that the composition is becoming heavier with energy in this energy range. This is consistent with a rigidity-dependent cutoff of events from galactic sources. Finally, an increase in the $X_{rm max}$ elongation rate is observed at energies just above $10^{17}$ eV indicating another change in the cosmic rays composition.
Large High Altitude Air Shower Observatory(LHAASO) is a composite cosmic ray observatory consisting of three detector arrays: kilometer square array (KM2A) which includes the electromagnetic detector array and muon detector array, water Cherenkov detector array (WCDA) and wide field of view Cherenkov telescope array (WFCTA). One of the main scientific objectives of LHAASO is to precisely measure the cosmic rays energy spectrum of individual components from 1014 eV to 1018 eV. The hybrid observation will be employed by LHAASO experiment, in which the lateral and longitudinal distributions of the extensive air shower can be observed simultaneously. Thus many kinds of parameters can be used for primary nuclei identification. In this paper, high purity cosmic ray simulation samples of light nuclei component are obtained through Multi-Variable Analysis. The apertures of 1/4 LHAASO array for pure proton and mixed proton and helium (H&He) samples are 900 m2Sr and 1800 m2Sr respectively. A prospect of proton and H&He spectra from 100 TeV to 4 PeV is discussed.
We present a measurement of the energy spectrum of ultra-high-energy cosmic rays performed by the Telescope Array experiment using monocular observations from its two new FADC-based fluorescence detectors. After a short description of the experiment, we describe the data analysis and event reconstruction procedures. Since the aperture of the experiment must be calculated by Monte Carlo simulation, we describe this calculation and the comparisons of simulated and real data used to verify the validity of the aperture calculation. Finally, we present the energy spectrum calculated from the merged monocular data sets of the two FADC-based detectors, and also the combination of this merged spectrum with an independent, previously published monocular spectrum measurement performed by Telescope Arrays third fluorescence detector (Abu-Zayyad {it et al.}, {Astropart. Phys.} 39 (2012), 109). This combined spectrum corroborates the recently published Telescope Array surface detector spectrum (Abu-Zayyad {it et al.}, {Astrophys. Journ.} 768 (2013), L1) with independent systematic uncertainties.
The SPHERE-2 balloon-borne detector designed for extensive air shower (EAS) observations using EAS optical Vavilov-Cherenkov radiation (``Cherenkov light), reflected from the snow-covered surface of Lake Baikal is described. We briefly discuss the concept behind the reflected Cherenkov light method, characterize the conditions at the experimental site and overview the construction of the tethered balloon used to lift the SPHERE-2 telescope above the surface. This paper is mainly dedicated to a detailed technical description of the detector, including its optical system, sensitive elements, electronics, and data acquisition system (DAQ). The results of some laboratory and field tests of the optical system are presented.
The Telescope Array (TA) collaboration has measured the energy spectrum of ultra-high energy cosmic rays with primary energies above 1.6 x 10^(18) eV. This measurement is based upon four years of observation by the surface detector component of TA. The spectrum shows a dip at an energy of 4.6 x 10^(18) eV and a steepening at 5.4 x 10^(19) eV which is consistent with the expectation from the GZK cutoff. We present the results of a technique, new to the analysis of ultra-high energy cosmic ray surface detector data, that involves generating a complete simulation of ultra-high energy cosmic rays striking the TA surface detector. The procedure starts with shower simulations using the CORSIKA Monte Carlo program where we have solved the problems caused by use of the thinning approximation. This simulation method allows us to make an accurate calculation of the acceptance of the detector for the energies concerned.
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