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1.
The energy spectrum of cosmic rays with primary energies between 1014 eV and 1016 eV has been studied with the CASA-MIA air shower array. The measured differential energy spectrum is a power law (dj/dE ∝ E−y) with spectral indices γ of 2.66±0.02 below approximately 1015 eV and 3.00±0.05 above. A new method is used for measuring primary energy derived from ground-based data in a compositionally insensitive way. In contrast with some previous reports, the “knee” of the energy spectrum does not appear sharp, but rather a smooth transition over energies from 1015 eV to 3.0 × 1015 eV.  相似文献   

2.
Data taken with ten Cosmic Ray Tracking (CRT) detectors and the HEGRA air-shower array on La Palma, Canary Islands, have been analysed to investigate changes of the cosmic ay mass composition at the ‘knee’ of the cosmic-ray flux spectrum near 1015 eV energy. The analysis is based on the angular distributions of particles in air showers. HEGRA data provided the shower size, direction, and core position and CRT data the particle track information. It is shown that the angular distribution of muons in air showers is sensitive to the composition over a wide range of shower sizes and, thus, primary cosmic-ray energies with little systematic uncertainties. Results can be easily expressed in terms of ln A of primary cosmic rays. In the lower part of the energy range covered, we have considerable overlap with direct composition measurements by the JACEE collaboration and find compatible results in the observed rise of ln A. Above about 1015 eV energy we find no or at most a slow further rise of ln A. Simple cosmic-ray composition models are presented which are fully consistent with our results as well as the JACEE flux and composition measurements and the flux measurements of the Tibet ASγ collaboration. Minimal three-parameter composition models defined by the same power-law slope of all elements below the knee and a common change in slope at a fixed rigidity are inconsistent with these data.  相似文献   

3.
The GU miniarray is a ultra high energy cosmic ray (UHECR) detector consisting of eight plastic scintillators of carpet area 2 m2, each viewed by fast PMTs. It is used to detect Giant EAS by the method of time spread measurement of secondary particles produced in the atmosphere. The energies of the air showers have been reestimated using CORSIKA program. As in the original analysis the Cosmic Ray energy was determined via its relation to the ground level parameter Ns, the shower size. This relation was obtained previously through a best fit relation in agreement with QGS model and Yakutsk data. In this work we use CORSIKA code with QGSJET model of high energy hadronic interactions to simulate miniarray data leading to a modified relation between primary energy and shower size. A revised energy spectrum is reported for 1017–1019 eV primary energy.  相似文献   

4.
《Astroparticle Physics》2004,21(6):565-581
The mass composition of high-energy cosmic rays at energies above 1015 eV can provide crucial information for the understanding of their origin. Air showers were measured simultaneously with the SPASE-2 air shower array and the AMANDA-B10 Cherenkov telescope at the South Pole. This combination has the advantage to sample almost all high-energy shower muons and is thus a new approach to the determination of the cosmic ray composition. The change in the cosmic ray mass composition was measured versus existing data from direct measurements at low energies. Our data show an increase of the mean log atomic mass lnA by about 0.8 between 500 TeV and 5 PeV. This trend of an increasing mass through the “knee” region is robust against a variety of systematic effects.  相似文献   

5.
《Astroparticle Physics》2003,19(6):703-714
The attenuation of the electron shower size beyond the shower maximum is studied with the KASCADE extensive air shower (EAS) experiment in the primary energy range of about 1014–1016 eV. Attenuation and absorption lengths are determined by applying different approaches, including the method of constant intensity, the decrease of the flux of EASs with increasing zenith angle, and its variation with ground pressure. We observe a significant dependence of the results on the applied method. The determined values of the attenuation length ranges from 175 to 196 g/cm2 and of the absorption length from 100 to 120 g/cm2. The origin of these differences is discussed emphasizing the influence of intrinsic shower fluctuations.  相似文献   

6.
The arrival directions of cosmic rays with energies above 1019 eV using data from EAS world arrays are considered. The problem of searching for clusters in arrival directions of the extensive air shower arrays at Yakutsk, Haverah Park, Volcano Ranch, Sydney and Akeno are examined. Four cluster directions are identified which are believed to be significant: these clusters do not lie in the direction of the Galactic Plane.  相似文献   

7.
An interpretation of Akeno giant air shower array (AGASA) data by comparing the experimental results with the simulated ones by cosmic ray simulation for KASCADE (CORSIKA) has been made. General features of the electromagnetic component and low energy muons observed by AGASA can be well reproduced by CORSIKA. The form of the lateral distribution of charged particles agrees well with the experimental one between a few hundred metres and 2000 m from the core, irrespective of the hadronic interaction model studied and the primary composition (proton or iron). It does not depend on the primary energy between 1017.5 and 1020 eV as the experiment shows. If we evaluate the particle density measured by scintillators of 5 cm thickness at 600 m from the core S0(600), suffix 0 denotes the vertically incident shower) by taking into account the similar conditions as in the experiment, the conversion relation from S0(600) to the primary energy is expressed as E (eV)=2.15×1017S0(600)1.015 within 10% uncertainty among the models and composition used, which suggests the present AGASA conversion factor is the lower limit. Although the form of the muon lateral distribution fits well to the experiment within 1000 m from the core, the absolute values change with hadronic interaction model and primary composition. The slope of the ρμ(600) (muon density above 1 GeV at 600 m from the core) vs. S0(600) relation in experiment is flatter than that in simulation of any hadronic model and primary composition. As the experimental slope is constant from 1015 to 1019 eV, we need to study this relation in a wide primary energy range to infer the rate of change of chemical composition with energy.  相似文献   

8.
《Astroparticle Physics》2005,22(5-6):339-353
Data taken during 1997 with the AMANDA-B10 detector are searched for a diffuse flux of neutrinos of all flavors with energies above 1016 eV. At these energies the Earth is opaque to neutrinos, and thus neutrino induced events are concentrated at the horizon. The background are large muon bundles from down-going atmospheric air shower events. No excess events above the background expectation are observed and a neutrino flux following E−2, with an equal mix of all flavors, is limited to E2Φ(1015 eV < E < 3 × 1018 eV)  0.99 × 10−6 GeV cm−2 s−1 sr−1 at 90% confidence level. This is the most restrictive experimental bound placed by any neutrino detector at these energies. Bounds to specific extraterrestrial neutrino flux predictions are also presented.  相似文献   

9.
《Astroparticle Physics》2001,14(4):245-260
Measurements of electron, muon and hadron lateral distributions of extensive air showers as recorded in the Karlsruhe shower core and array detector experiment are presented. The data cover the energy range from 5×1014 eV up to almost 1017 eV and extend from the inner core region to distances of 200 m. The electron and muon distributions are corrected for mutual contaminations by taking into account the detector properties in the experiment. All distributions are well described by NKG functions. The scale radii describing the electron and hadron data best are 30 and 10 m, respectively. We discuss the correlation between the scale radii and the ‘age' parameter as well as their dependence on shower size, zenith angle, and particle energy threshold.  相似文献   

10.
The GREX/COVER_PLASTEX experiment has measured the temporal and spatial fine structure of the EAS disc at sea level in a new and original way, using resistive plate counter detectors for direct measurements of the arrival time of each particle crossing the detector. Data were taken at EAS core distances up to 100 m for shower size N > 105 (PeV energy range). Arrival times of shower particles were measured with nanosecond accuracy. More than 450000 air shower events have been included in this analysis.  相似文献   

11.
《Astroparticle Physics》2003,19(6):715-728
The KASCADE experiment measures a high number of EAS observables with a large degree of sampling of the electron–photon, muon, and hadron components. It provides accurate data for an event-by-event analysis of the primary cosmic ray flux in the energy range around the knee. The possibility of selecting samples of enriched proton and iron induced extensive air showers by applying the statistical techniques of multivariate analyses is scrutinized using detailed Monte Carlo simulations of three different primaries. The purity and efficiency of the proton and iron classification probability is investigated. After obtaining enriched samples from the measured data by application of the procedures the reconstructed number of hadrons, hadronic energy and other parameters are investigated in the primary energy range 1015–1016 eV. By comparing these shower parameters for purified proton and iron events, respectively, with simulated distributions an attempt is made to check the validity of strong interaction models at high energies.  相似文献   

12.
Linsley used the Volcano Ranch array to collect data on the lateral distribution of showers produced by cosmic rays at energies above 1017 eV. Very precise measurements of the steepness of the lateral distribution function were made on 366 events. The current availability of sophisticated hadronic interaction models has prompted an interpretation of the measurements. In this analysis we use the Monte Carlo code to generate showers, together with to simulate the detector response to ground particles. The results show that, with the assumption of a bi-modal proton and iron mix, iron is the dominant component of cosmic rays near 1018 eV, assuming that hadronic interactions are well-described by at this energy range. The Volcano Ranch data set, as available to us, does not allow a straightforward assignment of energy for each event. It is thus not possible to give the energy dependence of the mass composition.  相似文献   

13.
A comparative study of simulated air shower longitudinal profiles is presented. An appropriate thinning level for the calculations is first determined empirically. High statistics results are then provided, over a wide energy range (1014.0–1020.5 eV), for proton and iron primaries, using four combinations of the and program frameworks, and the SIBYLL and QGSjet high energy hadronic interaction models. These results are compared to existing experimental data. The way in which the first interaction controls Xmax is investigated, as is the distribution of Xmax.  相似文献   

14.
In recent years the Fly's Eye and Akeno groups have presented analyses of the cosmic ray mass composition at energies above 1017 eV. While the analysis of the Fly's Eye group points to a likely change in mass composition from heavy to light at energies above 1018 eV, the Akeno analysis favours an unchanging composition. However, the two groups base their conclusions on simulations using quite different hadronic models. Here we present a comparison of the experiments using the same hadronic model and find that the agreement between the experiments is much improved. Under this model, both experiments measure a composition rich in iron around 1017 eV which becomes lighter at higher energies. However, the agreement is not complete, which indicates scope for improvement of the interaction model, or perhaps the need for a re-examination of the experimental results.  相似文献   

15.
We show that the Auger Air Shower Array has the potential to detect neutrinos of energies in the 1019 eV range through horizontal air showers. Assuming some simple conservative trigger requirements, we obtain the acceptance for horizontal air showers as induced by high energy neutrinos by two alternative methods and we then give the expected event rates for a variety of neutrino fluxes as predicted in different models which are used for reference.  相似文献   

16.
Anisotropy in the arrival directions of cosmic rays with energies above 1017 eV is studied using data from the Akeno 20 km2 array and the Akeno Giant Air Shower Array (AGASA), using a total of about 114 000 showers observed over 11 years. In the first harmonic analysis, we have found a strong anisotropy of 4% around 1018 eV, corresponding to a chance probability of 0.2% after taking the number of independent trials into account. 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.  相似文献   

17.
The evolution of the cosmic ray primary composition in the energy range 106–107 GeV (i.e. the “knee” region) is studied by means of the e.m. and muon data of the Extensive Air Shower EAS-TOP array (Campo Imperatore, National Gran Sasso Laboratories). The measurement is performed through: (a) the correlated muon number (Nμ) and shower size (Ne) spectra, and (b) the evolution of the average muon numbers and their distributions as a function of the shower size. From analysis (a) the dominance of helium primaries at the knee, and therefore the possibility that the knee itself is due to a break in their energy spectrum (at EkHe=(3.5±0.3)×106 GeV) are deduced. Concerning analysis (b), the measurement accuracies allow the classification in terms of three mass groups: light (p,He), intermediate (CNO), and heavy (Fe). At primary energies E0≈106 GeV the results are consistent with the extrapolations of the data from direct experiments. In the knee region the obtained evolution of the energy spectra leads to: (i) an average steep spectrum of the light mass group (γp,He>3.1), (ii) a spectrum of the intermediate mass group harder than the one of the light component (γCNO2.75, possibly bending at EkCNO≈(6–7)×106 GeV), (iii) a constant slope for the spectrum of the heavy primaries (γFe2.3–2.7) consistent with the direct measurements. In the investigated energy range, the average primary mass increases from lnA=1.6–1.9 at E01.5×106 GeV to lnA=2.8–3.1 at E01.5×107 GeV. The result supports the standard acceleration and propagation models of galactic cosmic rays that predict rigidity dependent cut-offs for the primary spectra of the different nuclei. The uncertainties connected to the hadronic interaction model (QGSJET in CORSIKA) used for the interpretation are discussed.  相似文献   

18.
We discuss the capability of ‘100 GeV’ class imaging atmospheric Cherenkov telescope (IACT) arrays as future powerful instruments of ground-based gamma-ray astronomy. It is assumed that the array is gathered from individually triggered quadrangular 4-IACT ‘cells’ with a linear size of about 100 m. The multi-cell concept allows coverage of large detection areas economically, and at the same time the effective exploitation of the stereoscopic approach of determination of the shower parameters using information obtained by several IACTs simultaneously. Determination of arrival directions of γ-ray primaries on an event-by-event basis with accuracy δθ ≤ 0.1° combined with high suppression efficiency (at both the hardware and software levels) of the background hadronic showers by a factor of ≈ 103, and large, up to 1 km2 collection areas, can provide minimum detectable energy fluxes of ≥ 100 GeV γ-rays from point sources down to 10−13 erg/cm2 s which is about 3 orders of magnitude lower than the current sensitivities achieved by the satellite-borne detectors at MeV and GeV energies. High sensitivities of multi-IACT arrays would partially compensate the limited efficiency of the technique for all-sky surveys, as well as allow study of moderately extended (≤ 1°) γ-ray sources. IACT arrays with minimum detectable fluence of ≥ 100 GeV γ-rays Sγ < 10−8 erg/cm2 are well suited for effective exploration of highly sporadic nonthermal phenomena from different classes of astrophysical objects on time-scales from ≤ 1 s to several minutes.  相似文献   

19.
The chemical composition of primary cosmic rays with energies from 1015 to 1016.5 eV, so called “knee” region, is examined. We have observed the time structures of air Čerenkov light associated with air showers at Mt. Chacaltaya, Bolivia, since 1995. The distribution of a parameter that characterizes the observed time structures is compared with that calculated with a Monte Carlo technique for various chemical compositions. Then the energy dependence of the average logarithmic mass numbers ln A of the primary cosmic rays is determined. The present result at 1015.3 eV is almost consistent with the result of JACEE (A12) and shows gradual increase in ln A as a function of the primary energy (A24 at 1016 eV). Form the comparison of the observational results with several theoretical models, we conclude that the supernova explosion of massive stars is a plausible candidate for the origin of cosmic rays around the “knee” region.  相似文献   

20.
X-ray transition radiation can be used to measure the Lorentz factor of relativistic particles. At energies approaching γ=E/mc2=105, transition radiation detectors can be optimized by using thick (5–10 mil) foils with large (5–10 mm) spacings. This implies X-ray energies 100 keV and the use of scintillators as the X-ray detectors. Compton scattering of the X-rays out of the particle beam then becomes an important effect. We discuss the design of very high energy detectors, the use of metal radiator foils rather than the standard plastic foils, inorganic scintillators for detecting Compton scattered transition radiation, and the application to the ACCESS cosmic ray experiment.  相似文献   

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