We have already reported the first result on the all-particle spectrum around the knee region based on data from 2000 November to 2001 October observed by the Tibet-III air-shower array. In this paper, we present an updated result using data set collected in the period from 2000 November through 2004 October in a wide range over 3 decades between $10^{14}$ eV and $10^{17}$ eV, in which the position of the knee is clearly seen at around 4 PeV. The spectral index is -2.68 $\pm$ 0.02(stat.) below 1PeV, while it is -3.12 $\pm$ 0.01(stat.) above 4 PeV in the case of QGSJET+HD model, and various systematic errors are under study now.
An all-sky survey performed with the Tibet Air Shower Array (Tibet AS) has found a number of potential point sources of TeV gamma rays. If they are steady sources, the implied Tibet AS fluxes should be visible with strong significance to the Whipple 10-m gamma-ray telescope (E > 400 GeV) with only a short (5 hour) exposure. We have observed four candidate directions from the Tibet-II HD dataset for ~5 hours each with the Whipple telescope. In addition, we observed a new candidate direction from the Tibet-III Phase 1 dataset for 7.5 hours. We have found no corresponding excesses at the flux lev…
Several strong TeV gamma-ray flares were detected from Markarian 421 in the years 2000 and 2001 by the Tibet III air shower array at a level of statistical significance of 5.1 sigma. Markarian 421 was unprecedentedly active at X-ray and TeV gamma-ray energies during this period, and a positive correlation was found between the change of the ASM/RXTE X-ray flux and the Tibet TeV gamma-ray flux. When a power-law energy spectrum for gamma-rays from this source is assumed, the spectral index is calculated to be -3.24+-0.69 at the most active phase in 2001. The spectral index observed by the Tibet …
We propose to build a large water-Cherenkov-type muon-detector array (Tibet MD array) around the 37,000 m$^{2}$ Tibet air shower array (Tibet AS array) already constructed at 4,300 m above sea level in Tibet, China. Each muon detector is a waterproof concrete pool, 6 m wide $\times$ 6 m long $\times$ 1.5 m deep in size, equipped with a 20 inch-in-diameter PMT. The Tibet MD array consists of 240 muon detectors set up 2.5 m underground. Its total effective area will be 8,640 m$^{2}$ for muon detection. The Tibet MD array will significantly improve gamma-ray sensitivity of the Tibet AS array in t…
We searched for pulsed gamma-ray emissions from the Crab pulsar using data of the Tibet-III air shower array from November 1999 through November 2005. No evidence for the pulsed emissions was found in our analysis. Upper limits at different energies were calculated for a $3 σ$ confidence level in the energy range of multi-TeV to several hundred TeV.
The Tibet experiment, operating at Yangbajing (4,300 m above sea level), is the lowest energy air shower array and the new high density array constructed in 1996 has sensitivity to $γ$-ray air showers at energies as low as 3 TeV. With this new array, the Crab Nebula was observed in multi-TeV $γ$-rays and a signal was detected at the 5.5 $σ$ level. We also obtained the energy spectrum of $γ$-rays in the energy region above 3 TeV which partially overlaps those observed with imaging atmospheric Cherenkov telescopes. This is the first observation of $γ$-ray signals from point sources with a conven…
Results on steady TeV $γ$-ray point source search using data taken from the Tibet HD (Feb. 1997 -- Sep. 1999) and Tibet III (Nov. 1999 -- Oct. 2001) arrays are presented. From $0^{\circ}$ to $60^{\circ}$ in declination, significant excesses from the well-known steady source Crab Nebula and the high state of the flare type source Markarian 421 are observed. Because the levels of significance from other positions are not sufficiently high, 90% confidence level upper limits on the flux are set assuming different power law spectra. To allow crosschecking, two independently developed analyses are u…
Since 1996, a hybrid experiment consisting of the emulsion chamber and burst detector array and the Tibet-II air-shower array has been operated at Yangbajing (4300 m above sea level, 606 g/cm^2) in Tibet. This experiment can detect air-shower cores, called as burst events, accompanied by air showers in excess of about 100 TeV. We observed about 4300 burst events accompanied by air showers during 690 days of operation and selected 820 proton-induced events with its primary energy above 200 TeV using a neural network method. Using this data set, we obtained the energy spectrum of primary protons…
We report on the solar diurnal variation of the galactic cosmic-ray intensity observed by the Tibet III air shower array during the period from 1999 to 2003. In the higher-energy event samples (12 TeV and 6.2 TeV), the variations are fairly consistent with the Compton-Getting anisotropy due to the terrestrial orbital motion around the sun, while the variation in the lower-energy event sample (4.0 TeV) is inconsistent with this anisotropy. This suggests an additional anisotropy superposed at the multi-TeV energies, e.g. the solar modulation effect. This is the highest-precision measurement of t…
We searched for steady PeV gamma-ray emission from the Monogem ring region with the Tibet air shower array from 1997 February to 2004 October. No evidence for statistically significant gamma-ray signals was found in a region 111$\degr$ $\leq$ R.A. $<$ 114$\degr$, 12$\fdg$5 $\leq$ decl. $<$ 15$\fdg$5 in the Monogem ring where the MAKET-ANI experiment recently claimed a positive detection of PeV high-energy cosmic radiation, although our flux sensitivity is approximately 10 times better than MAKET-ANI's. We set the most stringent integral flux upper limit at a 99% confidence level of 4.0 $\times…
Since 1996, a hybrid experiment consisting of an emulsion chamber and a burst detector array and the Tibet-II air shower array has been operated at Yangbajing (4300 m above sea level) in Tibet. This experiment can detect air-shower cores, called burst events, accompanied by air showers in excess of about 100 TeV. Using the burst event data observed by this experiment, we discuss the primary cosmic ray composition around the knee in comparison with the Monte Carlo simulations. In this paper, we show that all the features of burst events are wholly compatible with the heavy enriched composition …
The flux upper limits of the diffuse gamma rays, from the inner and outer Galactic planes, are revised by factors of 4.0$\sim$3.7 for mode energies 3$\sim$10 TeV, respectively, by using the simulation results of the effective area ratios for gamma-ray induced showers and cosmic-ray induced ones in the Tibet air shower array. In our previous work, (Amenomori et al., ApJ, 580, 887, 2002) the flux upper limits were deduced only from the flux ratio of air showers generated by gamma rays versus cosmic rays. The details of the simulation are given in the paper (Amenomori et al., Advances in Space Re…
In 1997, the BL Lac Object Mrk 501 entered a very active phase and was the brightest source in the sky at TeV energies, showing strong and frequent flaring. Using the data obtained with a high density air shower array that has been operating successfully at Yangbajing in Tibet since 1996, we searched for gamma-ray signals from this source during the period from February through August in 1997. Our observation detected multi-TeV $γ$-ray signals at the 3.7-Sigma level during this period. The most rapid increase of the excess counts was observed between April 7 and June 16 and the statistical sig…
We present the large-scale sidereal anisotropy ofgalactic cosmic-ray intensity in the multi-TeV region observed with the Tibet-IIIair shower array during the period from 1999 through 2003. The sidereal daily variation of cosmic rays observed in this experiment shows an excess of relative intensity around $4\sim7 $ hours local sidereal time, as well as a deficit around 12 hours local sidereal time. While the amplitude of the excess is not significant when averaged over all declinations, the excess in individual declinaton bands becomes larger and clearer as the viewing direction moves toward th…
The Tibet-III air shower array, consisting of 533 scintillation detectors, has been operating successfully at Yangbajing in Tibet, China since 1999. Using the dataset collected by this array from 1999 November through 2005 November, we obtained the energy spectrum of $γ$-rays from the Crab Nebula, expressed by a power law as $(dJ/dE) = (2.09\pm0.32)\times10^{-12} (E/{\rm 3 TeV})^{-2.96\pm0.14} {\rm cm}^{-2} {\rm s}^{-1} {\rm TeV}^{-1}$ in the energy range of 1.7 to 40 TeV. This result is consistent with other independent $γ$-ray observations by imaging air Cherenkov telescopes. In this paper, …
Data from the Tibet-III air shower array (with energies around 3 TeV) and from the Tibet-II array (with energies around 10 TeV) have been searched for diffuse gamma rays from the Galactic plane. These arrays have an angular resolution of about 0.9 degrees. The sky regions searched are the inner Galaxy, 20 degrees <= l <= 55 degrees, and outer Galaxy, 140 degrees <= l <= 225 degrees, and |b| <= 2 degrees or <= 5 degrees. No significant Galactic plane gamma-ray excess was observed. The 99% confidence level upper limits for gamma-ray intensity obtained are (for |b| <= 2 degrees) 1.1 times 10^{-15…
Using the data taken from Tibet II High Density (HD) Array (1997 February-1999 September) and Tibet-III array (1999 November-2005 November), our previous northern sky survey for TeV $γ-$ray point sources has now been updated by a factor of 2.8 improved statistics. From $0.0^{\circ}$ to $60.0^{\circ}$ in declination (Dec) range, no new TeV $γ-$ray point sources with sufficiently high significance were identified while the well-known Crab Nebula and Mrk421 remain to be the brightest TeV $γ-$ray sources within the field of view of the Tibet air shower array. Based on the currently available data …
Recent results of the KASCADE air shower experiment are presented in order to shed some light on the astrophysics of cosmic rays in the region of the knee in the energy spectrum. The results include investigations of high-energy interactions in the atmosphere, the analysis of the arrival directions of cosmic rays, the determination of the mean logarithmic mass, and the unfolding of energy spectra for elemental groups.
We obtained new upper limits on the diffuse gamma rays from the inner Galactic (IG) and outer Galactic (OG) planes in 3.10 TeV region, using the Tibet air shower data and new Monte Carlo simulation results. A difference of the effective area of the air-shower array for observing gamma rays and cosmic rays was carefully taken into account in this analysis, resulting in that the flux upper limits of the diffuse TeV gamma rays were reduced by factors of 4.0.3.7 for 3.10 TeV than those in our previous results (Amenomori, M., Ayabe, S., Cui, S.W., et al. Observation of multi-TeV diffuse gamma rays …
Detailed investigations of extensive air showers have been performed with the data measured by the KASCADE experiment. The results allow to evaluate hadronic interaction models, used in simulations to interpret air shower data. The all-particle spectrum of cosmic rays and their mass composition, as well as individual spectra for groups of elements have been reconstructed. The results suggest, the knee in the all-particle cosmic--ray energy spectrum is caused by a rigidity-dependent cut-off of individual element groups.
We have shown that the Sun's shadow by high energy cosmic rays moves year by year and its behavior is correlated with a time variation of the large-scale structure of the solar and interplanetary magnetic fields. The solar activity was near minimum in the period from 1996 through 1997. Using the data obtained with the Tibet air shower array, we examined the shadowing of cosmic rays by the Sun in this quiet phase of solar cycle, and found that the Sun's shadow was just in the apparent direction of the Sun, though it was observed at the position considerably away from the Sun to the south-west i…
The Tibet air shower array, which has an effective area of 37,000 square meters and is located at 4300 m in altitude, has been observing air showers induced by cosmic rays with energies above a few TeV. We are planning to add a large muon detector array to it for the purpose of increasing its sensitivity to cosmic gamma rays in the 100 TeV (10 - 1000 TeV) energy region by discriminating them from cosmic-ray hadrons. We report on the possibility of detection of gamma rays in the 100 TeV energy region in our field of view, based on the improved sensitivity of our air shower array deduced from th…
Results of experiments investigating air showers in the energy region of the knee are summarized. The all-particle energy spectrum, the mean logarithmic mass, and the average depth of the shower maximum will be discussed. Spectra for groups of elements from air shower data are compared to results from direct measurements.
The small change in the spectral slope of the overall intensity of cosmic rays near 1 PeV may be associated with the endpoint energy of supernova shock acceleration. A crucial test of this connection and other ideas of the origin of the spectral `knee' is the reliable determination of the variation of elemental composition in this region. Recent measurements at the DICE/CASA/MIA air shower installation in Dugway, Utah, USA have provided several independent air shower parameters for each event. The derivation of elemental composition from a combination of Cherenkov size, depth of shower maximum…
The Tibet air shower array, which has an effective area of 37,000 square meters and is located at 4300 m in altitude, has been observing air showers induced by cosmic rays with energies above a few TeV. We have a plan to add a large muon detector array to it for the purpose of increasing its sensitivity to cosmic gamma rays in the 100 TeV energy region by discriminating them from cosmic-ray hadrons. We have deduced the attainable sensitivity of the muon detector array using our Monte Carlo simulation. We report here on the detailed procedure of our Monte Carlo simulation.
The energies of cosmic rays, fully ionized charged nuclei, extend over a wide range up to 10^20 eV. A particularly interesting energy region spans from 10^14 to 10^18 eV, where the all-particle energy spectrum exhibits two interesting structures, the 'knee' and the 'second knee'. An explanation of these features is thought to be an important step in understanding of the origin of the high-energy particles. Recent results of air shower experiments in this region are discussed. Special attention is drawn to explain the principle of air shower measurements - a simple Heitler model of (hadronic) a…
A hybrid experiment consisting of emulsion chambers, burst detectors and the Tibet II air-shower array was carried out at Yangbajing (4,300 m a.s.l., 606 g/cm$^2$) in Tibet to obtain the energy spectra of primary protons and heliums. From three-year operation, these energy spectra are deduced between $10^{15}$ and $10^{16}$ eV by triggering the air showers associated with a high energy core and using a neural network method in the primary mass separation. The proton spectrum can be expressed by a single power-law function with a differential index of $-3.01 \pm 0.11$ and $-3.05 \pm 0.12$ based…
28 size spectra of extensive air showers from 7 different experiments are analysed consistently. They are fitted by adjusting either 4 or 5 parameters: knee position, power law exponents above and below the knee, overall intensity and, in addition, a parameter describing the smoothness of the bend. The residuals are then normalized to the same knee position and averaged. When 5 parameters are employed no systematic deviation from a single smooth knee is apparent at the 1% level up to a factor of 4 above the knee. At larger shower sizes a moderately significant deviation can be seen whose shape…
We present an updated all-particle energy spectrum of primary cosmic rays in a wide range from 10^14 eV to 10^17 eV using 5.5 times 10^7 events collected in the period from 2000 November through 2004 October by the Tibet-III air-shower array located at 4300 m above sea level (atmospheric depth of 606 g/cm^2). The size spectrum exhibits a sharp knee at a corresponding primary energy around 4 PeV. This work uses increased statistics and new simulation calculations for the analysis. We performed extensive Monte Carlo calculations and discuss the model dependences involved in the final result assu…
Recent results of advanced experiments with sophisticated measurements of cosmic rays in the energy range of the so called knee at a few PeV indicate a distinct knee in the energy spectra of light primary cosmic rays and an increasing dominance of heavy ones towards higher energies. This leads to the expectation of knee-like features of the heavy primaries at around 100 PeV. To investigate in detail this energy region several new experiments are or will be devised.
The Karlsruhe multi-detector set-ups KASCADE, KASCADE-Grande, and LOPES aim on measurements of cosmic rays in the energy range of the so called knee between 10^14 eV and 10^18 eV. The multidimensional analysis of the air shower data measured by KASCADE indicates a distinct knee in the energy spectra of light primary cosmic rays and an increasing dominance of heavy ones towards higher energies. This provides, together with the results of large scale anisotropy studies, implications for discriminating astrophysical models of the origin of the knee. To improve the reconstruction quality and stati…
Recent results from the KASCADE extensive air shower experiment are presented. After briefly reviewing the status of the experiment we report on tests of hadronic interaction models and emphasize the progress being made in understanding the properties and origin of the knee at $E_{knee} ~ 4.10^{15} eV. Analysing the muon- and hadron trigger rates in the KASCADE calorimeter as well as the global properties of high energy hadrons in the shower core leads us to conclude that QGSJET still provides the best overall description of EAS data, being superior to DPMJET II-5 and neXus 2, for example. Per…
A brief motivation for studying cosmic rays at energies 10^14 < E < 10^17 eV is given. Besides astrophysical interests in identifying and understanding their sources, there are also particle physics aspects related to their transport properties in the galaxy or to their detection via extensive air showers. The KASCADE air shower experiment taking data at Forschungszentrum Karlsruhe (Germany) provides important information to both of these topics of particle-astrophysics research. A target of particular interest is the so-called 'knee' in the cosmic ray energy spectrum at E_k = 4 x 10^15 eV. Re…
The extensive air shower (EAS) experiment KASCADE has started data taking at the laboratory site of the Forschungszentrum Karlsruhe. The major goal is to determine the elemental composition of the primary cosmic ray particles in the energy range around and above the knee at $E_{\rm k} \approx 5 \cdot 10^{15}$ eV. Here, we shall discuss some results on tests of hadronic interaction models required for air shower simulations, present the `knee' in particle size distributions of electrons, muons, and hadrons, and finally discuss preliminary results on the elemental composition which are based on …
We have observed the shadowing of galactic cosmic ray flux in the direction of the moon, the so-called moon shadow, using the Tibet-III air shower array operating at Yangbajing (4300 m a.s.l.) in Tibet since 1999. Almost all cosmic rays are positively charged; for that reason, they are bent by the geomagnetic field, thereby shifting the moon shadow westward. The cosmic rays will also produce an additional shadow in the eastward direction of the moon if cosmic rays contain negatively charged particles, such as antiprotons, with some fraction. We selected 1.5 x10^{10} air shower events with ener…
Primary cosmic ray particles above energies of about 100 TeV are investigated by large-area ground based detector installations, observing various components of the development of extensive air-showers (EAS). By such an indirect access to the primary cosmic ray spectrum a steepening of the power-law falls off at around 3-5 PeV, known as the {\em knee} has been identified. Different experimental techniques are used to deduce mass- and energy-sensitive observables of EAS experiments. The experiments involve measurements of secondary particle distributions at various observation levels and of muo…
The energy spectrum and primary composition of cosmic rays with energy between $3\times 10^{14}$ and $3\times10^{16}\unit{eV}$ have been studied using the CASA-BLANCA detector. CASA measured the charged particle distribution of air showers, while BLANCA measured the lateral distribution of Cherenkov light. The data are interpreted using the predictions of the CORSIKA air shower simulation coupled with four different hadronic interaction codes. The differential flux of cosmic rays measured by BLANCA exhibits a knee in the range of 2--3 PeV with a width of approximately 0.5 decades in primary en…
Measurements of the lateral distribution of Cherenkov photons with the wide-angle atmospheric Cherenkov light detector array AIROBICC and of the charged particle lateral distribution with the scintillator matrix of the HEGRA air-shower detector complex in air showers are reported. With the atmospheric shower-front sampling technique these detectors measure the electromagnetic component of an extensive air shower via the lateral density distribution of the shower particles and of the Cherenkov photons. The data are compared with events generated with the CORSIKA program package with the QGSJET …
Results from the KASCADE air shower experiment investigating the origin of cosmic rays in the energy region from 10^13 to 10^17 eV are presented. Attention is drawn on the investigation of interactions in the atmosphere and the energy spectrum and mass composition of cosmic rays.
A sudden steepening of the cosmic-ray energy spectrum (the knee) is observed at an energy of about 3 PeV (1 PeV = 10$^{15}$eV). The recent results on extensive air showers allow us to conclude that: a) the knee has an astrophysical origin; b) the 'sharpness' and the fine structure of the knee rule out 'Galactic Modulation' as the origin of the knee; c) most likely the knee is the result of the explosion of a single, recent, nearby supernova.
A sudden steepening of the cosmic-ray energy spectrum (the knee) is observed at an energy of about 3 PeV (1 PeV = $10^{15}$ eV). The experimental study of the PeV cosmic rays has intensified greatly during the last 3 years. The recent results on extensive air showers allow us to conclude that: a) the knee has an astrophysical origin; b) the `sharpness' and the fine structure of the knee rule out `Galactic Modulation' as the origin of the knee; c) most likely the knee is the result of the explosion of a single, recent, nearby supernova.
The cosmic ray primary composition in the energy range between 10**15 and 10**16 eV, i.e., around the "knee" of the primary spectrum, has been studied through the combined measurements of the EAS-TOP air shower array (2005 m a.s.l., 10**5 m**2 collecting area) and the MACRO underground detector (963 m a.s.l., 3100 m w.e. of minimum rock overburden, 920 m**2 effective area) at the National Gran Sasso Laboratories. The used observables are the air shower size (Ne) measured by EAS-TOP and the muon number (Nmu) recorded by MACRO. The two detectors are separated on average by 1200 m of rock, and lo…
It is shown that Extensive Air Shower (EAS) longitudinal development has a critical point where an equilibrium between the main hadronic component and the secondary electromagnetic one exhibits a brake. This results in a change of slope in quasi-power law function $N_{e}(Eo)$. The latter leads to a knee in the EAS size spectrum at primary energy of about 100 TeV/nucleon. Many ``strange'' experimental results can be successfully explained in the frames of current approach.
The problem of the uniqueness of solutions during the evaluation of primary energy spectra in the knee region using an extensive air shower (EAS) data set and the EAS inverse approach is investigated. It is shown that the unfolding of primary energy spectra in the knee region leads to mutually compensative pseudo solutions. These solutions may be the reason for the observed disagreements in the elementary energy spectra of cosmic rays in the 1-100 PeV energy range obtained from different experiments.
Frequency distributions of local muon densities in high-energy extensive air-showers (EAS) are presented as signature of the primary cosmic ray energy spectrum in the knee region. Together with the gross shower variables like shower core position, angle of incidence, and the shower sizes, the KASCADE experiment is able to measure local muon densities for two different muon energy thresholds. The spectra have been reconstructed for various core distances, as well as for particular subsamples, classified on the basis of the shower size ratio N_mu/N_e. The measured density spectra of the total sa…
The knee in the all-particle energy spectrum is scrutinized with a phenomenological model, named poly-gonato model, linking results from direct and indirect measurements. For this purpose, recent results from direct and indirect measurements of cosmic rays in the energy range from 10 GeV up to 1 EeV are examined. The energy spectra of individual elements, as obtained by direct observations, are extrapolated to high energies using power laws and compared to all-particle spectra from air shower measurements. A cut-off for each element proportional to its charge Z is assumed. The model describes …
New results of an analysis of arrival directions of extensive air showers registered with the EAS--1000 Prototype array from August 1997 till February 1999 are presented. The method of Alexandreas et al., which has been used for analysis of data registered with CYGNUS, Milagrito, HEGRA AIROBICC, KASCADE and a number of other experiments, is employed. The existence of zones of excessive flux of cosmic rays with energies in the region of the knee is confirmed, as well as closeness of the zones to coordinates of possible astrophysical cosmic ray sources.
Influence of shower fluctuations on the shape of lateral distribution of electrons in EAS of fixed size measured by scintillation counters is analyzed in framework of scaling formalism. Correction factors for the mean square radius of electrons are calculated for the experimental conditions of KASCADE array. Possible improvement of the primary mass discrimination by analysis of lateral distribution of EAS electrons is discussed in detail.
An RPC carpet covering about 10^4 m^2 (ARGO-YBJ experiment) will be installed in the YangBaJing Laboratory (Tibet, P.R. China) at an altitude of 4300 m a.s.l. . A test-module of about 50 m^2 has been put in operation in this laboratory and about 10^6 air shower events have been collected. The carpet capability of reconstructing the shower features is presented.
The energy dependence of such characteristics as a ratio of the total number of charged particles to the total flux of EAS Cherenkov radiation, a ratio of E(thr)>=1GeV muon flux density at the distance of 600m from a shower core to charged particle flux density, a ratio of the energy transferred to the electromagnetic component of EAS to the primary particle energy is presented. Their comparison with two-component mass composition of cosmic rays (p-Fe) in the framework of calculations by a QGSJET model is given.
The determination of the primary cosmic ray mass composition from the characteristics of extensive air showers (EAS), obtained at an observation level in the lower half of the atmosphere, is still an open problem. In this work we propose a new method of the Multiparametric Topological Analysis and show its applicability for the determination of the mass composition of the primary cosmic rays at the PeV energy region.
The most recent experimental results on the cosmic ray composition and energy spectrum above 1 TeV are reviewed and discussed. All data agree on the presence of the so-called ``knee'' at an energy E(knee) = 3-4 PeV; the knee is seen in all the components of the Extensive Air Showers. These results support the hypothesis of an astrophysical origin of the knee, while no new features in the hadronic interactions at high energies are envisaged. The cosmic ray composition below and above the knee region is still an open question. According to most experiments, the knee seems to be due to the light …
A new extensive air shower (EAS) experiment has been installed at the laboratory site of the Forschungszentrum Karlsruhe. The major goal of the experiment is to determine the chemical composition in the energy range around and above the knee of the primary cosmic ray spectrum. An important advantage of the installation is the capability to simultaneously measure the electromagnetic, muonic and hadronic components of EAS event-by-event, thereby reducing systematic uncertainties to a large extend. Data taking with a large part of the experiment has started at the end of 1995 with further install…
The main goals of the KASCADE (KArlsruhe Shower Core and Array DEtector) experiment are the determination of the energy spectrum and elemental composition of the charged cosmic rays in the energy range around the knee at ca. 5 PeV. Due to the large number of measured observables per single shower a variety of different approaches are applied to the data, preferably on an event-by-event basis. First results are presented and the influence of the high-energy interaction models underlying the analyses is discussed.
Recent findings indicate that the Monogem Ring supernova remnant and the associated pulsar PSR B0656+14 may be the 'Single Source' responsible for the formation of the sharp knee in the cosmic ray energy spectrum at $\sim$3PeV. We estimate the contribution of the pulsar B0656+14 to the cosmic rays in the PeV region and conclude that the pulsar cannot contribute more than 15% to the cosmic ray intensity at the knee. Therefore it cannot be the dominant source there and an SNR is still needed. We also examine the possibility of the pulsar giving the peak of the extensive air shower intensity obse…
A new Air Shower Observatory has been constructed in Buenos Aires during 1999, and commissioned and set in operation in 2000. The observatory consists of an array of four water Čerenkov detectors, enclosing a geometrical area of $\sim$ 30.000 m$^{2}$, and is optimized for the observation of cosmic rays in the ``knee'' energy region. The array detects $\sim$ 250 to $\sim$ 1500 showers/day, depending on the selected triggering condition. In this paper, the design and construction of the array, and the automatic system for data adquisition, daily calibration, and monitoring, are described. Also, …
The Dual Imaging Cerenkov Experiment (DICE) was designed and operated for making elemental composition measurements of cosmic rays near the knee of the spectrum at several PeV. Here we present the first results using this experiment from the measurement of the average location of the depth of shower maximum, <X_max>, in the atmosphere as a function of particle energy. The value of <X_max> near the instrument threshold of ~0.1 PeV is consistent with expectations from previous direct measurements. At higher energies there is little change in composition up to ~5 PeV. Above this energy <X_max> is…
KASCADE is a multi-detector setup to get redundant information on single air shower basis. The information is used to perform multiparameter analyses to solve the threefold problem of the reconstruction of (i)the unknown primary energy, (ii) the primary mass, and (iii) to quantify the characteristics of the hadronic interactions in the air-shower development. In this talk recent results of the KASCADE data analyses are summarized concerning cosmic ray anisotropy studies, determination of flux spectra for different primary mass groups, and approaches to test hadronic interaction models. Neither…
Recent results from the KASCADE experiment on measurements of cosmic rays in the energy range of the knee are presented. Emphasis is placed on energy spectra of individual mass groups as obtained from an two-dimensional unfolding applied to the reconstructed electron and truncated muon numbers of each individual EAS. The data show a knee-like structure in the energy spectra of light primaries (p, He, C) and an increasing dominance of heavy ones (A > 20) towards higher energies. This basic result is robust against uncertainties of the applied interaction models QGSJET and SIBYLL which are used …
Measuring the angles of muons and electrons in air showers is proposed as a method for studying the primary cosmic-ray mass composition near the knee of the cosmic-ray energy spectrum at a few $10^{15}$ eV. Conventional tracking detectors at existing air shower arrays could serve this purpose, like the CRT detectors at the HEGRA array. When the average radial muon angles are examined as a function of shower core distance, the experimental resolution can be very well calibrated from the tangential angle distribution. The method is particularly promising for measuring changes in the average mass…
On the basis of the extensive air shower (EAS) data obtained by the GAMMA experiment, the energy spectra and elemental composition of the primary cosmic rays are derived in the 1-100 PeV energy range. The reconstruction of the primary energy spectra is carried out using an EAS inverse approach in the framework of the SIBYLL2.1 and QGSJET01 interaction models and the hypothesis of power-law primary energy spectra with rigidity-dependent knees. The energy spectra of primary H, He, O-like and Fe-like nuclei obtained with the SIBYLL interaction model agree with corresponding extrapolations of the …
