Shower Direction Research Articles

Muon production heights determined in the KASCADE experiment

Muon production heights in EAS provide a specific tool to investigate the longitudinal development of EAS, since muons are little affected by subsequent interactions in the atmosphere. Multiplicity of muons presents also a unique tool to investigate hadronic interaction models. The capability of the Muon Tracking Detector to measure radial and tangential angles of muon tracks in EAS, in combination with the shower direction determined by the Array of the KASCADE experiment, has been investigated. Due to different characteristics in shower development of light and heavy primary cosmic ray particles the radial angle and therefore the related production height is sensitive to the mass of them. Muon production height (MPH) and muon production depth (MPD) were studied in different bins of the muon shower size for measured data and MC simulations, which have been performed using the Monte Carlo program CORSIKA with the hadronic interaction models QGSJet and neX us. First composition studies on the basis of MPD distributions have been carried out.

The ALTA global positioning satellite based timing system

The Alberta Large-area Time-coincidence Array (ALTA) experiment uses a number of scintillation detector systems to form a sparse very large area cosmic air-shower detection array. An important scientific goal of the ALTA collaboration is to search for coincidences in the ALTA array due to large area cosmic ray phenomena. A local cosmic ray event, determined by a coincidence of the triplet of cosmic ray detectors forming a local detector system, is time stamped with a temporal coordinate obtained from a GPS receiver. The readout of the data, the local coincidence and the GPS time stamp are all performed in the local readout crate. This time stamp, along with the local shower direction is used to search for coincidences within the large area array. Using two GPS receivers and duplicate sets of ALTA electronics the timing resolution of the GPS time difference between sites was estimated to be 16 ns .

Recent results from L3+COSMICS at CERN L3 collaboration

11 × 10 9 cosmic ray muon events above 20 GeV have been collected with the L3+C detector at LEP, CERN, in 1999 and 2000. During the last year the energy, core position and direction of the air showers causing the observed muons could be derived for part of the data. Preliminary results for the vertical muon flux and charge ratio depending on the muon momentum are shown. The influence of the air shower energy on the muon properties is studied. A search for muon rate increase during the solar flare of the 14 th July 2000 is performed. Meteorological effects on cosmic ray intensity measurements are discussed.

Estimates of arrival directions of giant air showers

The arrival directions of giant air showers generated in the atmosphere by the primary cosmic ray particles with energies above ∼5 · 10 19 eV may be connected with possible extragalactic sources, because the Larmor radius of such particles is too large. Besides it was suggested that the primary particles with enormous energies may be neutrons. In this case it is possible to avoid the energy loss in interactions with the microwave background radiation and arrival directions will strongly point to sources. Thus it is of primary importance to decrease possible errors in the estimates of arrival directions of giant air showers. To estimate the arrival direction of a giant air shower one has to have any model of its space–time structure. The simplest model of the shower time front is a model of the flat front when all particles are located in this front plane. It was shown that possible errors in estimates of the zenith and azimuth angles which characterize the arrival directions may be as large as 5 ◦ or even more. The χ 2 method gives very large values of χ 2 . That means that this model is inconsistent with the data. A much more realistic model of a shower time front was suggested by Linsley. Calculations displayed that both the shower disk thickness and the average time delay depend on the energy of the primary particles. So the calculated time front of the shower for both electrons and muons may fit the data and thus provides better accuracy. The standard mathematical procedure to interpret data is the χ 2 method. This method leads to reasonable estimates of the zenith and azimuth angles with uncertainties of 2÷3 ◦ . In some cases the minimax procedure may be utilized to interpret data. It was shown that the possible error in estimates of the zenith and azimuth angles may be decreased up to 0.5 ◦ . At last the fuzzy uncertain variables and the possibility theory are suggested here to be used for interpreting the data. Calculations were carried out in terms of the quark-gluon string model for primary protons and an observation level of 1020 g/cm. The Landau–Pomeranchuk–Migdal effect and interactions of neutral pions with nuclei in the atmosphere at high energies are taken into account. The Monte Carlo method was used for primary protons while cascades from numerous charged pions were considered with the help of cascade equations. Though experimental statistics is very low no evidence is found to prefer any directions. Thus the isotropic distribution of the arrival directions of giant air showers with

Results from the ARGO-YBJ test experiment

A resistive plate counters (RPCs) carpet of ∼50 m 2 has been put in operation in the Yangbajing Laboratory (Tibet, P.R. China) at 4300 m a.s.l., in order to study the RPCs performance at high altitude and the detector capability of imaging the EAS disc. This test has been performed in view of an enlarged use of RPCs for the ARGO-YBJ experiment. This experiment will be devoted to a wide range of fundamental issues in cosmic rays and astroparticle physics, including in particular γ-ray astronomy and γ-ray bursts physics at energies ⩾100 GeV. In this paper we present and discuss the procedures adopted to calibrate the detector and reconstruct the shower direction. Results concerning many shower features as the angular distribution, the density spectrum, the time profile of the shower front, are found well consistent with the expectation.

Identification of sources of ultrahigh energy cosmic rays

The arrival directions of extensive air showers with energies 4×1019 3σ (σ is the parameter of Gaussian distribution). The Seyfert galaxies are characterized by moderate luminosities (L 1014 eV recorded by the Bolivian and Tian Shan arrays. The source identifications suggest that the gamma rays could have been produced in interactions of cosmic rays with the microwave background radiation and subsequent electromagnetic cascades in intergalactic space. We estimate the strength of intergalactic magnetic fields outside galaxy clusters to be B≤8.7×10−10 G.

Are we making progress in finding the sources of the most energetic cosmic rays?

There is progress, in the sense that although the energies assigned to cosmic rays by air shower arrays may need reducing by about 20%, energy measurements are consistent at about this level, and several experiments now accord with a spectrum which astonishingly shows no GZK cut-off near 10 20 eV, greatly limiting the possible source regions. The simplest interpretation is that few cosmic rays above 10 19 eV come from hundreds of Mpc, contrary to expectation on geometrical grounds. Most of the arrival directions of showers above 4 × 10 19 eV show little correlation with the supergalaxy or with matter concentrations within 200 Mpc. The implications of the spectrum and the arrival directions are discussed. The most likely explanations of their unexpected features are either (a) that these cosmic rays come mainly from the decay of cosmological relic particles clustered in a large galactic halo (though not if photons really do form a large part of the decay spectrum), or (b) that local intergalactic magnetic fields are unexpectedly strong, and disguise the position of and enhance one extraordinary source within a few Mpc, or (c) most particles above 10 19 eV are very different from protons after all, and do not have a threshold for serious energy loss as low as 10 20 eV, or (d) that there is a conspiracy of matching fluxes, so that most cosmic rays above 10 19 eV are from widespread extragalactic sources, but a superimposed hard spectrum from decaying halo relic particles neatly reduces the magnitude of the GZK fall-off above 10 20 eV. Several close pairs of arrival directions may yet turn out to be accidental, but if not, explanations (a) and (b) fail. There are several diagnostic tests to be made by the well-placed first (Southern) Auger Project detector and the High-Resolution Fly's Eye detector.

Reconstruction of showers at TeV energy by the CLUE experiment and its application to recent data

The CLUE UV Cerenkov telescope array has started to take data with 8 telescopes in January 1998. The UV Cerenkov images obtained by the CLUE experiment are very different with respect to the visible case, and a new method for reconstructing the shower direction has been worked out. The shower reconstruction is shown and an application to recent data is given.

An improved technique for the determination of shower geometry from single and stereo IACT images

In order to better utilize the information contained in the shower images generated by imaging Cherenkov telescopes (IACTs) equipped with cameras with small pixels, images are fitted to a parametrization of image shapes gained from Monte Carlo simulations, treating the shower direction, impact point, and energy as free parameters. Monte Carlo studies were carried out for stereoscopic shower images obtained with a system of IACTs. An improvement of order 1.5 in the angular resolution and in the determination of the core position is predicted. The fitting technique can also be applied to single-telescope images. Simulations indicate that the shower direction in space can be reconstructed event-by-event with a resolution of 0.16-. Data from Crab observations with a single HEGRA telescope confirm this prediction.

Changes of the cosmic-ray mass composition in the 10 14–10 16 eV energy range

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 r ay mass composition at the ‘knee’ of the cosmic-ray flux spectrum near 10 15 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 10 15 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.

Characteristics of Air Pollution Condition in Dhaka City

This paper attempts to make clear the characteristics of the magnitude and scope of automotive and factory pollutant emissions in Dhaka city-which are creating an environmental problem in the city. About 451 factories in this city discharge and dump hazardous waste with no regard for the resulting surface and ground water or air-pollution. Most of these factories are bereft of adequate emission treatment. In addition, the increasing traffic, inadequate urban transport infrastructure and services, and an aging and obsolete motor vehicle fleet are giving rise to high air pollution levels. About 86% of the total motor vehicles in this city emit black smoke above the International Standard of 65 HSU. Changing meteorological conditions, such as average wind velocities, wind direction and frequency of showers have influenced the pollutant concentration in the city's air. Without effective measures to control pollutant emissions, the city dwellers will be exposed to unhealthy and dangerous levels of air pollution from automobiles and factories.

Construction and test of a fine-grained liquid argon preshower prototype

A separate liquid argon preshower detector consisting of two layers featuring a fine granularity of 2.5 × 10 −3 was studied by the RD3 collaboration. A prototype covering approximately 0.8 in pseudo-rapidity and 9° in azimuth was built and tested at CERN in July 94. CMOS and GaAs VLSI preamplifiers were designed and tested for this occasion. The combined response of this detector and an accordion electromagnetic calorimeter prototype to muons, electrons and photons is presented. For minimum ionizing tracks a signal-to-noise ratio of 4.5 per preshower layer was measured. Above 150 GeV the space resolution for electrons is better than 250 μm in both directions. The precision on the electromagnetic shower direction, determined together with the calorimeter, is better than 4 mrad above 50 GeV. It is concluded that the preshower detector would adequately fulfil its role for future operation at CERN Large Hadron Collider.

An optimized method for the reconstruction of the direction of air showers for scintillator arrays

An optimized method is presented for the reconstruction of air shower directions for scintillator arrays. The method takes into account that both the expectation value and the spread of the measured arrival times not only depend on the distance of a counter from the shower axis, but also on the number of particles registered in that counter. It also takes into account that the distributions of the measured arrival times are not Gaussian. For showers recorded with the HEGRA scintillator array above the threshold energy of E thres = 20 TeV the mean angular resolution obtained with this method is 〈 σ 63% θ 〉 = 1.0°, and above the threshold E thres = 50 TeV it is 〈 σ 63% θ 〉 = 0.6°. Comparing the new procedure with the HEGRA standard procedure the angular resolution has improved on average by a factor of 1.33. The mis-pointing has been determined with an accuracy of 0.15°. The method is developed using experimental data.

Possible sources of ultrahigh-energy cosmic protons

The arrival directions of showers with energies above 3.2·1019 eV, recorded by the Akeno and AGASA detectors, are analyzed. Their distributions over the celestial sphere are compared with the distributions of possible sources of protons of such high energies. An analysis using three standard deviations of uncertainty in the determination of the arrival directions of the showers shows that the sources of the protons initiating the showers are nuclei of active galaxies with red shifts z≤0.0092, i.e. their distance from us does not exceed 40 Mpc, assuming the Hubble constant is H=75 km/s·Mpc.

Search for correlations between the highest energy cosmic ray showers and gamma ray bursts

We examine the correlation between the arrival directions of ultra high energy cosmic ray showers and gamma ray burst locations from the third BATSE catalog. We find no correlation between the two data sets. We also find no correlations between a pre-GRO burst catalog and the Haverah Park Ultra High Energy shower data that cover approximately the same period of time.

Optimization of angular resolution for air Cherenkov detector arrays for observations of cosmic rays

A recently proposed detector for extremely high energy cosmic rays might exploit the unique properties of air Cherenkov light to optically observe cosmic rays during night, twilight, and possibly during the daytime. We present a method that can be used to accurately reconstruct the direction of the primary cosmic ray. An optimization of the detector station design has been performed via Monte Carlo simulation to maximize angular resolution and minimize cost. Results indicate a configuration consisting of five panels yeidls the best response. These panels are oriented with one panel pointing directly at zenith, while the other four panels are tilted at 60° with respect to the zenith and spaced equally in azimuth. Using this panel configuration we find the original primary shower direction can be reconstructed to an accuracy of 0.3–3°, depending upon the zenith angle of the primary cosmic ray, and the ambient sky background noise. This angular reconstruction accuracy is similar to or better than the traditional angular reconstruction provided by examining the arrival times of charged particles in the extensive air showers.

Calibration and performance of the CHORUS calorimeter

A high resolution calorimeter has been built for CHORUS, an experiment which searches for ν μ → ν τ oscillation in the CERN neutrino beam. Aim of the calorimeter is to measure the energy and direction of hadronic showers produced in interactions of the neutrinos in a nuclear emulsion target and to track through-going muons. It is a longitudinally segmented sampling device made of lead and scintillating fibers or strips. This detector has been exposed to beams of pions and electrons of defined momentum for calibration. The method used for energy calibration and results on the calorimeter performance are reported.

Calibration and performance of the CHORUS calorimeter

A high resolution calorimeter has been built for CHORUS, an experiment which searches for ν μ → ν τ oscillation in the CERN neutrino beam. Aim of the calorimeter is to measure the energy and direction of hadronic showers produced in interactions of the neutrinos in a nuclear emulsion target and to track through-going muons. It is a longitudinally segmented sampling device made of lead and scintillating fibers or strips. This detector has been exposed to beams of pions and electrons of defined momentum for calibration. The method used for energy calibration and results on the calorimeter performance are reported.

Correlation between arrival directions of gamma ray bursts and super high energy EAS

The spatial counterpart between the arrival directions of giant Extensive Air Showers (EAS with energy > 1019 eV) and GRBs has been analysed. The two most energetic phenomena arriving from cosmic space to the Earth are giant EAS and GRBs. The isotropic distribution arrival positions on the sky are characteristic for both components. From the energetic point of view the cosmic-ray particle with such great energy can be produced in a GRB source. Conversely, GRBs can be initiated (as some sort of cascade) by the highest-energy cosmic rays in gaseous or photon targets. The time delay between parent and daughter component can be substantial, but here we do not consider this time correlation. The World Data Centre Catalogue C2, contains the following number of showers registered by arrays: 44 - Volcano Ranch, 144 - Haverah Park and 522 - Sydney. Also the GRBs from BATSE 1B and 2B Catalogs have been analysed. The numbers of EAS in GRB error boxes position have been investigated. There are positions on the sky where the number of EAS exceeds the average value expected for isotropic distributions by 3σ and 5σ (standard deviations).

Shashlik calorimeter Beam-test results

Results from an extensive study of nonprojective Shashlik calorimeter prototypes are reported. Nine (47 × 47 mm 2) towers were exposed to a high energy electron beam at CERN SPS and read out by silicon photodiodes followed by low noise preamplifiers. The main results are the measurements of the energy and shower position resolution and the angular resolution of the electron shower direction. The shower direction measurement is encouraging being in agreement at the tower center with a resolution of σ θ (mrad) = 70/√ E (10 mrad for 50 GeV electrons). The uniformity of the calorimeter response is found to be better than ± 1%. The mean light yield measured in Shashlik towers equipped with Kuraray Y7 WLS fibres and aluminized at the front end of the tower is of the order of 13 photons/MeV.