Study Of Cosmic Ray Composition Research Articles

Cosmic-ray measurements with an array of Cherenkov telescopes using reconstruction of longitudinal profiles of air showers

We present a method to reconstruct the longitudinal profile of electrons in showers using Cherenkov telescopes. We show how the Cherenkov light collected by an array of telescopes can be transformed into the number of electrons as a function of atmospheric depth. This method is validated using air shower and simplified telescope simulations. The reconstruction of the depth in which the shower has the maximum number of electrons (Xmax) opens the possibility of cosmic ray composition studies with Cherenkov telescopes in the energy range from 10 to 100 TeV.

Radio wavefront of very inclined extensive air-showers: A simulation study for extended and sparse radio arrays

Radio-detection is becoming an established technique for the detection of air showers induced by cosmic particles. This is in particular true at the highest energies, where very large detection areas are required. A proper description of the shape of the radio wavefront emitted by air showers may allow to reconstruct the properties of its parent particle. In this article, we show that for showers with zenith angles larger than 60° – those targeted by giant radio arrays detecting extensive air showers induced by cosmic particles –, a point-source-like description of the radio wavefront allows to constraint the lateral position of the shower axis within a few meters.Following, we show that the reconstructed longitudinal position of this point source is correlated with the nature of the cosmic rays initiating the shower. Further systematic studies are pending to determine the robustness of this parameter and its validity as a proxy for cosmic ray composition studies.

Determination of cosmic-ray primary mass on an event-by-event basis using radio detection

We present a new methodology to discriminate between light and heavy ultra-high energy cosmic-ray primaries on an event-by-event basis using information from the radio detection of extensive air showers at MHz frequencies. Similarly to other methods to determine primary cosmic ray composition, the one presented here is based on comparisons between detected radio signals and Monte Carlo simulations for multiple primary cosmic ray compositions. Unlike other methods that first reconstruct the depth of maximum shower development Xmax to relate it to the nature of the primaries, we instead infer the cosmic-ray composition directly. The method is most effective in the case of inclined showers that arrive at large zenith angles with respect to the vertical to the ground, where methods based on the determination of Xmax lose accuracy. We show that a discrimination efficiency between 65% and 80% can be reached for zenith angles θ ≳ 60∘, even when typical uncertainties in radio detection are taken into account, including shower energy uncertainty. Our methodology could in principle be applied in large and sparse radio arrays, designed with the large radio footprint of inclined showers in mind, to significantly increase the statistics of ultra-high energy cosmic-ray composition studies.

Performance of tracking stations of the underground cosmic-ray detector array EMMA

The new cosmic-ray experiment EMMA operates at the depth of 75 m (50 GeV cutoff energy for vertical muons; 210 m.w.e.) in the Pyhäsalmi mine, Finland. The underground infrastructure consists of a network of eleven stations equipped with multi-layer, position-sensitive detectors. EMMA is designed for cosmic-ray composition studies around the energy range of the knee, i.e., for primary particles with energies between 1 and 10 PeV. In order to yield significant new results EMMA must be able to record data in the full configuration for about three years. The key to the success of the experiment is the performance of its tracking stations. In this paper we describe the layout of EMMA and construction of the two main detector types used for muon tracking: the high-resolution drift chambers and fast scintillation detector arrays. We also show the measured tracking efficiencies, position and angular resolutions, and sensitivity of drift chambers to the air pressure. The measured angular muon distributions are well reproduced by CORSIKA simulations folded with the known density distribution of the overburden. The single muon flux at the depth of 210 m.w.e. is (1.29 ± 0.06) m−2s−1. This value was determined from the reconstructed tracks registered by a six-layer array of position-sensitive drift chambers.

Muon multiplicities measured using an underground cosmic-ray array

EMMA (Experiment with Multi-Muon Array) is an underground detector array designed for cosmic-ray composition studies around the knee energy (or ~ 1 — 10 PeV). It operates at the shallow depth in the Pyhasalmi mine, Finland. The array consists of eleven independent detector stations ~ 15 m2 each. Currently seven stations are connected to the DAQ and the rest will be connected within the next few months. EMMA will determine the multiplicity, the lateral density distribution and the arrival direction of high-energy muons event by event. The preliminary estimates concerning its performance together with an example of measured muon multiplicities are presented.

Event-by-event study of CR composition with the SPHERE experiment using the 2013 data

We present an event-by-event study of cosmic ray (CR) composition with the reflected Cherenkov light method. The fraction of CR light component above 5 PeV was reconstructed using the 2013 run data of the SPHERE experiment which observed optical Vavilov-Cherenkov radiation of extensive air showers, reflected from snow surface of Lake Baikal. Additionally, we discuss a possibility to improve the elemental groups separability by means of multidimensional criteria.

Cosmic ray composition and energy spectrum from 1–30 PeV using the 40-string configuration of IceTop and IceCube

The mass composition of high energy cosmic rays depends on their production, acceleration, and propagation. The study of cosmic ray composition can therefore reveal hints of the origin of these particles. At the South Pole, the IceCube Neutrino Observatory is capable of measuring two components of cosmic ray air showers in coincidence: the electromagnetic component at high altitude (2835m) using the IceTop surface array, and the muonic component above ∼1TeV using the IceCube array. This unique detector arrangement provides an opportunity for precision measurements of the cosmic ray energy spectrum and composition in the region of the knee and beyond. We present the results of a neural network analysis technique to study the cosmic ray composition and the energy spectrum from 1PeV to 30PeV using data recorded using the 40-string/40-station configuration of the IceCube Neutrino Observatory.

Cosmic ray composition studies through the Gerasimova-Zatsepin effects of heavy nuclei at LAAS

Extensive air showers (EASs) originated from pri- mary cosmic ray energies above 10 15 eV have been measured at multiple EAS observatories deployed in Japan since Sept. 1996. The typical EAS array has been located at the rooftop of the buildings in the university campus, and has GPS- disciplined 10 MHz oscillator to provide the UTC time stamp for each EAS event within a few µs accuracies. Searching for simultaneous and parallel EAS events at multiple EAS observatories due to Gerasimova-Zatsepin (GZ) effects have been carried out by comparing EAS arrival time stamps and directions detected by several baseline combinations of EAS arrays. The EAS pairs whose time difference and angular distance were less than 5 ms and less than 15 respectively, were se- lected and their angular distances from the solar direction and the lunar direction were examined. The data were com- pared with numerical GZ probability as a function of arrival directions of cosmic ray nuclei. Consequently, significant excesses of these events in the solar direction as expected in the numerical prediction of GZ effects were not found. We however found that the deficiencies of EAS pairs in the lunar direction, but its deviation is not significant.

The IceCube Neutrino Observatory - Design and Performance

The IceCube neutrino observatory is currently under construction near the geographic South Pole. Upon completion in 2011 it will consist of two complementary parts, an in-ice array with up to 4800 digital optical modules (DOMs) and a surface array with 320 DOMs. Up to 80 strings of the in-ice detector with 60 modules per string will instrument a cubic kilometer of ice between 1450 to 2450 m depth and will enable the detection of high energy neutrinos produced in astrophysical sources or in the atmosphere. Two surface ice tanks will be installed close to the position of each string, both instrumented with two DOMs. These 160 tanks allow for cosmic ray composition studies. In addition, they are used to reject part of the background in the in-ice array and for the calibration of string modules. After describing the detector design, the performance of the currently installed 9 in-ice strings and 32 surface tanks will be discussed.

Monte Carlo simulation of air shower development for the study of cosmic ray composition

We have developed a Monte Carlo program to simulate the extensive air showers (EASs) in short computing time and to study the chemical composition of cosmic rays at the knee region. This code is particularly applied to the C ̌ erenkov experiment that measures the time structure of C ̌ erenkov light from the EAS. There are many EAS programs available for public use. However, they are not adequate for simulating large number of air shower, since they deal with the very complex interaction algorithm and consume a lot of time. Therefore much faster program should be developed adequately for our purpose. In this report, we discuss the interaction model used in our Monte Carlo code and make a comparison with the accelerator data and the widely used Monte Carlo code, CORSIKA. In addition, we propose a parameterization method that describes the fluctuation of air shower development. Using this method, we can calculate air shower development 10 6 times faster than the CORSIKA simulation code.

Diffuse Continuum Gamma Rays from the Galaxy

A new study of the diUuse Galactic c-ray continuum radiation is presented, using a cosmic-ray propa- gation model which includes nucleons, antiprotons, electrons, positrons, and synchrotron radiation. Our treatment of the inverse Compton scattering includes the eUect of anisotropic scattering in the Galactic interstellar radiation —eld (ISRF) and a new evaluation of the ISRF itself. Models based on locally mea- sured electron and nucleon spectra and synchrotron constraints are consistent with c-ray measurements in the 30¨500 MeV range, but outside this range excesses are apparent. A harder nucleon spectrum is considered but —tting to c-rays causes it to violate limits from positrons and antiprotons. A harder inter- stellar electron spectrum allows the c-ray spectrum to be —tted above 1 GeV as well, and this can be further improved when combined with a modi—ed nucleon spectrum which still respects the limits imposed by antiprotons and positrons. A large electron/inverse Compton halo is proposed which repro- duces well the high-latitude variation of c-ray emission; this is taken as support for the halo size for nucleons deduced from studies of cosmic-ray composition. Halo sizes in the range 4¨10 kpc are favored by both analyses. The halo contribution of Galactic emission to the high-latitude c-ray intensity is large, with implications for the study of the diUuse extragalactic component and signatures of dark matter. The constraints provided by the radio synchrotron spectral index do not allow all of the c-ray emission at less than 30 MeV to be explained in terms of a steep electron spectrum unless this takes the form of a sharp upturn below 200 MeV. This leads us to prefer a source population as the origin of the excess low-energy c-rays, which can then be seen as a continuation of the hard X-ray continuum measured by OSSE, Ginga, and RXT E. Subject headings: cosmic raysdiUuse radiationGalaxy: generalgamma rays: observations ¨ gamma rays: theoryISM: general

Underground muon physics with the MACRO experiment

Underground muon events detected by the MACRO experiment at Gran Sasso have been studied for different purposes. The studies include the vertical muon intensity measurement, multiplicity distribution, lateral and angular muon distribution and searches for substructures inside muon bundles. These analyses have contributed to bring new insights in cosmic ray physics, in particular in the framework of primary cosmic ray composition studies. Moreover, this activity allows the testing and tuning of Monte Carlo simulations, in particular for aspects associated with models of hadronic interactions and muon propagation through the rock.

Review of primary cosmic ray composition studies with underground detectors

The most important results on Cosmic Ray Composition obtained by the underground experiments at different depths are reviewed. Both the stand alone mode and the coincidence with extensive air shower (EAS) detectors are discussed.

Study of cosmic ray composition in the knee region using multiple muon events in the Soudan 2 detector

Deep underground muon events recorded by the Soudan 2 detector, located at a depth of 2100 m of water equivalent, have been used to infer the nuclear composition of cosmic rays in the “knee” region of the cosmic ray energy spectrum. The observed muon multiplicity distribution favors a composition model with a substantial proton content in the energy region 8×105–1.3×107 GeV/nucleus.Received 4 December 1996DOI:https://doi.org/10.1103/PhysRevD.55.5282©1997 American Physical Society

Diffuse galactic gamma-ray continuum emission

Some of the most important questions about the diffuse gamma-ray continuum emission from the Galaxy are reviewed, based on Compton Observatory (CGRO) results, especially COMPTEL and EGRET, and also earlier COS-B analyses. The key issues include the role of emission from cosmic-ray interactions with molecular hydrogen and its energy dependence, emissivity gradients and their interpretation, the cosmic-ray electron spectrum and the effect of discrete sources. The relative contribution of the various emission processes at low and high latitudes is estimated and a plausible synthesis of the observed spectrum over 5 decades of energy is presented. In the energy range above 30 MeV, models based either on explicit cosmic-ray gradients or cosmic-ray/gas coupling can give acceptable fits to the data, and a clear distinction has yet to be made. The quality of the EGRET data may make this possible in the future. The value of the CO-to-H2 conversion factor from γ-rays is still uncertain and there is considerable evidence for cloud-to-cloud variations. The existence of a small emissivity gradient is well established, but is difficult to explain in a diffusive cosmic-ray propagation picture with sources distributed like SNR or pulsars unless there is a larger halo than suggested by cosmic-ray composition studies. In the energy range 1–30 MeV covered by COMPTEL the spectrum of the diffuse emission has been measured and is consistent with a combination of bremsstrahlung and inverse-Compton emission; spatial analysis shows strong evidence for a component with a wide latitude extent which is plausibly identified with the inverse-Compton component. The molecular hydrogen appears to be only a weak γ-ray emitter at low energies, which can be interpreted in terms of reduced MeV cosmic-ray electron density in molecular clouds. New data on the hard X-ray diffuse galactic emission is becoming available and indicates the need for a low-energy upturn in the electron spectrum or some other additional component. The contribution of unresolved sources to the ‘diffuse’ emission is unknown but-probably lies in the range 10–20%. At high latitudes the galactic emission is intense enough to significantly complicate the identification of the extragalactic component; in particular the inverse-Compton emission from a halo a few kpc in extent can account for much of the high-latitude galactic emission. The detection of the Large Magellanic Cloud and the non-detection of the Small Magellanic Cloud provide constraints on extragalactic cosmic-rays, and provide an interesting comparison with the properties of the galactic system. On account of the large amount of data from CGRO now available, this is a subject in rapid development, and this paper provides a snapshot of the situation around mid-1995.

Advances in solid state nuclear track detectors

Several types of commercially available phosphate glasses with a wide range of sensitivities have recently been developed. Chief among these is BP-1, which has a high sensitivity and an unprecedented charge resolution. CR- 39 has been found to respond differently at velocities below ∼10−2 c, where nuclear stopping begins to dominate, than at high velocities, where electronic stopping dominates. Atomic force microscopy has been shown to be a powerful new tool for the study of the etching process, using recoil tracks in mica. CR-39 has been used to set limits on cold fusion rates in strong conflict with rates claimed by some electrochemists. CR-39 and BP-1 have been used to study a number of topics in atomic and nuclear physics including charge pickup in relativistic nucleus-nucleus reactions, nuclear and electromagnetic spallation of relativistic heavy nuclei, the determination of electron attachment and stripping cross sections for relativistic heavy nuclei, and cluster radioactivity. CR-39 is being used to search for strangelets in nature and in ultrarelativistic nucleus-nucleus interactions. Several studies of cosmic ray composition, including TREK, ANTIPODE, HIIS, and UHCRE, are obtaining new results using CR-39, polycarbonate, and BP-1 glass. An experiment to search for weakly interacting massive elementary particles called WIMPs will use mica to detect very short tracks of nuclei that recoil when struck elastically by the WIMPs.

New results on the investigation of the variation of nuclear track detector response with temperature

Track response of polymers is now known to depend on the temperature of the detector during passage of the ionising particle (the registration temperature effect). This has serious consequences for cosmic ray composition studies carried out in earth orbit or on high altitude balloons. Further studies are reported for Lexan, plain CR-39 and doped CR-39 exposed to 245 MeV/N Fe ions. It was found that the relative signal strengths continue to increase down to -137°C, the minimum temperature employed in this experiment. The stack temperatures were cycled between 20°C and -137°C but no evidence of a hysteresis effect. was observed.

Design of emulsion chambers for cosmic ray experiments at balloon altitudes

Emulsion chambers are effective detectors for the study of cosmic ray composition and interactions at balloon altitudes. Important design considerations are discussed and examples of actual chambers are described.

The abundance of Zinc in the cosmic radiation

ABSTRACT Lexan polycarbonate track detector arrays flown from Sioux Falls at an atmospheric depth of ≃ 3.8 g/cm 2 and designed originally for ultra heavy cosmic ray composition studies have been analysed in order to determine the Zn/Ni ratio in the cosmic radiation. Fast scanning procedures which were designed to extract the transcobalt nuclei and discriminate against the overwhelming background of iron events yielded approximately 400 nuclei in the region 28 ≤ Z ≤ 36. The Zn/Ni ratio, based on ten Zn nuclei was found to be (2.4 ± 0.8) × 10 −2 .

An improved CR-39 track detector for cosmic ray applications

ABSTRACT Batches of CR-39 polymer have been produced using a temperature-time polymerisation cycle designed to minimise temperature gradients during curing. Track detector evaluation tests of these batches were carried out using Argon and Iron beams at the LBL Bevalac. The results indicate a significant improvement in the uniformity of track response compared with commercially available CR-39 sheet. This improvement is particularly relevant to the use of CR-39 for cosmic ray composition studies.