A composition dependent energy scale and the determination of the cosmic ray primary mass in the ankle region

At present there are still several open questions about the origin of the ultra high energy cosmic rays. However, great progress in this area has been made in recent years due to the data collected by the present generation of ground based detectors like the Pierre Auger Observatory and Telescope Array. In particular, it is believed that the study of the composition of the cosmic rays as a function of energy can play a fundamental role for the understanding of the origin of the cosmic rays.The observatories belonging to this generation are composed of arrays of surface detectors and fluorescence telescopes. The duty cycle of the fluorescence telescopes is ∼10% in contrast with the ∼100% of the surface detectors. Therefore, the energy calibration of the events observed by the surface detectors is performed by using a calibration curve obtained from a set of high quality events observed in coincidence by both types of detectors. The advantage of this method is that the reconstructed energy of the events observed by the surface detectors becomes almost independent of simulations of the showers because just a small part of the reconstructed energy (the missing energy), obtained from the fluorescence telescopes, comes from simulations. However, the calibration curve obtained in this way depends on the composition of the cosmic rays, which can introduce biases in composition analyses when parameters with a strong dependence on primary energy are considered. In this work we develop an analytical method to study these effects. We consider AMIGA (Auger Muons and Infill for the Ground Array), the low energy extension of the Pierre Auger Observatory corresponding to the surface detectors, to illustrate the use of the method. In particular, we study the biases introduced by an energy calibration dependent on composition on the determination of the mean value of the number of muons, at a given distance to the showers axis, which is one of the parameters most sensitive to primary mass and has an almost linear dependence with primary energy.     

Cosmic neutrinos from the sources of galactic and extragalactic cosmic rays

Although kilometer-scale neutrino detectors such as IceCube are discovery instruments, their conceptual design is very much anchored to the observational fact that Nature produces protons and photons with energies in excess of 10²⁰ eV and 10¹³ eV, respectively. The puzzle of where and how Nature accelerates the highest energy cosmic particles is unresolved almost a century after their discovery. From energetics considerations we anticipate on the order of 10–100 neutrino events per kilometer squared per year pointing back at the source(s) of both galactic and extragalactic cosmic rays. In this context, we discuss the results of the AMANDA and IceCube neutrino telescopes which will deliver a kilometer-square-year of data over the next 3 years.     

The hybrid energy spectrum of Telescope Array’s Middle Drum Detector and surface array

The Telescope Array experiment studies ultra high energy cosmic rays using a hybrid detector. Fluorescence telescopes measure the longitudinal development of the extensive air shower generated when a primary cosmic ray particle interacts with the atmosphere. Meanwhile, scintillator detectors measure the lateral distribution of secondary shower particles that hit the ground. The Middle Drum (MD) fluorescence telescope station consists of 14 telescopes from the High Resolution Fly’s Eye (HiRes) experiment, providing a direct link back to the HiRes measurements. Using the scintillator detector data in conjunction with the telescope data improves the geometrical reconstruction of the showers significantly, and hence, provides a more accurate reconstruction of the energy of the primary particle. The Middle Drum hybrid spectrum is presented and compared to that measured by the Middle Drum station in monocular mode. Further, the hybrid data establishes a link between the Middle Drum data and the surface array. A comparison between the Middle Drum hybrid energy spectrum and scintillator Surface Detector (SD) spectrum is also shown.     

Evolution of ground-based gamma-ray astronomy from the early days to the Cherenkov Telescope Arrays

Most of what we know of cosmic gamma rays has come from spacecraft, but at energies above tens of GeV it has become possible to make observations with ground-based detectors of enormously greater collecting area. In recent years one such detector type, the cluster of imaging air Cherenkov telescopes, has reached a very productive state, whilst several alternative approaches have been explored, including converted solar power collectors and novel high-altitude particle shower detectors which promised to extend the energy range covered. Key examples of development from 1952 to 2011 are followed, noting the problems and discoveries that stimulated the current work, explaining the logic of the alternative approaches that were taken. The merits of the current major Cherenkov observatories and of other viable detectors are examined and compared, with examples of the astrophysical information they are beginning to provide. The detectors are still evolving, as we still do not understand the processes onto which the gamma rays provide a window. These include the acceleration of Galactic cosmic rays (in particular, the wide-band spectra of radiation from some individual supernova remnants are still hard to interpret), the highly relativistic and variable jets from active galactic nuclei, and aspects of the electrodynamics of pulsars. Larger groups of Cherenkov telescopes still offer the possibility of an increase in power of the technique for resolvable Galactic sources especially.     

Prospects for radio detection of ultra-high energy cosmic rays and neutrinos

The origin and nature of the highest energy cosmic ray events is currently the subject of intense investigation by giant air shower arrays and fluorescent detectors. These particles reach energies well beyond what can be achieved in ground-based particle accelerators and hence they are fundamental probes for particle physics as well as astrophysics. One of the main topics today focuses on the high energy end of the spectrum and the potential for the production of high-energy neutrinos. Above about 10²⁰ eV cosmic rays from extragalactic sources are expected to be severely attenuated by pion photoproduction interactions with photons of the cosmic microwave background. Investigating the shape of the cosmic ray spectrum near this predicted cut-off will be very important. In addition, a significant high-energy neutrino background is naturally expected as part of the pion decay chain which also contains much information.Because of the scarcity of these high-energy particles, larger and larger ground-based detectors have been built. The new generation of digital radio telescopes may play an important role in this, if properly designed. Radio detection of cosmic ray showers has a long history but was abandoned in the 1970s. Recent experimental developments together with sophisticated air shower simulations incorporating radio emission give a clearer understanding of the relationship between the air shower parameters and the radio signal, and have led to resurgence in its use. Observations of air showers by the SKA could, because of its large collecting area, contribute significantly to measuring the cosmic ray spectrum at the highest energies. Because of the large surface area of the moon, and the expected excellent angular resolution of the SKA, using the SKA to detect radio Cherenkov emission from neutrino-induced cascades in lunar regolith will be potentially the most important technique for investigating cosmic ray origin at energies above the photoproduction cut-off.     

The Lateral Trigger Probability function for the Ultra-High Energy Cosmic Ray showers detected by the Pierre Auger Observatory

In this paper we introduce the concept of Lateral Trigger Probability (LTP) function, i.e., the probability for an Extensive Air Shower (EAS) to trigger an individual detector of a ground based array as a function of distance to the shower axis, taking into account energy, mass and direction of the primary cosmic ray. We apply this concept to the surface array of the Pierre Auger Observatory consisting of a 1.5 km spaced grid of about 1600 water Cherenkov stations. Using Monte Carlo simulations of ultra-high energy showers the LTP functions are derived for energies in the range between 10¹⁷ and 10¹⁹ eV and zenith angles up to 65°. A parametrization combining a step function with an exponential is found to reproduce them very well in the considered range of energies and zenith angles. The LTP functions can also be obtained from data using events simultaneously observed by the fluorescence and the surface detector of the Pierre Auger Observatory (hybrid events). We validate the Monte Carlo results showing how LTP functions from data are in good agreement with simulations.     

Capabilities of a giant hybrid air shower detector

Recent reports of superhigh energy cosmic rays beyond the expected spectral cutoff have intensified interest in the unknown origin of the highest energy cosmic rays. There is a need for a much larger data base of more precisely measured air showers. This requires new sensitive detectors of enormous aperture. Combining a ground array of particle counters with an optical detector of atmospheric fluorescence yields a detector of outstanding capability. Such a hybrid detector provides far more accurate measurements of energies, arrival directions, and primary particle atomic masses than can be achieved by either type of detector separately.     

Multi‐Messenger Cosmic Particles

A54 Cosmic Ray Acceleration in Galactic Wind Shocks A71 Detection of Ultra‐High Energy Cosmic Rays and Neutrinos with LOFAR A80 Status of the gravitational‐wave detector GEO600 A87 Recent Results and Future of the MAGIC gamma‐ray telescope A92 Cosmic ray detection with the radio technique A93 Cosmic Ray Physics with IceCube A94 The resonance‐like gamma‐ray absorption processes for use in astrophysics A97 Geometry reconstruction of air shower fluorescence detectors revisited A102 Supermassive Binary Black Holes & Radio Jets A108 Muonic Component of Air Showers Measured by KASCADE‐Grande A110 Towards new frontiers: observation of photons with energies above 10¹⁸ eV A112 The IceCube Neutrino Telescope A114 The ground‐based gamma‐ray observatory CTA A116 IceCube: Recent Results and Prospects A117 Particle Physics with AMANDA and IceCube A118 Altitude dependence of fluorescence light emission by extensive air showers A120 Neutrino‐induced cascades in AMANDA & IceCube A122 Enhancement Telescopes for the Pierre Auger Southern Observatory in Argentina A123 Proton spectra from relativistic shock environments in AGN and GRBs A124 The Baikal Neutrino Telescope – Physics Results A127 Searches for point‐like sources of cosmic neutrinos with IceCube A128 The MAGIC/IceCube Target of Opportunity Programtest run A131 Supernova detection with IceCube: from low to high energy neutrinos A132 Measurement of the UHECR energy spectrum from hybrid data of the Pierre Auger Observatory A133 Extension of IceCube at Lower Energy: the Use of AMANDA as Nested Array and the Future Prospectives A135 Searching for neutrinos with the Pierre Auger Observatory A138 Search for Transient Emission of Neutrinos in IceCube A140 Acoustic Neutrino Detection in Antarctic Ice A159 AMANDA limits on the diffuse muon‐neutrino flux: physics implications A164 Investigation of the Radio Emission of Cosmic Ray Air Showers with LOPES A168 The Northern Site of the Pierre Auger Observatory A170 Shower reconstruction and size spectra with KASCADE‐Grande data A171 Neutrinos from Gamma Ray Bursts: predictions and limits from AMANDA‐II data A172 Simulation study of shower profiles from ultra‐high energy cosmic rays A174 Upper limit to the photon fraction in cosmic rays above 10¹⁹ eV from the Pierre Auger Observatory A176 Astrophysics at MeV energies A180 Study of the Cosmic Ray Composition above 0.4 EeV using the Longitudinal Profiles of Showers observed at the Pierre Auger Observatory A185 Backgrounds for UHE horizontal neutrino showers A186 The Front‐End Cards of the Pierre Auger Surface Detectors: Test Results and Performance in the Field A187 Monte Carlo Studies for MAGIC‐II A194 Measuring the proton‐air cross section from logitudinal air shower profiles A195 The UHECR energy spectrummeasured at the Pierre Auger Observatory A203 Highlights of Observations of Galactic Sources with the MAGIC telescope A207 Adesign study for a 12.5 m ∅︁ Imaging Air Cherenkov Telescope for ground‐based γ ‐ray astronomy A210 The Future of Long‐Wavelengths Radio‐Astronomy in Germany: LOFAR and GLOW A211 Online Monitoring of the Pierre Auger Observatory A216 OPTIMA‐Burst – Catching GRB Afterglows (and other Transients) with High Time Resolution A227 JEM‐EUSO mission A232 Rapid Variations in AGN: Clues on Particle Accelerators A235 Systematic search forVHEgamma‐ray emission from X‐ray bright high‐frequency peaked BL Lac objects A237 Prospects for GeV Astronomy in the Era of GLAST A241 Improvements of the energy reconstruction for the MAGIC telescope by means of analysis and Monte Carlo techniques A265 Discovery of VHE γ ‐rays from BL Lacertae with the MAGIC telescope A266 Results of two observation cycles of LS I+61°303 with the MAGIC telescope A267 Wide Range Multifrequency Observations of Northern TeV Blazars A269 Diffusive and convective cosmic ray transport in elliptical galaxies     

Performance of the Tibet hybrid experiment (YAC-II + Tibet-III + MD) to measure the energy spectra of the light primary cosmic rays at energies 50–10,000 TeV

A new hybrid detector system has been constructed by the Tibet ASγ collaboration at Tibet, China, since 2014 to measure the chemical composition of cosmic rays around the knee in the wide energy range. They consist of an air-shower-core detector-grid (YAC-II) to detect high energy electromagnetic component, the Tibet air-shower array (Tibet-III) and a large underground water-Cherenkov muon-detector array (MD). We have carried out a detailed air-shower Monte Carlo (MC) simulation to study the performance of the hybrid detectors by using CORSIKA (version 6.204), which includes QGSJET01c and SIBYLL2.1 hadronic interaction models. Assumed primary cosmic ray models are based on helium poor, helium rich and Gaisser’s fit compositions around the knee. All detector responses are calculated using Geant4 (version 9.5) according to the real detector configurations and the MC events are reconstructed by the same procedure as the experimental data analysis. The energy determination is made by lateral density fitting (LDF) method using modified NKG function and the separation of the light components (proton, helium) is made by means of the artificial neural network (ANN) method and the random forest (RF) method. The systematic errors of the spectra of proton and helium caused by each steps of the analysis procedure are investigated including the dependence of the MC data on the hadronic interaction models and the primary composition models, and the algorithms for the primary mass identification. The systematic errors of the flux to be obtained by the new experiment are summarized as less than 30% in total. Our results show that the new hybrid experiment is powerful enough to study the chemical composition of the cosmic rays, in particular, to obtain the light-component spectra of the primary cosmic rays in 50–10,000 TeV energy range overlapping to the direct observation data at low energy side and ground-based indirect observations at high energy side. It is possible in this energy range to find the break points of the power indices of proton and helium (the knee of individual component spectrum) which are basically important parameter for the study of the cosmic-ray origin.     

Simulated performance of dedicated Ge-strip Compton telescopes as γ-lens focal plane instrumentation

With focusing of gamma rays in the nuclear-line energy regime starting to establish itself as a feasible and very promising approach for high-sensitivity γ-ray (line) studies of individual sources, optimizing the focal plane instrumentation for γ-ray lens telescopes is a prime concern. Germanium detectors offer the best energy resolution available at ∼2 keV FWHM at 1 MeV and thus constitute the detector of choice for a spectroscopy mission in the MeV energy range. Using a Compton detector focal plane has three advantages over monolithic detectors: additional knowledge about (Compton) events enhances background rejection capabilities, the inherently finely pixellated detector naturally allows the selection of events according to the focal spot size and position, and Compton detectors are inherently sensitive to γ-ray polarization. We use the extensive simulation and analysis package assembled for the ACT vision mission study to explore achievable sensitivities for different Ge Compton focal plane configurations as a first step towards determining an optimum configuration.CBW thanks the Townes Fellowship at UCB and NASA Grant NNG05WC28G for Support.     

Search of ultra high energy cosmic rays’ sources. FRI-radiogalaxy Centaurus A

The propagation of ultra high energy cosmic rays in Galactic and extragalactic magnetic fields is investigated in the present paper. The motion of charged particles of different energies and chemical composition is simulated using different Galactic magnetic field models. Positions for the real sources of events registered at the Auger observatory are calculated taking into account the influence of both Galactic and extragalactic turbulent fields. The possibility of their correlation with the Centaurus A radio galaxy is analyzed.     

Production of neutrons, neutrinos and gamma-rays by a very fast pulsar in the Galactic Centre region

We consider the possibility that the excess of cosmic rays near ∼10¹⁸ eV, reported by the AGASA and SUGAR groups from the direction of the Galactic Centre, is caused by a young, very fast pulsar in the high-density medium. The pulsar accelerates iron nuclei to energies ∼10²⁰ eV, as postulated by the Galactic models for the origin of the highest-energy cosmic rays. The iron nuclei, about 1 yr after pulsar formation, leave the supernova envelope without energy losses and diffuse through the dense central region of the Galaxy. Some of them collide with the background matter creating neutrons (from disintegration of Fe), neutrinos and gamma-rays (in inelastic collisions). We suggest that neutrons produced at a specific time after the pulsar formation are responsible for the observed excess of cosmic rays at ∼10¹⁸ eV. From normalization of the calculated neutron flux to the one observed in the cosmic ray excess, we predict the neutrino and gamma-ray fluxes. It has been found that the 1 km² neutrino detector of the IceCube type should detect from a few up to several events per year from the Galactic Centre, depending on the parameters of the considered model. Moreover, future systems of Cherenkov telescopes (CANGAROO III, HESS, VERITAS) should be able to observe  1–10 TeV  gamma-rays from the Galactic Centre if the pulsar was created inside a huge molecular cloud about  3–10×10³ yr  ago.     

Pionic photons and neutrinos from cosmic ray accelerators

Identifying the accelerators that produce the Galactic and extragalactic cosmic rays has been a priority mission of several generations of high energy gamma ray and neutrino telescopes; success has been elusive so far. Detecting the gamma-ray and neutrino fluxes associated with cosmic rays reaches a new watershed with the completion of IceCube, the first neutrino detector with sensitivity to the anticipated fluxes, and the construction of CTA, a ground-based gamma ray detector that will map and study candidate sources with unprecedented precision. In this paper, we revisit the prospects for revealing the sources of the cosmic rays by a multiwavelength approach; after reviewing the methods, we discuss supernova remnants, gamma ray bursts, active galaxies and GZK neutrinos in some detail.     

Study of dispersion of mass distribution of ultra-high energy cosmic rays using a surface array of muon and electromagnetic detectors

We consider a hypothetical observatory of ultra-high energy cosmic rays consisting of two surface detector arrays that measure independently electromagnetic and muon signals induced by air showers. Using the constant intensity cut method, sets of events ordered according to each of both signal sizes are compared giving the number of matched events. Based on its dependence on the zenith angle, a parameter sensitive to the dispersion of the distribution of the logarithmic mass of cosmic rays is introduced. The results obtained using two post-LHC models of hadronic interactions are very similar and indicate a weak dependence on details of these interactions.     

Instruments of RT-2 experiment onboard CORONAS-PHOTON and their test and evaluation IV: background simulations using GEANT-4 toolkit

Hard X-ray detectors in space are prone to background signals due to the ubiquitous cosmic rays and cosmic diffuse background radiation that continuously bombards the satellites which carry the detectors. In general, the background intensity depends on the space environment as well as the material surrounding the detectors. Understanding the behavior of the background noise in the detector is very important to extract the precise source information from the detector data. In this paper, we carry out Monte Carlo simulations using the GEANT-4 toolkit to estimate the prompt background noise measured with the detectors of the RT-2 Experiment onboard the CORONAS-PHOTON satellite.     

Cosmic ray acceleration in hypernova remnants expanding in wind bubbles of Wolf-Rayet progenitor stars

The determination of the origin of cosmic rays with observed energies in excess of 10¹⁷ eV that exceed the expected energies of cosmic rays accelerated by supernova remnants in the galaxy is a pressing problem in modern astrophysics. Hypernova remnants are one of the possible galactic sources of cosmic rays with energies of up to 10¹⁹ eV. Hypernovae constitute a class of extremely powerful supernova explosions, whose supposed progenitors are massive Wolf-Rayet stars. We analyze the special aspects of acceleration of cosmic rays in hypernova remnants that expand in wind bubbles of Wolf-Rayet progenitor stars. We show that these cosmic rays may attain maximum energies of 10¹⁸ eV even with a relatively conservative choice of acceleration parameters and account for tens of percent of the total cosmic ray flux observed in the vicinity of the earth in the energy range of 10¹⁶–10¹⁸ eV if the galactic hypernova explosion rate in the modern epoch reaches ? _S ～ 10^?4 year^?1.     

Methods for point source analysis in high energy neutrino telescopes

Neutrino telescopes are moving steadily toward the goal of detecting astrophysical neutrinos from the most powerful galactic and extragalactic sources. Here we describe analysis methods to search for high energy point-like neutrino sources using detectors deep in the ice or sea. We simulate an ideal cubic kilometer detector based on real world performance of existing detectors such as AMANDA, IceCube, and ANTARES. An unbinned likelihood ratio method is applied, making use of the point spread function and energy distribution of simulated neutrino signal events to separate them from the background of atmospheric neutrinos produced by cosmic ray showers. The unbinned point source analyses are shown to perform better than binned searches and, depending on the source spectral index, the use of energy information is shown to improve discovery potential by almost a factor of two.     

Galactic PeV neutrinos

The IceCube experiment has detected two neutrinos with energies between 1 and 10 PeV. They might have originated from Galactic or extragalactic sources of cosmic rays. In the present work we consider hadronic interactions of the diffuse very high energy cosmic rays with the interstellar matter within our Galaxy to explain the PeV neutrino events detected in IceCube. We also expect PeV gamma ray events along with the PeV neutrino events if the observed PeV neutrinos were produced within our Galaxy in hadronic interactions. PeV gamma rays are unlikely to reach us from sources outside our Galaxy due to pair production with cosmic background radiation fields. We suggest that in future with simultaneous detections of PeV gamma rays and neutrinos it would be possible to distinguish between Galactic and extragalactic origins of very high energy neutrinos.     

Gamma rays from cosmic radioactivities

Abstract— Gamma rays from radioactive byproducts of cosmic nucleosynthesis are direct messengers from nuclear processes taking place in various cosmic sites, and can be measured with telescopes operated in space. Due to low detector sensitivity, up until now, only a handful of sources have been detected in that electromagnetic window. Cobalt lines from SN1987A and ⁴⁴Ti lines from the Cassiopeia A (Cas A) supernova remnant offer unique constraints on the properties of the innermost regions of core collapse supernovae. Diffuse gamma‐ray lines from the decay of radioactive ²⁶Al and the annihilation of positrons are bright enough for mapping the Milky Way in the MeV regime, and are both measured by recent spaceborne spectrometers with unprecedented precision. This constrains the sources of Al production and the state of interstellar gas in the vicinity of these sites: the total mass of ²⁶Al produced by stellar sources throughout the Galaxy is estimated to be ～3 M_⊙ per Myr, and the interstellar medium near those sources appears to be characterized by velocities of ～100 km s^?1. Positron annihilation must occur in a modestly ionized, warm phase of the interstellar medium, but at present the major positron production site(s) remain unknown. The spatial distribution of the annihilation gamma‐ray emission constrains positron production sites and positron propagation in the Galaxy. ⁶⁰Fe radioactivity has been clearly detected recently; the flux ratio relative to ²⁶Al of about 15% is on the lower side of predictions from massive star and supernova nucleosynthesis models. Those views at nuclear and astrophysical processes in and around cosmic sources by space‐based gamma‐ray telescopes offer invaluable information on cosmic nucleosynthesis.     

Cosmogenic activation in germanium and copper for rare event searches

Experiments looking for rare events like the direct detection of dark matter particles or the nuclear Double Beta Decay are operated in deep underground locations, to suppress or very effectively reduce the effect of cosmic rays; but cosmogenic activation produced at sea level in detectors and other materials can become a serious hazard for them. Copper and germanium are very frequently used in this kind of experiments requiring an ultra-low radioactive background and therefore have been chosen as activation targets in this work. First, the excitation functions for relevant induced long-lived radioactive isotopes have been estimated; special care has been taken in using those calculations giving the best agreement with measured production cross-sections and in distinguishing production by neutrons or by protons when relevant and possible. Then, the corresponding rates of production of the nuclides in natural and enriched (86% ⁷⁶Ge and 14% ⁷⁴Ge) germanium and copper have been evaluated considering two different cosmic ray spectra. Comparison of the obtained activation yields at surface with all the known previous results (based either on calculations or experiments) has allowed to draw conclusions on the general methodology for evaluating cosmogenic activation.