Study Of Cosmic Rays Research Articles

The northern site of the Pierre Auger Observatory

The Pierre Auger Observatory is an international facility dedicated to the full-sky study of the highest-energy cosmic rays. The southern site of the Auger Observatory was completed in June 2008. Data collected since January 2004 have yielded important information on the energy spectrum, the primary particle composition, the fluxes of photons and neutrinos and on the anisotropic distribution of the arrival directions of the most energetic particles. On this basis, the scientific motivation for the northern Auger Observatory site in Colorado, USA, is discussed. The overall layout, the key components and the expected performance of this 20 000 km2 hybrid observatory comprised of an array of 4400 surface detectors and 39 fluorescence telescopes are described.

Cosmic ray studies with the OPERA detector at Gran Sasso

OPERA is a long-baseline neutrino experiment located in the Hall C of the Gran Sasso underground Laboratory at an average depth of 3.8 km w.e., corresponding to average muon energies at surface higher than 1.4 TeV. After a brief description of the main scientific goals of the experiment, we focus on the potentialities of OPERA used as a cosmic ray detector. In particular, we report on the measurement of the atmospheric muon charge ratio Rμ = Nμ+/Nμ− and on the analysis of upgoing muons induced by atmospheric neutrinos.

The LHCf experiment at LHC

High Energy Cosmic Ray experiments are providing useful information to understand high energy phenomena in the Universe. However, the uncertainty caused from the poor knowledge of the interaction between very high energy primary cosmic ray and the Earth’s atmosphere prevents the precise deduction of astrophysical parameters from the observational data. The Large Hadron Collider (LHC) provides the best opportunity for calibrating the hadron interaction models in the most interesting energy range, between 1015 eV and 1017 eV. To constrain the models used in the extensive air shower simulations the measurements of very forward particles are mandatory. Among the LHC experiments, the LHCf experiment has been designed to reach this goal and its capability to measure forward neutral particle produced in p-p interaction will result crucial for a better interpretation of cosmic ray studies. In this paper, the status of the LHCf experiment and preliminary results for 900 GeV data taking are discussed.

Universality of cosmic ray shower development

The concept of “age” as a parameter for the description of the state of development of high energy showers in the atmosphere has been in use in cosmic ray studies for several decades. In this work we briefly discuss how this concept, originally introduced to describe the average behavior of electromagnetic cascades, can be fruitfully applied to describe individual showers generated by primary particles of different nature, including protons, nuclei and neutrinos. Showers with the same age share three different important properties: (i) their electron size has the same fractional rate of change with increasing depth, (ii) the bulk of the electrons and photons in the shower (excluding high energy particles) have energy spectra with shapes and relative normalization uniquely determined by the age parameter, (iii) the electrons and photons in the shower have also the same angular and lateral distributions sufficiently far from the shower axis. In this work we discuss how the properties associated with the shower age can be understood with simple arguments, and how the shapes of the electron and photon spectra and the relative normalization that correspond to a certain age can be calculated analytically.

The brief history of experimental research of cosmic ray variations in Yakutia

Some unknown historical facts of cosmic ray studies in the north-east of the former Soviet Union related to the Yakutsk scientific group are reported for the benefit of the international scientific community. It focuses on the founders of Yu.G. Shafer Institute of Cosmophysical Research and Aeronomy of Siberian Branch of Russian Academy of Sciences. A chronology of measurements of cosmic ray intensity variations since 1949 in Yakutia (Sakha Republic; NE Siberia) is given. In particular, for the first time the data of the first solar cosmic ray event registered at Yakutsk (GLE04), with a small ionization chamber S-2 (volume: 20 L) are presented. Moreover, the data of the large ionization chamber ASK-1 (volume: 950 L) for the 1953–2003 period useful for specialists in the field of cosmic ray variations are also shown.

History of cosmic ray research in Finland

The history of cosmic ray research in Finland can be traced back to the end of 1950s, when first ground-based cosmic ray measurements started in Turku. The first cosmic ray station was founded in Oulu in 1964 performing measurements of cosmic rays by a muon telescope, which was later complemented by a neutron monitor. Since the 1990s, several research centers and universities, such as The Finnish Meteorological Institute, Helsinki University of Technology, University of Oulu, University of Turku and University of Helsinki have been involved in space science projects, such as SOHO, AMS, Cluster, Cassini, BepiColombo, etc. At the same time, ground-based cosmic ray measurements have reached a new level, including a fully automatic on-line database in Oulu and a new muon measuring underground site in Pyhäsalmi. Research groups in Helsinki, Oulu and Turku have also extensive experience in theoretical investigations of different aspects of cosmic ray physics. Cosmic ray research has a 50-year long history in Finland, covering a wide range from basic long-running ground-based observations to high-technology space-borne instrumentation and sophisticated theoretical studies. Several generations of researchers have been involved in the study ensuring transfer of experience and building the recognized Finnish research school of cosmic ray studies.

Cosmic ray measurements in High Tatra mountains: 1957–2007

Lomnický Štít (LS, situated at High Tatra mountain, 2634 m above sea level, in the direction of 49.40°N, 20.22°E; geomagnetic vertical cut-off rigidity for cosmic rays ∼4 GV) is a relevant place for cosmic ray studies. After a brief review of the LS research history we present a selection of the results based on the measurements performed by the neutron monitor located at that site. In particular, the characteristics of quasi-periodicities and the diurnal variability amplitude and phase obtained from those data are discussed.

Cosmic ray studies at Moussala – Past, present and future

We review the main activities carried out at Moussala peak (2925 m above sea level, 42°11′N, 23°35′E) station in Bulgaria, connected with cosmic ray investigations during the last five decades. Several important results obtained at the station are reported. The detector design and corresponding methodological studies of the presently operational devices are shown as well, precisely the Cherenkov light telescope, lead free neutron monitor and muon telescope. The scientific potential of the existing complex is discussed.

The IGY and beyond: A brief history of ground-based cosmic-ray detectors

The state of art of ground-based cosmic-ray research from its discovery to present is reviewed. After discovery of cosmic rays by Hess in 1912, the nature of the primary and secondary radiation was established from recordings by a variety of instruments, sensitive to various components of cosmic rays and operated at different latitudes, longitudes and altitudes, including instruments carried by balloons. The IGY formalized international co-operation and coordinated study of cosmic rays, which is vital for meaningful interpretation of cosmic-ray data. Data collected at different geographic locations require an effective cutoff rigidity as a data ordering parameter. This parameter is obtained from tracing trajectories of primary cosmic rays in the Earth’s magnetic field. After 50 years the world’s neutron monitor network remains still the backbone for studying intensity variations of primary cosmic rays in the rigidity ranges between 1 and 15 GV, associated with transport and with transient events. Also the penetrating muon and neutrino components of secondary cosmic rays have a long history of recording and fundamental problem investigations. Valuable data about composition and spectrum of primary cosmic rays in ever increasing high-energy regions have been obtained during the years of investigations with various configurations and types of extensive air shower detectors. The culture of personal involvement of the physicist in carrying out experiments and data acquisition characterized the continued vitality of cosmic-ray investigations ranging from its atmospheric, geomagnetic and heliospheric transport through to its solar and astrophysical origins.

High energy cosmic rays

I review here some of the physics we are learning and expect to learn in the near future through the observation of cosmic rays. The study of cosmic rays involves a combination of data from accelerators, ground arrays, atmospheric fluorescence detectors and balloon and satellite experiments. I will discuss the data of the Pierre Auger Observatory, PAMELA, ATIC and FST among other experiments.

The AMS-02 experiment on the ISS

The Alpha Magnetic Spectrometer (AMS-02) on the International Space Station (ISS) is a large acceptance magnetic spectrometer aiming for high precision studies of cosmic rays in space. The experiment will address fundamental questions regarding primary antimatter and dark matter contents of the universe. In addition, the precise measurements of cosmic rays in a wide energy range will result in a greatly improved understanding of the cosmic ray propagation in the Galaxy. The detector is now in its final assembly stage at CERN (Geneva) and it will be shipped to KSC (Florida) for integration with the space shuttle Discovery before the end of 2009. The STS-134 mission, currently scheduled for launch in September 2010 will transport the experiment to the ISS where it will operate for a period of 3 to 5 years.

Cosmic Rays: A Review for Astrobiologists

Cosmic rays represent one of the most fascinating research themes in modern astronomy and physics. Significant progress is being made toward an understanding of the astrophysics of the sources of cosmic rays and the physics of interactions in the ultrahigh-energy range. This is possible because several new experiments in these areas have been initiated. Cosmic rays may hold answers to a great number of fundamental questions, but they also shape our natural habitat and influence the radiation environment of our planet Earth. The importance of the study of cosmic rays has been acknowledged in many fields, including space weather science and astrobiology. Here, we concentrate on the astrobiological aspects of cosmic rays with regard to the enormous amount of new data available, some of which may, in fact, improve our knowledge about the radiation of cosmic origin on Earth. We focus on fluxes arriving at Earth and doses received, and will guide the reader through the wealth of scientific literature on cosmic rays. We have prepared a concise and self-contained source of data and recipes useful for performing interdisciplinary research in cosmic rays and their effects on life on Earth.

Concepts of “age” and “universality” in cosmic ray showers

The concept of ``age'' as a parameter for the description of the state of development of high energy showers in the atmosphere has been in use in cosmic ray studies for several decades. In this work we briefly discuss how this concept, originally introduced to describe the average behavior of electromagnetic cascades, can be fruitfully applied to describe individual showers generated by primary particles of different nature, including protons, nuclei and neutrinos. Showers with the same age share three different important properties: (i) their electron size has the same fractional rate of change with increasing depth, (ii) the bulk of the electrons and photons in the shower (excluding high energy particles) have energy spectra with shapes and relative normalization uniquely determined by the age parameter, and (iii) the electrons and photons in the shower have also the same angular and lateral distributions sufficiently far from the shower axis. In this work we discuss how the properties associated with the shower age can be understood with simple arguments, and how the shapes of the electron and photon spectra and the relative normalization that correspond to a certain age can be calculated analytically.

Between astronomy and particle physics: Outreach at the Pierre Auger Observatory

AbstractThe Pierre Auger Observatory, dedicated to the detection and study of Ultra High Energy Cosmic Rays, has as one of it fundamental missions outreach activities. With this in mind, a specially conceived Visitor Center was included in the design of the Pierre Auger campus in the city of Malargüe, Mendoza, Argentina. One of its main objectives is the contact with the community, through educational courses, talks, conferences and workshops for differen t levels. The permanent exchange between the Pierre Auger scientists and teachers, professionals and society, is important to the impact of the Observatory in the vision by the community of science in general, and scientists in particular. Activities in the outreach area during the last 10 years, resulted in changes to the curricula of study in the schools. Important topics are discussed, like astronomy, light pollution control, and modification of the behavior of the local society. In this presentation we will show how an extensive outreach program, organized by scientists in contact with the community and based on (or near) a research center, can be a factor of social transformation.

Cosmic ray studies with the MINOS detectors

The MINOS experiment uses two layered scintillator and steel detectors along with a muon neutrino beam to search for νμ disappearance, and thus neutrino oscillations. The Far Detector (‘FD’) is situated in a former iron mine in the Soudan Underground Mine State Park in Northeastern MN, 700 m (2070 mwe) below the surface. This 5.4 kt steel/scintillator calorimeter measures the neutrino flux after they have traveled the 735 km baseline. It also detects atmospheric neutrinos at a rate of several per week, and is the first magnetized atmospheric neutrino detector, able to discriminate between νμ and νμ on an event-by-event basis. The similar 1 kt Near Detector (‘ND’) is 100 m (220 mwe) underground at Fermilab. This poster discusses the science being done with the high energy cosmic ray muons which penetrate the rock overburden and are seen by the detectors. The typical surface energy of those seen at the FD are ∼1 TeV (coming from ∼8 TeV primary cosmic rays) and ∼110 GeV at the ND (∼900 GeV primaries).

On the origin of ultra high energy cosmic rays: subluminal and superluminal relativistic shocks

Aims. The flux of ultra high energy cosmic rays (UHECRs) at E > 10 18.5 eV is believed to arise in plasma shock environments in extragalactic sources. In this paper, we present a systematic study of cosmic ray (CR) particle acceleration by relativistic shocks, in particular concerning the dependence on bulk Lorentz factor and the angle between the magnetic field and the shock flow. The contribution to the observed diffuse CR spectrum provided by the accelerated particles is discussed. Methods. For the first time, Monte Carlo simulations for super- and subluminal shocks are extended to boost factors up to Γ= 1000 and systematically compared. The source spectra derived are translated into the expected diffuse proton flux from astrophysical sources by folding the spectra with the spatial distribution of active galactic nuclei (AGN) and gamma ray bursts (GRBs). Results of these predictions are compared with UHECR data. Results. While superluminal shocks are shown to be inefficient at providing acceleration to the highest energies (E > 10 18.5 eV), subluminal shocks may provide particles up to 10 21 eV, limited only by the Hillas-criterion. In the subluminal case, we find that mildly-relativistic shocks, thought to occur in jets of AGN (Γ ∼ 10−30), yield energy spectra of dN/dE ∼ E −2 . Highly relativistic shocks expected in GRBs (100 < Γ < 1000), on the other hand, produce spectra as flat as ∼E −1.0 above 10 9.5 GeV. The model results are compared with the measured flux of CRs at the highest energies and it is shown that, while AGN spectra provide an excellent fit, GRB spectra are too flat to explain the observed flux. The first evidence of a correlation between the CR flux above 5.7 × 10 10 GeV and the distribution of AGN provided by Auger are explained by our model. Although GRBs are excluded as the principle origin of UHECRs, neutrino production is expected in these sources either in mildly or highly relativistic shocks. In particular, superluminal shocks in GRBs may be observable via neutrino and photon fluxes, rather than as protons.

Effect of multiple reusing of simulated air showers in detector simulations

The study of high energy cosmic rays requires detailed Monte Carlo simulations of both, extensive air showers and the detectors involved in their detection. In particular, the energy calibration of several experiments is obtained from simulations. Also, in composition studies simulations play a fundamental role because the primary mass is determined by comparing experimental with simulated data. At the highest energies the detailed simulation of air showers is very costly in processing time and disk space due to the large number of secondary particles generated in interactions with the atmosphere. Therefore, in order to increase the statistics, it is quite common to recycle single showers many times to simulate the detector response. As a result, the events of the Monte Carlo samples generated in this way are not fully independent. In this work we study the artificial effects introduced by the multiple use of single air showers for the detector simulations. In particular, we study in detail the effects introduced by the repetitions in the kernel density estimators which are frequently used in composition studies.

The FLASH thick-target experiment

A key assumption in the reconstruction of extensive air showers using the air fluorescence technique is that fluorescence is proportional to energy deposition at all depths in the shower. This ansatz, along with the supposition that particle distribution and energy loss can be well modeled by modern shower simulation software, must be thoroughly verified. We report here the results of the first direct measurement of air fluorescence yield as a function of shower depth, as performed in the thick-target phase of the FLASH (FLuorescence in Air from SHowers) experimental program at the SLAC Final-Focus Test Beam facility. We compare observed fluorescence light yields as a function of shower depth to concurrently measured charged particle yields, to the energy deposition predictions of the EGS and GEANT software packages, and to empirical energy-deposition models. We also examine the extent to which the relative yield versus shower depth is independent of wavelength within the fluorescence spectrum. We find the proportionality hypothesis to be well supported by the data, validating the use of fluorescence profiles in the study of ultra high energy cosmic rays.

EXPLORING THE ULTRA-HIGH ENERGY SKY: STATUS AND FIRST RESULTS OF THE PIERRE AUGER OBSERVATORY

The Pierre Auger Southern Observatory, a hybrid detector for the study of ultra-high energy cosmic rays (UHECRs), is now operating for more than three years and approaching completion. This paper describes the present status and the performance of the Observatory, with an emphasis on the advantages provided by the combined use of two different detection techniques. A panorama of the most recent results related to the spectrum, composition and arrival directions of the UHECR is then presented, along with a brief discussion of their impact on our knowledge of the UHECRs' origin and composition.

An orientable time-of-flight detector for cosmic rays

Cosmic ray studies, in particular UHECR, can be in general supported by a directional, easily deployable, simple and robust detector. The design of this detector is based on the time of flight between two parallel tiles of scintillator, to distinguish particle passing through in opposite directions; by fine time resolution and pretty adjustable acceptance it is possible to select upward(left)/downward(right) cosmic rays. It has been developed for an array of detectors to measure upward τ from Earth-Skimming neutrino events with energy above 108GeV. The properties and performances of the detector are discussed. Test results from a high noise environment are presented.