Cosmic Ray Shower Development Research Articles

Site analysis in the Argentinean Andean region for the placement of astrophysical observatories and solar photovoltaic power plants. The case of the “Leoncito 2” site

After a detailed search for possible sites where to place astrophysical facilities in Argentinean Andean region, a location labeled as LEO 2 (31°24′22″ S, 69°29′32″ W, 1630 masl) is proposed. It is placed near the largest Astronomical Observatory of Argentina: Complejo AStronómico El LEOncito (CASLEO). Its advantages are: a good altitude to detect the maximum development of cosmic ray showers, high spectral transmittance to UV and visible ranges, very low aerosol content (mean particle concentration measured at ground with an optical particle counter PM2.5 = 1.52 µg m−3 and PM>2.5 = 6.83 µg m−3, mean Aerosol Optical Depth at 550 nm = 0.027 (measured from space using the SeaWiFS instrument on board of the SeaStar NASA satellite). A local meteorological analysis was done, using data measured in situ, which shows a typical desertic site with the following mean annual (std. dev.) values:mean annual temperature 18.93 (7.66) °C, mean annual relative humidity 28.76 (20.55)%, low/ moderate mean annual average wind speed 11.63 (8.78) km/h, low mean water content (0.73 cm) and rather low mean cloud coverage fraction (cloud coverage fraction): 0.29 (0.02) (for the period 2003–2016 from Aqua/NASA satellite MODIS device) and 0.25 (0.01) (for the period 2000–2016, Terra/NASA satellite MODIS device). Concerning the conditions for the placement of photovoltaic solar power plants, some positive aspects that can be remarked are a large rather flat available surface (336 km2) with very good levels of annual mean horizontal solar irradiation: Global (2334 kWh m−2per year), Direct (3127 kWh m−2 per year) and Diffuse (394 kWh m−2 per year). Optimum angle to place solar panels at this site is determined and the global tilted solar irradiation is calculated (2689 kWh m−2 per year). In comparison with an African (Ouarzazate, Morocco) and Asian (Dubai) sites, the analysed site present better annual irradiation levels being the Global horizontal irradiation at the Argentinean site 8.1% and 10.3% higher than those calculated for the African and Asian site respectively. Also, a comparison is made of different solar cells (monocrystalline Si, polycrystalline Si and perovskite), through the calculation of the generated photocurrent (mean produced solar photovoltaic current per unit cell surface), considering the atmospheric and solar radiation parameters found for the studied site. We thus conclude that the proposed site in the Andes range is well suited for the placement of Astrophysical facilities, as well as Photovoltaic solar power plants.

Average shape of longitudinal shower profiles measured at the Pierre Auger Observatory

The average profiles of cosmic ray shower development as a function of atmospheric depth are measured for the first time with the Fluorescence Detectors at the Pierre Auger Observatory. The profile shapes are well reproduced by the Gaisser-Hillas parametrization at the 1% level in a 500 g/cm2 interval around the shower maximum, for cosmic rays with log(E/eV) > 17.8. The results are quantified with two shape parameters, measured as a function of energy. The average profiles carry information on the primary cosmic ray and its high energy hadronic interactions. The shape parameters predicted by the commonly used models are compatible with the measured ones within experimental uncertainties. Those uncertainties are dominated by systematics which, at present, prevent a detailed composition analysis.

VI School on Cosmic Rays and Astrophysics

VI School on Cosmic Rays and Astrophysics 17-25 November 2015, Chiapas, MexicoThe VI School on Cosmic Rays and Astrophysics was held at the MCTP, at the Autonomous University of Chiapas (UNACH), Tuxtla Gutiérrez, Chiapas, Mexico thanks to the Science for Development ICTP-UNACH-UNESCO Regional Seminar, 17-25 November 2015 (http://mctp.mx/e_VI_School_on_Cosmic_Rays_and_Astrophysics.html).The School series started in La Paz, Bolivia in 2004 and it has been, since then, hosted by several Latin American countires: 1.- La Paz, Bolivia (August, 2004), 2.- Puebla, Mexico (September, 2006), 3.- Arequipa, Peru (September, 2008), 4.- Santo André, Brazil (September, 2010), 5.- La Paz, Bolivia (August, 2012). It aims to promote Cosmic Ray (CR) Physics and Astrophysics in the Latin American community and to provide a general overview of theoretical and experimental issues on these topics. It is directed to undergraduates, postgraduates and active researchers in the field. The lectures introduce fundamental Cosmic Ray Physics and Astrophysics with a review of standards of the field. It is expected the school continues happening during the next years following a tradition.In this edition, the list of seminars included topics such as experimental techniques of CR detection, development of CR showers and hadronic interactions, composition and energy spectrum of primary CR, Gamma-Ray Bursts (GRBs), neutrino Astrophysics, spacecraft detectors, simulations, solar modulation, and the current state of development and results of several astroparticle physics experiments such as The Pierre Auger Observatory in Argentina, HAWC in Mexico, KASCADE and KASCADE Grande, HESS, IceCube, JEM-EUSO, Fermi-LAT, and others.This time the school has been complemented with the ICTP-UNACH-UNESCO Seminar of theory on Particle and Astroparticle Physics. The organization was done by MCTP, the Mesoamerican Centre for Theoretical Physics.The school had 46 participants, 30 students from Honduras, Brazil, Guatemala, Panama, Colombia, Ecuador and Mexico, and 16 lecturers from United States of America, Italy, Japan and Mexico. As a result a total of 17 contributions are included in the present proceedings.Dr. Oscar Saavedra San MartínDr. Karen Salomé Caballero MoraEditors

Universality in the longitudinal development of Cosmic Ray showers

In this work we derive the result that the shape of the longitudinal development of individual very high energy showers, not too far from maximum, has in most cases a simple, smooth shape that resembles a gaussian with a small distortion, so that the post–maximum width of the shower profile is broader than the pre–maximum width. The distortion becomes smaller for larger shower energies. These results are independent from the nature of the primary particle (photon, electron, proton or nucleus) and are related to the fact that the spectra of the particles (e± and γ) that form the dominant component of a shower, have spectra that in good approximation depends only on the shower age. The longitudinal profiles of the showers are therefore reasonably well characterized by only few parameters: the position and size at maximum: tmax and Nmax, the width σ and the asymmetry a. Information about the nature of the primary particles (and the properties of hadronic interactions) can be extracted from statistical studies of the distributions of the shape parameters. Studies of tmax (the position of the shower maximum) are the most sensitive, but also the distributions of the shower width and asymmetry can give valuable information.

Measurement of very forward neutron energy spectra for 7 TeV proton–proton collisions at the Large Hadron Collider

The Large Hadron Collider forward (LHCf) experiment is designed to use the LHC to verify the hadronic-interaction models used in cosmic-ray physics. Forward baryon production is one of the crucial points to understand the development of cosmic-ray showers. We report the neutron-energy spectra for LHC s=7 TeV proton–proton collisions with the pseudo-rapidity η ranging from 8.81 to 8.99, from 8.99 to 9.22, and from 10.76 to infinity. The measured energy spectra obtained from the two independent calorimeters of Arm1 and Arm2 show the same characteristic feature before unfolding the detector responses. We unfolded the measured spectra by using the multidimensional unfolding method based on Bayesian theory, and the unfolded spectra were compared with current hadronic-interaction models. The QGSJET II-03 model predicts a high neutron production rate at the highest pseudo-rapidity range similar to our results, and the DPMJET 3.04 model describes our results well at the lower pseudo-rapidity ranges. However, no model perfectly explains the experimental results over the entire pseudo-rapidity range. The experimental data indicate a more abundant neutron production rate relative to the photon production than any model predictions studied here.

Background radiation measurement with water Cherenkov detectors

Water Cherenkov Detectors have the nice property of being mostly calorimeters for cosmic ray induced electrons and photons, while providing a clear signal for muons. At large energy deposited in the detector, they observe small extended air showers. This makes them interesting detectors to study the background of cosmic ray secondaries. Using low threshold scaler counters, one can follow the flux of cosmic rays on top of the atmosphere, and/or study atmospheric effects on the cosmic ray shower development. In this paper, background data from the Pierre Auger Observatory are presented. These data are searched for short time-scale variation (one second scale, as expected from Gamma Ray Bursts), and larger time-scale variations, showing modulation effects due to Solar activity (Forbush decreases). Rapid changes in the background flux are also observed during the crossing of storms over the 3000 km 2 of the ground array.

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.

Study of the Air Fluorescence by AIRFLY

The fluorescence detection of ultra high energy cosmic rays requires a detailed knowledge of the fluorescence light emission from nitrogen molecules over a wide range of atmospheric parameters, corresponding to altitudes typical for the cosmic ray shower development in the atmosphere. Measurements of the fluorescence yield in atmospheric gases excited by electrons over energies ranging from keV to hundreds of MeV at several accelerators were performed. The spectral distribution of the fluorescent light between 280 nm and 429 nm has been determined with high resolution. Pressure, temperature and humidity dependence of the fluorescence light spectrum excited by MeV electrons in air was studied. A new technique for the measurement of the absolute fluorescence yield of the 337 nm line has been introduces with the aim of reducing the systematic error to below 10 %. The results obtained so far are presented.

Temperature and humidity dependence of air fluorescence yield measured by AIRFLY

The fluorescence detection of ultra high energy cosmic rays requires a detailed knowledge of the fluorescence light emission from nitrogen molecules over a wide range of atmospheric parameters, corresponding to altitudes typical of the cosmic ray shower development in the atmosphere. We have studied the temperature and humidity dependence of the fluorescence light spectrum excited by MeV electrons in air. Results for the 313.6, 337.1, 353.7 and 391.4 nm bands are reported in this paper. We found that the temperature and humidity dependence of the quenching process changes the fluorescence yield by a sizeable amount (up to 20% for the temperature dependence in the 391.4 nm band) and its effect must be included for a precise estimation of the energy of ultra high energy cosmic rays.

Comparison of high energy interaction models used for atmospheric shower simulations above 1 TeV

We present here a comparison of interaction models commonly used for simulating cosmic ray shower development in the atmosphere at energies greater than 1 TeV. The implementations of these models in CORSIKA and the FLUKA transport and interaction code are relevant for extensive air shower experiments, neutrino telescopes, and gamma-ray surfacebased detectors. We compare the pion, kaon, charmed meson and baryon energy fractions and the multiplicities at the first interaction stage of monoenergetic protons on nitrogen nuclei in the range 1 TeV-100 PeV. We also show comparisons in terms of Z-moments, a spectrumweighted multiplicity often used in the cosmic ray community. The transverse and longitudinal momentum distributions of the secondary muons produced in proton-nitrogen collisions are also shown.

Measurement of the zenith angle distribution of the cosmic muon flux in Hanoi

The zenith angle distribution of the cosmic muon flux has been measured in Hanoi, where the geomagnetic rigidity cutoff reaches the very high value of 17 GV, using an orientable scintillator telescope. The measurement is of interest for the understanding of the development of cosmic ray showers in the earth atmosphere. The dependence of the cosmic muon flux (integrated over charges and momenta) on zenith angle θ is measured to be of the approximate form ( Φ 0− asin 2 θ)×cos 2 θ with Φ 0=72.0±1.6 m −2 sr −1 s −1 and a=7.8±0.8 m −2 sr −1 s −1 . This result is consistent with an earlier Hanoi measurement and is in excellent agreement with the prediction of a model widely used in the analysis of atmospheric neutrino data.

Measurement of the vertical cosmic muon flux in a region of large rigidity cutoff

The vertical cosmic muon flux has been measured in Hanoi using a segmented scintillator hodoscope. It is the first measurement performed at VATLY, a cosmic ray laboratory recently created in Vietnam and installed in the premises of the Institute for Nuclear Sciences and Techniques. The measurement, performed at sea level in a region where the geomagnetic rigidity cutoff reaches 17 GV, is of interest for the understanding of the development of cosmic ray showers in the earth atmosphere. The result is compared with the prediction of a model widely used in the analysis of atmospheric neutrino data.

Consequences of parton saturation and string percolation on the development of cosmic ray showers.

At high gluon or string densities, gluon saturation or the strong interaction among strings, either forming color ropes or giving rise to string percolation, induces a strong suppression in the particle multiplicities produced at high energy. This suppression implies important modifications on cosmic ray shower development. In particular, it is shown that it affects the depth of maximum, the elongation rate, and the behavior of the number of muons at energies about 10(17)--10(18) eV. The existing cosmic ray data point out in the same direction.

Parton distribution functions and UHE cosmic-ray interactions

Presents some preliminary results on the interpretation of UHE cosmic rays taking into account the new parametrizations of the parton distribution functions. The (D-) parametrization, which is in favourable agreement with HERA data, results in a faster development of cosmic-ray showers in the atmosphere with an asymptotic behaviour of UHE collisions dominated by the higher multiplicity; the consequences of the other parametrizations (D0), (B0) and (B-) do not differ from those obtained with conventional simulations.

Cosmic Ray Anisotropy and the Knee of the Energy Spectrum

The knee of the cosmic:ray energy spectrum occurs at an energy slightly below 101 6 eV. At a similar energy significant changes are found in cosmic ray shower development and anisotropy. It is suggested that these changes can be understood if there is a general proton dominated cosmic ray flux along our spiral arm from outer galactic regions, which is exceeded by an iron dominated flux from the opposite spiral arm direction at energies between ~ 1014 and ~ 101 7 eV.

Comment on the Cosmic Ray Energy Spectrum in the Light of Results from Atmospheric Cerenkov Studies

New information has recently become available on the development of cosmic ray showers in the atmosphere. This information is used to show that the energy spectrum of cosmic rays must exhibit more pronounced structure than previously thought at energies of about 10'6 eV. Possible interpretations of this structure are discussed

The sensitivity of Cerenkov radiation pulses to the longitudinal development of cosmic-ray showers

Monte-Carlo simulation of electron-photon cascades in the atmosphere have been used to calculate fluxes and time distributions of Cerenkov radiation from air showers. Results are presented which allow the longitudinal development of cosmic-ray showers to be mapped from the time structure of Cerenkov pulses (assuming perfect instrumental time resolution) without further recourse to hadron interaction models. Mapping of the development becomes unreliable using pulses observed much within 170-200 m of the axis (depending on zenith angle). The use of angular distributions given in a preceding paper (ibid., vol.8, p.1461, 1982) proved to be a satisfactory substitute for detailed Monte-Carlo cascade simulations for calculating Cerenkov signals. A sharp shoulder is expected to develop in the lateral distribution of the light in small showers; this should be allowed for in analysing observations.

The elongation rate theorem for cosmic-ray showers and its application

The elongation rate theorem has been proposed by Linsley (1977) as a simple and useful representation for the variation of cosmic-ray shower development with primary energy. Comparison is made of the predictions of the theorem with the results of rigorous computer simulations. Fundamental differences are noted and the effects of these on the applicability of the theorem are discussed.

Cosmic-ray shower development from measurements of the lateral distribution of atmospheric Cerenkov light

Published experimental work on the lateral distribution function of atmospheric Cerenkov light from cosmic-ray showers has been used to relate the shape of this function to the distance of shower maximum from the observer. This relationship has then been used with the authors' own experimental data to investigate the relationship between shower size and depth of shower maximum development for showers in the size range approximately 2*105 to 3*106 particles.

The correlation of two atmospheric Cerenkov techniques for studying cosmic-ray shower development

A comparison of the lateral distribution function and the pulse time profile of Cerenkov light from individual cosmic-ray showers shows good correlation between these parameters for showers with sizes around 106 particles at sea level. This is as would be expected if both parameters reflect the pattern of shower development in the atmosphere. The relationship between them is not in good agreement with a theoretical relationship developed for larger showers.