arXiv subjects

A. D. Supanitsky

Publications and source records attributed to A. D. Supanitsky.

44 records · Page 3Linked to original sources

arXiv2009

A new surface parameter for composition studies at high energies

A new family of parameters intended for composition studies is presented. They make exclusive use of surface data combining the information from the total signal at each triggered detector and the array geometry. We perform an analytical study of these composition estimators in order to assess their reliability, stability and possible optimization. The influence of the different slopes of the proton and Iron lateral distribution function on the discrimination power of the estimators is also studied. Additionally, the stability of the parameter in face of a possible underestimation of the size of the muon component by the shower simulation codes, as it is suggested by experimental evidence, is also studied.

astro-ph.HE↗

arXiv2009

On the possibility of primary identification of individual cosmic ray showers

The transition between the Galactic and extragalactic cosmic ray components could take place either in the region of the spectrum known as the second knee or in the ankle. There are several models of the transition but it is not possible to confirm or even rule out any of them from the flux measurement alone. Therefore, the measurement of the composition as a function of primary energy will play a fundamental role for the understanding of this phenomenon. In this work we study the possibility of primary identification in an event by event basis in the ankle region, around $E = 10^{18}$ eV. We consider as case study the enhancements of the Pierre Auger Southern Observatory, which are under construction in Malague, Province of Mendoza, Argentina. We use a non-parametric technique to estimate the density functions, from Monte Carlo data, corresponding to different combination of mass sensitive parameters and type of primaries. These estimates are used to obtain the classification probability of protons and iron nuclei for the different combination of parameters considered. We find that, after considering all relevant fluctuations, the maximum classification probability obtained combining surface and fluorescence detectors parameters is of order of 90%.

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arXiv2009

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.

astro-ph↗

arXiv2009

A New Numerical Technique to Determine Primary Cosmic Ray Composition in the Ankle Region

In this paper we introduce a new multiparametric technique that attempts to tackle simultaneously the problems of composition determination and hadronic interaction uncertainty. Employing simulations of a real world detector under its planned operational conditions, and disregarding systematics, we can asses that the present technique should be able to determine the composition of a binary mixture of p and Fe with a statistical confidence of few percent, in a way that is independent of the assumed hadronic interaction model. Moreover, the combination of real data with the tools developed and presented here should give an indication of the reliability of the various hadronic interaction models in current use in the area. We center our study in the region of the ankle, where composition carries critical astrophysical information, and use two main parameters: the number of muons at 600 m from the shower axis and the depth of the shower maximum obtained from the hybrid operation of the planned muon counters and high elevation fluorescence telescopes of the AMIGA and HEAT Auger enhancements.

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arXiv2008

Underground Muon Counters as a Tool for Composition Analyses

The transition energy from galactic to extragalactic cosmic ray sources is still uncertain, but it should be associated either with the region of the spectrum known as the second knee or with the ankle. The baseline design of the Pierre Auger Observatory was optimized for the highest energies. The surface array is fully efficient above $3 \times 10^{18}$ eV and, even if the hybrid mode can extend this range below $10^{18}$ eV, the second knee and a considerable portion of the wide ankle structure are left outside its operating range. Therefore, in order to encompass these spectral features and gain further insight into the cosmic ray composition variation along the transition region, enhancements to the surface and fluorescence components of the baseline design are being implemented that will lower the full efficiency regime of the Observatory down to $\sim 10^{17}$ eV. The surface enhancements consist of a graded infilled area of standard Auger water Cherenkov detectors deployed in two triangular grids of 433 m and 750 m of spacing. Each surface station inside this area will have an associated muon counter detector. The fluorescence enhancement, on the other hand, consists of three additional fluorescence telescopes with higher elevation angle ($30^\circ-58^\circ$) than the ones in operation at present. The aim of this paper is threefold. We study the effect of the segmentation of the muon counters and find an analytical expression to correct for the under counting due to muon pile-up. We also present a detailed method to reconstruct the muon lateral distribution function for the 750 m spacing array. Finally, we study the mass discrimination potential of a new parameter, the number of muons at 600 m from the shower axis, obtained by fitting the muon data with the above mentioned reconstruction method.

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arXiv2008

Perturbative exponential expansion and matter neutrino oscillations

We derive an analytical description of neutrino oscillations in matter based on the Magnus exponential representation of the time evolution operator. Our approach is valid in a wide range of the neutrino energies and properly accounts for the modifications that the respective probability transitions suffer when neutrinos originated in different sources traverse the Earth. The present approximation considerably improves over other perturbative treatments existing in the current literature. Furthermore, the analytical expressions derived inside the Magnus framework are remarkably simple, which facilitates their practical use. When applied to the calculation of the day-night asymmetry in the solar neutrino flux our result reproduces the numerical calculation with an accuracy better than 1% for the first order approximation. When the approximation is extended to the second order, the accuracy of the method is further improved by almost one order of magnitude, and it is still better than 5% even for neutrino energies as large as 100 MeV. In the GeV regime characteristic of atmospheric and accelerator neutrinos this accuracy is complemented by a good reproduction of the position of the maxima in the flavor transition probabilities.

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arXiv2007

Analytical description of the Day-Night neutrino asymmetry

We present a new treatment of the Earth matter effects on the neutrino oscillations that is valid for an arbitrary density profile. When applied to the the study of the day-night effect on the solar neutrino flux it renders us a simple analytical expression, which is more accurate than those derived by using the perturbation theory and can be extended to higher energies.

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arXiv2006

Enhancing the Pierre Auger Observatory to the 10^{17} to 10^{18.5} eV Range: Capabilities of an Infill Surface Array

The Pierre Auger Observatory has been designed to study the highest-energy cosmic rays in nature (E > 10^{18.5} eV). The determination of their arrival direction, energy and composition is performed by the analysis of the atmospheric showers they produce. The Auger Surface Array will consist of 1600 water Cerenkov detectors placed in an equilateral triangular grid of 1.5 km spacing. The aim of this paper is to show that the addition of a "small" area of surface detectors at half or less the above mentioned spacing would allow a dramatic increase of the physical scope of this Observatory, reaching lower energies at which the transition from galactic to extragalactic sources is expected.

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