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Register a new userLateral density and arrival time distributions of Cherenkov photons in extensive air showers: a simulation study
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Umananda Dev Goswami
Publication date
2014
fields
Physics
and research's language is
English
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We have investigated some features of the density and arrival time distributions of Cherenkov photons in extensive air showers using the CORSIKA simulation package. The main thrust of this study is to see the effect of hadronic interaction models on the production pattern of Cherenkov photons with respect to distance from the shower core. Such studies are very important in ground based $gamma$-ray astronomy for an effective rejection of huge cosmic ray background, where the atmospheric Cherenkov technique is being used extensively within the energy range of some hundred GeV to few TeV. We have found that for all primary particles, the density distribution patterns of Cherenkov photons follow the negative exponential function with different coefficients and slopes depending on the type of primary particle, its energy and the type of interaction model combinations. Whereas the arrival time distribution patterns of Cherenkov photons follow the function of the form $t (r) = t_{0}e^{Gamma/r^{lambda}}$, with different values of the function parameters. There is no significant effect of hadronic interaction model combinations on the density and arrival time distributions for the $gamma$-ray primaries. However, for the hadronic showers, the effects of the model combinations are significant under different conditions.
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The simulation of Cherenkov photons lateral density and arrival time distributions in Extensive Air Showers (EASs) was performed with the CORSIKA code in the energy range: 100 GeV to 100 TeV. On the basis of this simulation we obtained a set of approximating functions for the primary $gamma$-ray photons, protons and iron nuclei incident at zenith angles from 0$^circ$ to 40$^circ$ over different altitudes of observation. Such a parameterisation is important for the primary particle identification, for the reconstruction of the shower observables and hence for a more efficient disentanglement of the $gamma$-ray showers from the hadronic showers. From our parameterisation analysis, we have found that even though the geometry of the lateral density ($rho_{ch}$) and the arrival time ($t_{ch}$) distributions is different for different primaries at a particular energy ($E$), at a particular incident angle ($theta$) and at a particular altitude of observation ($H$) up to a given distance from the showe core ($R$), the distributions follow the same mathematical functions $rho(E,R,theta,H) = a E^{b}exp[-{c R + (theta /d)^{2}-f H}]$ and $t(E,R,theta,H) = l E^{-m}exp(n/R^{p})({theta}^q+s)(u {H}^2+v)$ respectively but with different values of function parameters.
Future detection of Extensive Air Showers (EAS) produced by Ultra High Energy Cosmic Particles (UHECP) by means of space based fluorescence telescopes will open a new window on the universe and allow cosmic ray and neutrino astronomy at a level that is virtually impossible for ground based detectors. In this paper we summarize the results obtained in the context of the EUSO project by means of a detailed Monte Carlo simulation of all the physical processes involved in the fluorescence technique, from the Extensive Air Shower development to the instrument response. Particular emphasis is given to modeling the light propagation in the atmosphere and the effect of clouds. Main results on energy threshold and resolution, direction resolution and Xmax determination are reported. Results are based on EUSO telescope design, but are also extended to larger and more sensitive detectors.
As of 2023, the Square Kilometre Array will constitute the worlds largest radio telescope, offering unprecedented capabilities for a diverse science programme in radio astronomy. At the same time, the SKA will be ideally suited to detect extensive air showers initiated by cosmic rays in the Earths atmosphere via their radio emission. With its very dense and uniform antenna spacing in a fiducial area of one km$^2$ and its large bandwidth of 50-350 MHz, the low-frequency part of the SKA will provide very precise measurements of individual cosmic ray air showers. These precision measurements will allow detailed studies of the mass composition of cosmic rays in the energy region of transition from a Galactic to an extragalactic origin. Also, the SKA will facilitate three-dimensional tomography of the electromagnetic cascades of air showers, allowing the study of particle interactions at energies beyond the reach of the LHC. Finally, studies of possible connections between air showers and lightning initiation can be taken to a new level with the SKA. We discuss the science potential of air shower detection with the SKA and report on the technical requirements and project status.
We have studied the distribution patterns of lateral density, arrival time and angular position of Cherenkov photons generated in Extensive Air Showers (EASs) initiated by $gamma$-ray, proton and iron primaries incident with various energies and at various zenith angles. This study is the extension of our earlier work cite{Hazarika} to cover a wide energy range of ground based $gamma$-ray astronomy with a wide range of zenith angles ($le 40^circ$) of primary particles, as well as the extension to study the angular distribution patterns of Cherenkov photons in EASs. This type of study is important for distinguishing the $gamma$-ray initiated showers from the hadronic showers in the ground based $gamma$-ray astronomy, where Atmospheric Cherenkov Technique (ACT) is being used. Importantly, such study gives an insight on the nature of $gamma$-ray and hadronic showers in general. In this work, the CORSIKA 6.990 simulation code is used for generation of EASs. Similarly to the case of Ref.cite{Hazarika}, this study also revealed that, the lateral density and arrival time distributions of Cherenkov photons vary almost in accordance with the functions: $rho_{ch}(r) = rho_{0};e^{-beta r}$ and $t_{ch}(r) = t_{0}e^{Gamma/r^{lambda}}$ respectively by taking different values of the parameters of functions for the type, energy and zenith angle of the primary particle. The distribution of Cherenkov photons angular positions with respect to shower axis shows distinctive features depending on the primary type, its energy and the zenith angle.
Event-by-event measured arrival time distributions of Extensive Air Shower (EAS) muons are affected and distorted by various interrelated effects which originate from the time resolution of the timing detectors, from fluctuations of the reference time and the number (multiplicity) of detected muons spanning the arrival time distribution of the individual EAS events. The origin of these effects is discussed, and different correction procedures, which involve detailed simulations, are proposed and illustrated. The discussed distortions are relevant for relatively small observation distances (R < 200 m) from the EAS core. Their significance decreases with increasing observation distance and increasing primary energies. Local arrival time distributions which refer to the observed arrival time of the first local muon prove to be less sensitive to the mass of the primary. This feature points to the necessity of arrival time measurements with additional information on the curvature of the EAS disk.
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