ESAF is the simulation and analysis software framework developed for the EUSO experiment. ESAF's scope is the whole process of data simulations and data-analysis, from the primary particle interaction in atmosphere to the reconstruction of the event. Based on the ROOT package and designed using Object Oriented technology, ESAF is organized in two main programs: the full montecarlo simulation and the reconstruction framework. The former includes all the relevant physical contributions, shower development in atmosphere, light transport to the detector pupil and detector response, while the latter comprises basic data cleaning, track direction, shower profile and energy reconstruction algorithms. Here we describe the software architecture and its main features

Bottai, S.

Bérat, C.

Catalano, O.

D'Ali Staiti, G.

Dolbeau, J.

Maccarone, M.C.

Moreggia, S.

Naumov, D.

Pallavicini, M.

Pesce, R.

Petrolini, A.

Plagnol, E.

Stutz, A.

Taddei, E.

Thea, A.

d'Ali Staiti, G.

HAL-IN2P3

The EUSO simulation and analysis frameworkA. Thea, C. Be´rat, S. Bottai, O. Catalano, G. D’Ali Staiti, J. Dolbeau, M.C.Maccarone, S. Moreggia, D. Naumov, M. Pallavicini, et al.To cite this version:A. Thea, C. Be´rat, S. Bottai, O. Catalano, G. D’Ali Staiti, et al.. The EUSO simulation andanalysis framework. 29th International Cosmic Ray Conference (ICRC 2005), Aug 2005, Pune,India. pp.133-136, 2005. <in2p3-00025585>HAL Id: in2p3-00025585http://hal.in2p3.fr/in2p3-00025585Submitted on 8 Feb 2006HAL is a multi-disciplinary open accessarchive for the deposit and dissemination of sci-entific research documents, whether they are pub-lished or not. The documents may come fromteaching and research institutions in France orabroad, or from public or private research centers.L’archive ouverte pluridisciplinaire HAL, estdestine´e au de´poˆt et a` la diffusion de documentsscientifiques de niveau recherche, publie´s ou non,e´manant des e´tablissements d’enseignement et derecherche franc¸ais ou e´trangers, des laboratoirespublics ou prive´s.29th International Cosmic Ray Conference Pune (2005) 00, 101104The Euso Simulation and Analysis FrameworkA. Thea , C. Berat, S. Bottai, O. Catalano, G. D’Ali Staiti  , J. Dolbeau,M.C. Maccarone, S. Moreggia, D. Naumov, M. Pallavicini , R. Pesce , A. Petrolini ,E. Plagnol, A. Stutzand E. Taddei.(a) INFN and Universita di Genova, Italy(b) INFN and Universita Sezione di Firenze, Italy(c) Laboratoire de Physique Subatomique et de Cosmologie, Grenoble, France(d) ApC, Paris, France(e) Universita di Palermo, Italy(f) Istituto Nazionale di Astrosica (INAF/IASF) - Sezione di Palermo, ItalyPresenter: A.Thea (thea@ge.infn.it), ita-thea-A-abs2-he15-posterESAF is the simulation and analysis software framework developed for the EUSO experiment. ESAF’s scopeis the whole process of data simulations and data-analysis, from the primary particle interaction in atmosphereto the reconstruction of the event. Based on the ROOT package and designed using Object Oriented technology,ESAF is organized in two main programs: the full montecarlo simulation and the reconstruction framework.The former includes all the relevant physical contributions, shower development in atmosphere, light transportto the detector pupil and detector response, while the latter comprises basic data cleaning, track direction,shower profile and energy reconstruction algorithms. Here we describe the software architecture and its mainfeatures.IntroductionThe experiments aiming to study Extensive Air Showers (EAS) generated in the atmosphere by Ultra HighEnergy Cosmic Radiation with energy above 	 eV require detectors with huge target.In order to achieve a larger geometrical aperture an alternative and complementary approach to ground basedexperiment has been proposed for the first time by John Linsley more than 20 years ago. An EAS can bedetected by observing the fluorescence light emitted by atmospheric nitrogen. In fact, instead of looking atthis UV light from ground, the same signal can be watched from above, using a space-borne telescope onorbit around the earth. The fluorescence light is produced isotropically and, at any depth in the shower, isproportional to the number of charged particles.The ”Extreme Universe Space Observatory - EUSO” [1] was proposed as free-flier satellite in winter 1999.EUSO was accepted for an Accommodation Study on the ISS (end 2000) and then approved for Phase A(study report and conceptual design), successfully completed in summer 2004.ESAF, the EUSO Simulation and Analysis Framework, has been developed during the EUSO Phase A studyas the full End-to-end simulation and analysis chain, from the simulation of the primary particle interaction inatmosphere, to the transport of light to the EUSO optical pupil, to the detector response simulation and finallyto the reconstruction and the physical analysis. We designed ESAF so that each one of the above steps couldbe run individually and independently from the other ones. With this approach it is possible to run the samereconstruction and analysis code for the real data and for the simulated ones. Moreover, it is also possible torun single parts of this chain and check quantitatively the differences between different configurations of thedetector or different approximations for the physical processes involved. Therefore ESAF is easily adaptableto any space-borne detector design.ESAF consists of a simulation package and a reconstruction package, is written in C++ and based on the ROOT102 A.Thea et al.[3] framework. ESAF is designed following the general guidelines of the Object Oriented programming, thatprovide the required degree of flexibility and modularity.The simulation has been structured in two main subsystems, the light generation, encapsulating all the physicalphenomena occurring outside EUSO that can produce photons on the entrance of the detector, and the detector,where the photons are traced through the telescope and the electronics response is simulated.The ROOT file format has been chosen for the output of the simulation. Each event in the ROOT file containsdetailed information of each simulated effect along with the detector configuration used. To inspect the resultsa set of detailed event viewers for every step in the simulation chain have been implemented (fig:1). The ROOTfile acts also as interface between the simulation and the reconstruction.The reconstruction is designed as framework and a set of modules that will reconstruct the event. Each modulehas a specific task, that can actually be picked by the user and included in the reconstruction chain build by theframework.The light generationThe detected shower signal depends critically on the atmospheric parameters. The monitored volume of atmo-sphere is continuously and rapidly changing, it spans many degrees in latitude and characterized by stronglyvariable weather conditions. Clouds may affect and distort or even enhance the shower signal. Also, manydifferent kind of backgrounds are expected, including night-glow, man-made lights, lightnings, reflected moon-light.X [mm]480 500 520 540 560 580 600 620 640Y [mm]480500520540560580600620640Counts051015202530s]Time [1550 1600 1650 1700 1750 1800photonsN050100150200250300350400450Photon distributions versus timeScatteredCerenkovFluorescenceFigure 1. Front-end counts, generated by a eV proton shower developing in clear skyatmosphere, on the EUSO focal surface. The nightglow background hits are not shown.Figure 2. Number of photons reaching the EUSO pupilversus time. The different contributions are shown.The simulation of light toward the detector has been divided in three steps: the physics event generation, theproduction of light and the transport of light through the atmosphere. These steps are independent, allowingthe user to test and compare different shower models, or fluorescence emission in the same structure.1. Several shower generators have been implemented, both as integrated part of ESAF (UNISIM [4]) oras interfaces to well established stand-alone generators (SLAST[5] and Corsika[6]). Lightnings andMeteors generators are foreseen.The EUSO Simulation and Analysis Framework 1032. The description of the physical event is given to the light source module to be converted into photons.Shower’s fluorescence and ﬀﬁerenkov signal spectra are simulated according the local atmosphere andelectrons distributions. Nitrogen fluorescence yield data by Kakimoto[7] and Nagano[8] are used.3. Eventually the photons are propagated from the creation point to the pupil of the detector by the radia-tive transfer module. Nitrogen fluorescence and ﬀﬁerenkov radiation are treated separately. The former,isotropic, is transmitted directly to the detector, the latter, strongly forward beamed, is scattered in theair and diffusely reflected by the earth surface or clouds at the impact point (fig.2). Transmission coeffi-cients are computed for each wavelength as a function of the local atmosphere using the LOWTRAN[9]package. The radiative transfer module supports several atmospheric models (US Standard, Lowtran,Corsika) and MSISE. The MSISE models, that depends on geodetic position (Lat. and Longitude), isparticularly important for an earth-orbiting detector studies. The reflection of ﬀﬁerenkov light on simpleuniform cloud layers has been implemented.Shower Zenith Angle [deg]0 10 20 30 40 50 60 70 80 90Number of p.e.5001000150020002500 eV)20 10× (1.0 θ v.s. p.e.NSignal+BackgroundSignalBackgroundShower Zenith Angle [deg]0 10 20 30 40 50 60 70 80 90Number of p.e.4681012141618 eV)20 10× (1.0 θ v.s. p.e.Max NSignal+BackgroundSignalBackground(a) (b)Figure 3. (a) Number of counts on the EUSO focal surface generated by ﬂ eV showers as a function of the showerzenith angle. (b) Number of counts in the most populated pixel on EUSO focal surface as a function of shower zenithangle. EUSO Redbook requirements conguration was used. Background counts are limited to the pixel with signal.The detectorThe instrument must collect as many photons as possible, in order to be able to detect the faint signal from theless energetic EAS and to discriminate it from the background. All the components must be carefully assembledto minimize any possible signal loss. Dead areas on the focal surface, optics design, fluctuations in photodetectors response, background rate dependence on the position on the focal surface affect the performancesof the instrument if not correctly taken into account. The role of the detector’s simulation is twofold:1. Support a full Monte Carlo simulation of the advanced instrument design. Currently, EUSO Phase Aconfiguration has been successfully implemented: Large field of view Fresnel optical system, modularfocal surface design, photo sensors assembled in 2x2 elementary cells (fig. 1 ). All sensors are suppliedwith an UV bandpass optical filter and each elementary cell is connected to its own front-end chip.Elementary cells are grouped into logical triggering units (macrocells) and several first level triggerpatterns based on the space-time coherence of the shower signal has been included.104 A.Thea et al.2. Provide a fast and reliable tool to simulate a parameterized detector. The possibility to test the responseas a function of optics field of view, optics transmittance, point spread function, photo detector pixelsize and many other parameters is fundamental for any feasibility study of future space-borne UHECRdetectors.ReconstructionBecause of the small number of detected photons (fig. 3a and 3b), the reconstruction of the features EAS andthen the primary particle parameters is very tricky, especially at the lower energies ( ﬃ	 eV). The showerimage on the focal plane must be located according to the trigger information, cleaned up from the backgroundand then analyzed. The core of the reconstruction is the modular framework. Every task of the reconstructionchain is a module. Many tasks have been implemented using different algorithms to find the most suitable androbust one.Pattern recognition : Disentangling of the signal from the incoherent background is committed to the Houghtransform and clustering algorithms.Track finding : The EAS develops in the atmosphere at the speed of light. Using this information, its directionin space can be computed from the 2-dim. image on the focal surface. Several robust numerical andanalytical approaches have been implemented.Energy : The primary particle energy is, in principle, proportional to the number of detected photo electrons.Nevertheless many effects can lead to a wrong estimation, if not taken into account. The energy mod-ule uses the information on atmosphere optical depth, detector’s optics and focal surface dead areas torecover the shower longitudinal profile and then extrapolate the initial energy.ConclusionsESAF is a stable, powerful and flexible simulation and reconstruction tool for UHECR space-based UV tele-scopes. Thanks to its flexibility, it will also play a key role in feasibility studies for future experiment proposalswithin the ESA Cosmic Vision 2015-2025 program.References[1] G. D’Alı`Staiti, “EUSO A Space mission searching for Extreme Energy Cosmic Rays and neutrinos”,Proceedings of the CRIS 2004 Conference, Catania, Italy, May 31 - June 4 2004[2] EUSO collaboration, this conference, several contributions.[3] ROOT Homepage, http://root.cern.ch/[4] Bottai S. 2001, Proc. of the 27th ICRC, Hamburg.[5] Naumov D. 2003, EUSO Report SDA-REP-015.[6] Heck D. et al.. 1998, Report FZKA6019, Forschungszentrum Karlsruhe[7] F. Kakimoto et al., NIM A372 (1996) 527.[8] M. Nagano et al., Astropart. Phys. 22 (2004) 235-248.[9] Kneizys F.X. et al. 1996,The MODTRAN 2/3 Report and LOWTRAN 7 MODEL, ed. L.W.Abreu andG.P. Anderson

The EUSO simulation and analysis framework

Hal-Diderot

The EUSO simulation and analysis framework
A. Thea, C. Be´rat, S. Bottai, O. Catalano, G. D’Ali Staiti, J. Dolbeau, M.C.
Maccarone, S. Moreggia, D. Naumov, M. Pallavicini, et al.
To cite this version:
A. Thea, C. Be´rat, S. Bottai, O. Catalano, G. D’Ali Staiti, et al.. The EUSO simulation and
analysis framework. 29th International Cosmic Ray Conference (ICRC 2005), Aug 2005, Pune,
India. pp.133-136, 2005. <in2p3-00025585>
HAL Id: in2p3-00025585
http://hal.in2p3.fr/in2p3-00025585
Submitted on 8 Feb 2006
HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.
L’archive ouverte pluridisciplinaire HAL, est
destine´e au de´poˆt et a` la diffusion de documents
scientifiques de niveau recherche, publie´s ou non,
e´manant des e´tablissements d’enseignement et de
recherche franc¸ais ou e´trangers, des laboratoires
publics ou prive´s.
29th International Cosmic Ray Conference Pune (2005) 00, 101104
The Euso Simulation and Analysis Framework
A. Thea
 
, C. Berat

, S. Bottai

, O. Catalano

, G. D’Ali Staiti  , J. Dolbeau

,
M.C. Maccarone

, S. Moreggia

, D. Naumov

, M. Pallavicini
 
, R. Pesce
 
, A. Petrolini
 
,
E. Plagnol

, A. Stutz

and E. Taddei

.
(a) INFN and Universita di Genova, Italy
(b) INFN and Universita Sezione di Firenze, Italy
(c) Laboratoire de Physique Subatomique et de Cosmologie, Grenoble, France
(d) ApC, Paris, France
(e) Universita di Palermo, Italy
(f) Istituto Nazionale di Astrosica (INAF/IASF) - Sezione di Palermo, Italy
Presenter: A.Thea (thea@ge.infn.it), ita-thea-A-abs2-he15-poster
ESAF is the simulation and analysis software framework developed for the EUSO experiment. ESAF’s scope
is the whole process of data simulations and data-analysis, from the primary particle interaction in atmosphere
to the reconstruction of the event. Based on the ROOT package and designed using Object Oriented technology,
ESAF is organized in two main programs: the full montecarlo simulation and the reconstruction framework.
The former includes all the relevant physical contributions, shower development in atmosphere, light transport
to the detector pupil and detector response, while the latter comprises basic data cleaning, track direction,
shower profile and energy reconstruction algorithms. Here we describe the software architecture and its main
features.
Introduction
The experiments aiming to study Extensive Air Showers (EAS) generated in the atmosphere by Ultra High
Energy Cosmic Radiation with energy above 
	 eV require detectors with huge target.
In order to achieve a larger geometrical aperture an alternative and complementary approach to ground based
experiment has been proposed for the first time by John Linsley more than 20 years ago. An EAS can be
detected by observing the fluorescence light emitted by atmospheric nitrogen. In fact, instead of looking at
this UV light from ground, the same signal can be watched from above, using a space-borne telescope on
orbit around the earth. The fluorescence light is produced isotropically and, at any depth in the shower, is
proportional to the number of charged particles.
The ”Extreme Universe Space Observatory - EUSO” [1] was proposed as free-flier satellite in winter 1999.
EUSO was accepted for an Accommodation Study on the ISS (end 2000) and then approved for Phase A
(study report and conceptual design), successfully completed in summer 2004.
ESAF, the EUSO Simulation and Analysis Framework, has been developed during the EUSO Phase A study
as the full End-to-end simulation and analysis chain, from the simulation of the primary particle interaction in
atmosphere, to the transport of light to the EUSO optical pupil, to the detector response simulation and finally
to the reconstruction and the physical analysis. We designed ESAF so that each one of the above steps could
be run individually and independently from the other ones. With this approach it is possible to run the same
reconstruction and analysis code for the real data and for the simulated ones. Moreover, it is also possible to
run single parts of this chain and check quantitatively the differences between different configurations of the
detector or different approximations for the physical processes involved. Therefore ESAF is easily adaptable
to any space-borne detector design.
ESAF consists of a simulation package and a reconstruction package, is written in C++ and based on the ROOT
102 A.Thea et al.
[3] framework. ESAF is designed following the general guidelines of the Object Oriented programming, that
provide the required degree of flexibility and modularity.
The simulation has been structured in two main subsystems, the light generation, encapsulating all the physical
phenomena occurring outside EUSO that can produce photons on the entrance of the detector, and the detector,
where the photons are traced through the telescope and the electronics response is simulated.
The ROOT file format has been chosen for the output of the simulation. Each event in the ROOT file contains
detailed information of each simulated effect along with the detector configuration used. To inspect the results
a set of detailed event viewers for every step in the simulation chain have been implemented (fig:1). The ROOT
file acts also as interface between the simulation and the reconstruction.
The reconstruction is designed as framework and a set of modules that will reconstruct the event. Each module
has a specific task, that can actually be picked by the user and included in the reconstruction chain build by the
framework.
The light generation
The detected shower signal depends critically on the atmospheric parameters. The monitored volume of atmo-
sphere is continuously and rapidly changing, it spans many degrees in latitude and characterized by strongly
variable weather conditions. Clouds may affect and distort or even enhance the shower signal. Also, many
different kind of backgrounds are expected, including night-glow, man-made lights, lightnings, reflected moon-
light.
X [mm]
480 500 520 540 560 580 600 620 640
Y 
[m
m]
480
500
520
540
560
580
600
620
640
Co
un
ts
0
5
10
15
20
25
30
s]Time [
1550 1600 1650 1700 1750 1800
ph
o
to
n
s
N
0
50
100
150
200
250
300
350
400
450
Photon distributions versus time
Scattered
Cerenkov
Fluorescence
Figure 1. Front-end counts, generated by a
 
eV proton shower developing in clear sky
atmosphere, on the EUSO focal surface. The night
glow background hits are not shown.
Figure 2. Number of photons reaching the EUSO pupil
versus time. The different contributions are shown.
The simulation of light toward the detector has been divided in three steps: the physics event generation, the
production of light and the transport of light through the atmosphere. These steps are independent, allowing
the user to test and compare different shower models, or fluorescence emission in the same structure.
1. Several shower generators have been implemented, both as integrated part of ESAF (UNISIM [4]) or
as interfaces to well established stand-alone generators (SLAST[5] and Corsika[6]). Lightnings and
Meteors generators are foreseen.
The EUSO Simulation and Analysis Framework 103
2. The description of the physical event is given to the light source module to be converted into photons.
Shower’s fluorescence and ﬀ
ﬁ
erenkov signal spectra are simulated according the local atmosphere and
electrons distributions. Nitrogen fluorescence yield data by Kakimoto[7] and Nagano[8] are used.
3. Eventually the photons are propagated from the creation point to the pupil of the detector by the radia-
tive transfer module. Nitrogen fluorescence and ﬀ
ﬁ
erenkov radiation are treated separately. The former,
isotropic, is transmitted directly to the detector, the latter, strongly forward beamed, is scattered in the
air and diffusely reflected by the earth surface or clouds at the impact point (fig.2). Transmission coeffi-
cients are computed for each wavelength as a function of the local atmosphere using the LOWTRAN[9]
package. The radiative transfer module supports several atmospheric models (US Standard, Lowtran,
Corsika) and MSISE. The MSISE models, that depends on geodetic position (Lat. and Longitude), is
particularly important for an earth-orbiting detector studies. The reflection of ﬀ
ﬁ
erenkov light on simple
uniform cloud layers has been implemented.
Shower Zenith Angle [deg]
0 10 20 30 40 50 60 70 80 90
N
um
be
r o
f p
.e
.
500
1000
1500
2000
2500
 eV)20 10× (1.0 θ v.s. p.e.N
Signal+Background
Signal
Background
Shower Zenith Angle [deg]
0 10 20 30 40 50 60 70 80 90
N
um
be
r o
f p
.e
.
4
6
8
10
12
14
16
18
 eV)20 10× (1.0 θ v.s. p.e.Max N
Signal+Background
Signal
Background
(a) (b)
Figure 3. (a) Number of counts on the EUSO focal surface generated by ﬂ eV showers as a function of the shower
zenith angle. (b) Number of counts in the most populated pixel on EUSO focal surface as a function of shower zenith
angle. EUSO Redbook requirements conguration was used. Background counts are limited to the pixel with signal.
The detector
The instrument must collect as many photons as possible, in order to be able to detect the faint signal from the
less energetic EAS and to discriminate it from the background. All the components must be carefully assembled
to minimize any possible signal loss. Dead areas on the focal surface, optics design, fluctuations in photo
detectors response, background rate dependence on the position on the focal surface affect the performances
of the instrument if not correctly taken into account. The role of the detector’s simulation is twofold:
1. Support a full Monte Carlo simulation of the advanced instrument design. Currently, EUSO Phase A
configuration has been successfully implemented: Large field of view Fresnel optical system, modular
focal surface design, photo sensors assembled in 2x2 elementary cells (fig. 1 ). All sensors are supplied
with an UV bandpass optical filter and each elementary cell is connected to its own front-end chip.
Elementary cells are grouped into logical triggering units (macrocells) and several first level trigger
patterns based on the space-time coherence of the shower signal has been included.
104 A.Thea et al.
2. Provide a fast and reliable tool to simulate a parameterized detector. The possibility to test the response
as a function of optics field of view, optics transmittance, point spread function, photo detector pixel
size and many other parameters is fundamental for any feasibility study of future space-borne UHECR
detectors.
Reconstruction
Because of the small number of detected photons (fig. 3a and 3b), the reconstruction of the features EAS and
then the primary particle parameters is very tricky, especially at the lower energies ( ﬃ	 eV). The shower
image on the focal plane must be located according to the trigger information, cleaned up from the background
and then analyzed. The core of the reconstruction is the modular framework. Every task of the reconstruction
chain is a module. Many tasks have been implemented using different algorithms to find the most suitable and
robust one.
Pattern recognition : Disentangling of the signal from the incoherent background is committed to the Hough
transform and clustering algorithms.
Track finding : The EAS develops in the atmosphere at the speed of light. Using this information, its direction
in space can be computed from the 2-dim. image on the focal surface. Several robust numerical and
analytical approaches have been implemented.
Energy : The primary particle energy is, in principle, proportional to the number of detected photo electrons.
Nevertheless many effects can lead to a wrong estimation, if not taken into account. The energy mod-
ule uses the information on atmosphere optical depth, detector’s optics and focal surface dead areas to
recover the shower longitudinal profile and then extrapolate the initial energy.
Conclusions
ESAF is a stable, powerful and flexible simulation and reconstruction tool for UHECR space-based UV tele-
scopes. Thanks to its flexibility, it will also play a key role in feasibility studies for future experiment proposals
within the ESA Cosmic Vision 2015-2025 program.
References
[1] G. D’Alı`Staiti, “EUSO A Space mission searching for Extreme Energy Cosmic Rays and neutrinos”,
Proceedings of the CRIS 2004 Conference, Catania, Italy, May 31 - June 4 2004
[2] EUSO collaboration, this conference, several contributions.
[3] ROOT Homepage, http://root.cern.ch/
[4] Bottai S. 2001, Proc. of the 27th ICRC, Hamburg.
[5] Naumov D. 2003, EUSO Report SDA-REP-015.
[6] Heck D. et al.. 1998, Report FZKA6019, Forschungszentrum Karlsruhe
[7] F. Kakimoto et al., NIM A372 (1996) 527.
[8] M. Nagano et al., Astropart. Phys. 22 (2004) 235-248.
[9] Kneizys F.X. et al. 1996,The MODTRAN 2/3 Report and LOWTRAN 7 MODEL, ed. L.W.Abreu and
G.P. Anderson


A. Thea

C. Berat

S. Bottai

O. Catalano

G. D. Staiti

J. Dolbeau

M. C. Maccarone

S. Moreggia

D. Naumov

PALLAVICINI, MARCO

R. Pesce

PETROLINI, ALESSANDRO

E. Plagnol

A. Stutz

E. Taddei

Archivio istituzionale della ricerca - Università di Genova

Hal - Université Grenoble Alpes

HAL-OBSPM

HAL-CEA

http://hal.in2p3.fr/in2p3-00025585/document

The EUSO simulation and analysis framework

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