Presentaci

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Hybrid Extensive Air Shower Detector Array at
the University of Puebla to Study Cosmic Rays
O. MARTINEZ, H. SALAZAR, L. VILLASEÑOR Grupo
de Estudiantes   Facultad de Físico-Matemáticas,
Benemérita Universidad Autónoma de Puebla,
Apartado Postal 1364, Puebla, Pue., 72000,
México   On leave of absence from Institute of
Physics and Mathematics, University of Michoacan,
Morelia, Mich., 58040, México
EMA 05 Morelia July 18-22, 2005
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EAS Array
PMT Electron tubes 9353 K

• Area 4000 m2
• 10 Liquid Ssintillator Detectors (Bicron BC-517H)
• 4 Water Cherenkov Detectors

PMT EMI 9030 A
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• 2200m a.s.l., 800 g/cm2. Located at Campus
  Universidad Autonoma
• de Puebla
• Hybrid Liquid Scintillator Detectors and water
  Cherenkov Detectors
• Energy range 1014-
• 1016 eV

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DAQ System

• Trigger Coincidence of 4 central detectors
  (40mx40m)
• NIM y CAMAC.

• Uso digital Osciloscopes as ADCs.

• Rate 80 eventos/h

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Monitoring

• Use CAMAC scalers to measure rates of single
  partícles on each detector.
• Day-night variations lt10

s/mean around 3
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Calibration
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74 pe
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LabView based DAS
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MPV of EM peak 0.12 VEM i.e. around 29 MeV,
i.e., dominated By knock-on decay electrons
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Stopping muon at 0.1 VEM
Decay electron at 0.17 VEM 41 MeV
Crossing muon at 1 VEM
Alarcón M. et al., NIM A 420 1-2, 39-47
(1999).
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Data Analysis

• Arrival direction
• sinq sinf d/c(t2-t1)

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Angular distribution inferred directly from the
relative arrival times of shower front in good
agreement with the literature
cosp?? sen ?
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Data Analysis

• Lateral Distribution Functions

The shower core is located as the center of
gravity.

• Energy Determination

EAS-TOP, Astrop. Phys, 10(1999)1-9
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Ne, obtained for vertical showers. The fitted
curve is Ik (Ne/Nek) -g, gives g2.440.13
which corresponds to a spectral index of the
enerfy distributions of g2.6
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Muon/EM Separation
Muons deposit 240 MeV in 1.20m high water and
only 26 MeV in 13 cm high liquid, while electrons
deposit all of their energy i.e., around 10
MeV. Therefore for 10 Mev electrons we
expect Mu/EM24 for Cherenkov Mu/EM2.6 for
Liq. Scint.
Cherenkov
Liquid Scint
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Mass CompositionHybrid Array

Solution
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Iterations Start with Ne82,300 Nmu 32700 E0
233 TeV
Iterations End with Ne68000 Nmu 18200 E0
196 TeV
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Mass CompositionNon-Hybrid Array

Do a three parameter fit to

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Mass CompositionNon-Hybrid but Composite Array

• Two Identical types of Cherenkov Detectors one
  filled with 1.20 m of water and the other with
  0.60 m, i.e., VEMC0.5VEMC

i.e., do independent fits of rEM and rmuon to
NKG and Greissen LDF, respectively, where
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Conclusions
We have checked the stability and performed the
calibration of the detectors. We have measured
and analyzed the arrival direction of showers.
We determine the energy of the primary by
measuring the total number of charged particles
obtaining by integration of the fitted LDF.
Study of Muon/Electromagnetic ratio is underway