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

EAS Array  Area: 4000 m^2  10 Liquid Ssintillator Detectors (Bicron BC-517H)  4 Water Cherenkov Detectors PMT Electron tubes 9353 K PMT EMI 9030 A

2200m a.s.l., 800 g/cm2. Located at Campus Universidad Autonoma de Puebla Hybrid: Liquid Scintillator Detectors and water Cherenkov Detectors Energy range 10^14- 10^16 eV

DAQ System Trigger: Coincidence of 4 central detectors (40mx40m) NIM y CAMAC. Uso digital Osciloscopes as ADCs. Rate: 80 eventos/h

Monitoring Use CAMAC scalers to measure rates of single partícles on each detector. Day-night variations <10%  /mean around 3%

Calibration

~74 pe

LabView based DAS

MPV of EM peak = 0.12 VEM i.e. around 29 MeV, i.e., dominated By knock-on + decay electrons

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], (1999).

Data Analysis Arrival direction sin  sin  = d/c(t 2 -t 1 )

Angular distribution inferred directly from the relative arrival times of shower front in good agreement with the literature: cos p  sen 

Data Analysis Lateral Distribution Functions Energy Determination EAS-TOP, Astrop. Phys, 10(1999)1-9 The shower core is located as the center of gravity.

N e, obtained for vertical showers. The fitted curve is I k (N e /N ek ) - , gives  =2.44±0.13 which corresponds to a spectral index of the enerfy distributions of  =2.6

Cherenkov Liquid Scint 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/EM=24 for Cherenkov Mu/EM=2.6 for Liq. Scint. Muon/EM Separation

Mass Composition Hybrid Array Solution:

Iterations Start with Ne=82,300 Nmu = E0 = 233 TeV Iterations End with Ne=68000 Nmu = E0 = 196 TeV

Mass Composition Non-Hybrid Array Do a three parameter fit to :

Mass Composition Non-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., VEM C’ =0.5VEM C i.e., do independent fits of  EM and  muon to NKG and Greissen LDF, respectively, where:

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: