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Arreglo EAS-UAP para el Estudio de Rayos Cósmicos alrededor de 10 15 eV

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Arreglo EAS-UAP para el Estudio de Rayos Cósmicos alrededor de 10 15 eV. Humberto, Salazar, Oscar Martínez, César Alvarez, L. Villaseñor * + Estudiantes del Grupo de la FCFM-BUAP

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slide1

Arreglo EAS-UAP para el Estudio de Rayos Cósmicos alrededor de 1015 eV

Humberto, Salazar, Oscar Martínez, César Alvarez, L. Villaseñor* +

Estudiantes del Grupo de la FCFM-BUAP

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

Coloquio del Grupo de Altas Energías

CINVESTAV-IPN

D.F.

Sept. 20, 2005

slide10

At an energy of approximately3 PeVthe spectral index steepens (“knee”).

  • To understand thereason for the knee, one must understand thesource, acceleration mechanism, and propagationof cosmic rays.
  • First-order Fermiaccelerationhas a cutoff energy (protons to 1014 eV and Iron to 3 x 1015 eV)
  • Observing the mass composition of cosmicrays at the knee therefore provides an importantclue to the origin of cosmic rays.
slide11

Source

  • Supernova shock-wave Fermiacceleration is correct + Unknown mechanism i.e., rotating compact magnetic objects (neutron stars or black holes) at higher energies = kink due to overlap between the two mechanisms with progressive change in chemical composition as the knee is approached.

Propagation

  • Smooth energy distribution up to the highest cosmic-ray energies with unknown loss mechanism beginning at about 1015 eV.
  • Measuring the chemical composition of the cosmic rays at 1015 eV cantest the different explanations.
eas array

PMT Electron tubes 9353 K

EAS Array
  • Area: 4000 m^2
  • 10 Liquid Ssintillator Detectors (Bicron BC-517H)
  • 4 Water Cherenkov Detectors

PMT EMI 9030 A

slide13

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

3-4 central

detectors

(40mx40m)

NIM y CAMAC.

DAQ System
  • Use digital Osciloscopes
  • as ADCs.
  • Rate: 80 eventos/h
daq system1
CalibrationDAQ System
  • Rate: 250 events/m2/s
monitoring
Use CAMAC scalers to measure rates of single partícles on each detector.

Day-night variations <10%

Monitoring

s/mean around 3%

slide21

MPV of EM peak = 0.12 VEM

i.e. around 29 MeV, i.e., dominated

By knock-on + decay electrons

slide22

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).

slide23

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/EM=24 for Cherenkov

Mu/EM=2.6 for Liq. Scint.

Cherenkov

Liquid Scint

data analysis
Arrival direction

sinq sinf = d/c(t2-t1)

Data Analysis
slide25

Angular distribution inferred directly from

the relative arrival times of shower front

in good agreement with the literature:

cosp sen 

data analysis1
Lateral Distribution FunctionsData Analysis

The shower core is located as the center of gravity.

  • Energy Determination

EAS-TOP, Astrop. Phys,

10(1999)1-9

slide27

Ne, obtained for vertical showers. The fitted curve is Ik (Ne/Nek)-g, gives g=2.44±0.13 which corresponds to a spectral index of the enerfy distributions of g=2.6

slide28

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/EM=24 for Cherenkov

Mu/EM=2.6 for Liq. Scint.

Cherenkov

Liquid Scint

slide30

Iterations

Start with

Ne=82,300

Nmu = 32700

E0 = 233 TeV

Iterations

End with

Ne=68000

Nmu = 18200

E0 = 196 TeV

mass composition non hybrid array
Mass CompositionNon-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., VEMC’=0.5VEMCMass CompositionNon-Hybrid but Composite Array

i.e., do independent fits

of rEM and rmuon to NKG

and Greissen LDF,

respectively, where:

slide33

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:

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