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Ground Detectors for the Study of Cosmic Ray Showers
Luis Villaseor-UMSNH In coll. with the group of Humberto Salazar-
BUAP SECOND SCHOOL ON COSMIC RAYS AND ASTROPHYSICS Puebla, Mxico
September 7, 2006 Contents Single Liquid Scintillator (LS)
Detector
Single Water Cherenkov (WC) Detector Composition of showers with
known m/EM and use of neural networks Hybrid EAS-UAP Ground Array
to Study CRs with Energies around 1015 eV Conclusions Single Liquid
Scintillator (LS)
Detector 35 l liquid Scintillator + 2 inch PMT + simple electronics
1.3 million double-pulse events 2 MeV/cm I~ 1 cm-2 min-1 t1= t
=2.208 +- 0.027 ms t2= 1.979 +- 0.039 ms m+/m - =1.28 +-0.06
Gc = t2-1 - t1-1 = ms-1 m+/m - = Measurement of the lifetimes of
Pions and Kaons using this simple setup is (maybe) possible Single
Water Cherenkov (WC)
Detector Rotoplas Tank Inner D = 1.54 m 8 inch PMT 2200 l distilled
water up to 1.2 m (1/5 in volume of Auger tanks) Tyvek used as
inside liner Measure Charge, Amplitude,T10-50,T10-90
with good precision for three different triggers. Arbitrary muons
threshold of 30 mV ~74 pe LabView based DAS No PMT Glass Cherenkov
signal With PMT Glass Cherenkov signal No PMT Glass Cherenkov
signal With PMT Glass Cherenkov signal R shower (Q>7VEM) = 1
Hz
Low Charge Peak=0.12 VEM Rmuon = 876 Hz R EM = 80 Hz R shower
(Q>7VEM) = 1 Hz Not an Artifact due to V threshold = 0.12 VEM x
240 MeV/VEM = 29 MeV for knock-on electrons Shaded hist. shows
electrons selected for Q/A < .5 risetime < .5 With E~ 10.8
MeV Muon Decay in a WC Detector
Raw Data With cut C2 > C1 t = ms = 41 +- 11 MeV for decay
electrons Stopping muon at 0.95 VEM
Crossing muon at 1.05 VEM Alarcn M. et al., NIM A 420 [1-2], 39-47
(1999). Composition of showers with known m/EM and use of neural
networks Nm/Ne Strongly Correlated With Primary Mass, i.e. ~2 x for
Fe wrt p Look here To understand there Use low energy data to get
real
m and EM traces to eliminate systematics due to detector simulation
Look here To understand there Stopping muon or electron Q~0.12 VEM
(9 pe) T12~3ns Isolated Muon
Shower Q>7 VEM (500 pe) T12>15ns 4 muons, 15ns Data trace
Q=7.8 VEM 8 muons 15 ns 33 electrons 25 ns Parameters for Data and
Composed Events
Charge (VEM) Amplitude (V) T10-50 (ns) T10-90 2 or 3 classes as
output (8m, 4m + 33e, 66e)
Training and Clasification Results for a Kohonen Neural Network 4
features as input (Charge, Amplitude, T10-50, T1090) 8 Neurons in
first layer 4 in second layer 2 or 3 classesas output (8m, 4m +
33e, 66e) Training and Clasification Results for Two Classes
8 m 4m 33 e Data 65% 39% 68% 35% 61% 32% Class Training and
Clasification Results for Two Classes
8 m 0m 66 e Data 65% 33% 78% 35% 67% 22% Class Training and
Clasification Results for Three Classes
8 m 0 e 4 m 33 e 0m 66 e Data 56% 29% 33% 58% 21% 35% 27% 15% 0 m
23% 36% 40% Class Conclusions Clear separation of muons, electrons,
PMT interactions and showers in a single WCD Rise time 10-50% is
linear with Q/V Neural Networks classify composed events of muons
and electrons better than randomly Shower data is dominated by
muons To do: Apply to Auger with 25 ns sampling time. EAS-UAP
Ground Array to Study CRs with Energies around 1015 eV
in coll. WithBUAP: Humberto Salazar, Oscar Martnez, Csar Alvarez +
Estudiantes del Grupo de la FCFM-BUAP Facultad deFsico-Matemticas,
Benemrita Universidad Autnoma de Puebla, Apartado Postal 1364,
Puebla, Pue., 72000, Mxico At an energy of approximately 3 PeV the
spectral index steepens (knee).
To understand the reason for the knee, one must understand the
source, acceleration mechanism, and propagation of cosmic rays.
First-order Fermi acceleration has a cutoff energy (protons to 1014
eV and Iron to 3 x 1015 eV) Observing the mass composition of
cosmic rays at the knee therefore provides an important clue to the
origin of cosmic rays. Source Supernova shock-wave Fermi
acceleration 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
can test the different explanations. PMT Electron tubes 9353 K EAS
Array(19 N, 90W, 800 g/cm2)Goal:Study energy spectrum, arrival
direction and compositin of CRs around the knee: from eV. Area:
4000 m^2 10 Liquid Ssintillator Detectors (Bicron BC-517H) 4 Water
Cherenkov Detectors 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 EAS-UAP Control Room
Home-made DAQ electronics under construction DAQ System Use digital
Osciloscopes as ADCs. Rate: 80 eventos/h
Trigger: Coincidence of 3-4 central detectors (40mx40m) NIM y
CAMAC. Use digital Osciloscopes as ADCs. Rate: 80 eventos/h DAQ
System Calibration Rate: 250 events/m2/s Monitoring Use CAMAC
scalers to measure rates of single partcles on each detector.
Day-night variations