Ground Detectors for the Study of Cosmic Ray Showers Luis Villaseñor-UMSNH In coll. with the group of Humberto Salazar- BUAP SECOND SCHOOL ON COSMIC RAYS AND ASTROPHYSICS Puebla, México 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 = 0.050.01 ms-1 m+/m - =1.28 +-0.06

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 R muon = 876 Hz R EM = 80 Hz R shower (Q>7VEM) = 1 Hz Not an Artifact due to V threshold

<E> = 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 = 2.08 +- .12ms

<E> = 41 +- 11 MeV for decay electrons Stopping muon at 0.95 VEM Crossing muon at 1.05 VEM Alarcón 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) 7.9+-0.5 8.0+-0.55 7.9+-0.51 8.34+-0.4 Amplitude (V) 1.16+-0.08 1.20+-0.20 1.25+-0.20 1.34+-0.19 T10-50 (ns) 16.7+-0.9 17.5+-3.0 18.25+-3.6 18.45+-2.9 T10-90 50.8+-2.0 50.0+-4.3 52.4+-6.6 54.2+-6.9

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 classes as 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. With BUAP: Humberto Salazar, Oscar Martínez, César Alvarez + Estudiantes del Grupo de la FCFM-BUAP   Facultad de Físico-Matemáticas, Benemérita Universidad Autónoma de Puebla, Apartado Postal 1364, Puebla, Pue., 72000, México

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 (19º N, 90ºW, 800 g/cm2) Goal: Study energy spectrum, arrival direction and compositión of CRs around the knee: from 1014 - 1016 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 partícles on each detector. Day-night variations <10% s/mean around 3%

Monitoring and Calibration

Calibration

Calibration

MC Simulations using Aires Algorithm for Locating the Shower Core

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

Arrival direction x01 sinq cosf = c(t1-t0) / x01 sinq sinf = c(t2-t0) / y02 y02 For this event q = 23.0 of = 224.9 o (LS) q = 21.1 o f = 227.8 o (WC)

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

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

Ne, obtained for vertical showers 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

Mass Composition Hybrid Array Solution:

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 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’=0.5VEMC i.e., do independent fits of rEM and rmuon to NKG and Greissen LDF, respectively, where:

Conclusions for the EAS-UAP 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 CR by measuring the total number of charged particles obtained by integration of the fitted LDF. Study of Muon/Electromagnetic ratio is underway: