1. 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

2. 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

3. Single Liquid Scintillator (LS)
Detector

5. 35 l liquid
Scintillator +
2 inch PMT +
simple electronics

6. 1.3 million
double-pulse events
2 MeV/cm
I ~ 1 cm-2 min-1

9. 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 - =

10. Measurement of
the lifetimes of
Pions and
Kaons
using this simple
setup
is (maybe)
possible

11. Single Water Cherenkov (WC)
Detector

12. 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

13. Measure Charge, Amplitude,T10-50,T10-90
with good precision for three different triggers.
Arbitrary muons threshold of 30 mV

15. ~74 pe

16. LabView based
DAS

18. No PMT
Glass
Cherenkov
signal

19. With PMT
Glass
Cherenkov
signal

21. No PMT
Glass
Cherenkov
signal

22. With PMT
Glass
Cherenkov
signal

24. 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

26. <E> = 0.12 VEM x 240 MeV/VEM = 29 MeV for knock-on electrons

27. Shaded hist. shows
electrons selected
for Q/A < .5
risetime < .5
With E~ 10.8 MeV

28. Muon Decay in a WC Detector
Raw Data
With cut C2 > C1
t = ms

29. <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).

30. Composition of showers with known m/EM and use of neural networks

31. Nm/Ne
Strongly
Correlated
With Primary
Mass, i.e.
~2 x for
Fe wrt p

32. 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

33. Stopping muon or electron Q~0.12 VEM (9 pe) T12~3ns Isolated Muon
Shower Q>7 VEM
(500 pe)
T12>15ns

34. 4 muons, 15ns Data trace Q=7.8 VEM 8 muons 15 ns 33 “electrons” 25 ns

35. Parameters for Data and Composed Events
Charge (VEM)
Amplitude (V)
T10-50
(ns)
T10-90

36. 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)

37. Training and Clasification Results for Two Classes
8 m 4m
33 e
Data
65%
39%
68%
35%
61%
32%
Class

38. Training and Clasification Results for Two Classes
8 m 0m
66 e
Data
65%
33%
78%
35%
67%
22%
Class

39. 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

40. 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.

41. 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

50. 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.

51. 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.

52. 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 eV.
Area: 4000 m^2
10 Liquid Ssintillator Detectors (Bicron BC-517H)
4 Water Cherenkov Detectors
PMT EMI 9030 A

53. 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

54. EAS-UAP
Control Room
Home-made DAQ electronics under construction

55. 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

56. DAQ System
Calibration
Rate: 250 events/m2/s

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

58. Monitoring and Calibration

59. Calibration

60. Calibration

61. MC Simulations using Aires
Algorithm for
Locating the
Shower Core

62. 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

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

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

65. 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

66. 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

67. Mass Composition Hybrid Array
Solution:

68. Iterations
Start with
Ne=82,300
Nmu = 32700
E0 = 233 TeV
Iterations
End with
Ne=68000
Nmu = 18200
E0 = 196 TeV

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

70. 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:

71. 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: