Ground Detectors for the Study of Cosmic Ray Showers

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 anduse 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-2min-1

9. t1= t =2.208 +- 0.027 ms t2=1.979 +- 0.039 ms Gc = t2-1 - t1-1= 0.050.01 ms-1 m+/m - =1.28 +-0.06

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. 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. 0.12 VEM <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 = 2.08 +- .12ms

29. Stopping muon at 0.95 VEM Decay electron at 0.17 VEM <E> = 41 +- 11 MeV for decay electrons 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 anduse of neural networks

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

32. 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 Q~1 VEM (74 pe) T12~12 ns Shower Q>7 VEM (500 pe) T12>15ns

34. Data trace Q=7.8 VEM 8 muons 15 ns 4 muons, 15ns 33 “electrons” 25 ns 66 “electrons” 25 ns

35. Parameters for Data and Composed Events

36. 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 Class

38. Training and Clasification Results for Two Classes Class

39. Training and Clasification Results for Three Classes 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 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.