1. Application for Pierre Auger Observatory.
On the possibility to discriminate the mass of the primary cosmic ray using the muon arrival times from extensive air showers:
Application for Pierre Auger Observatory.
N. Arsene1,2, H. Rebel 3, O. Sima 2
1ISS Bucharest, Romania, 2University of Bucharest, Romania, 3KIT, Karlsruhe, Germany

2. Content : Cosmic rays energy spectrum Extensive air showers (EAS)
EAS experimental techniques at the Pierre Auger Observatory (PAO)
Methods to determine mass of primary cosmic ray
On the possibility to discriminate the mass of the primary cosmic ray using the muon arrival times
Results and outlook

3. 1. Cosmic rays energy spectrum
Greisen–Zatsepin–Kuzmin cutoff
(GZK cutoff)
5 x 1019 eV

4. 2. Extensive air showers (EAS)

5. 2. Extensive air showers (EAS)
( Xmaxp - XmaxFe ) ≈ 100 g cm-2
Gaisser–Hillas :
Nishimura–Kamata–Greisen (NKG) approximation :
Nch = the total number of charged particles
s = “age” parameter
r0 = Moliere radius ~ 79 m
C = constant

6. 2. Extensive air showers (EAS)
Heck D. et al.[3] Longitudinal EAS development. MC simulations with CORSIKA

7. 3. EAS experimental techniques at the Pierre Auger Observatory (PAO)
Southern Hemisphere, Argentina
Surface km2
1600 surface detectors water Cherenkov (SD)
4 stations fluorescence detectors
A. Creusot [4]

8. 3. EAS experimental techniques at the Pierre Auger Observatory (PAO)
Water Cherenkov tanks
AUGER COLABORATION [5]
altitude m
diameter 3.6 m
height m
detects : muons, electrons,
positrons, photons

9. 3. EAS experimental techniques at the Pierre Auger Observatory (PAO)
Surface detectors reconstruction
AUGER COLABORATION [5] , Eveniment recorded by Pierre Auger Observatory , E = 5 x 1018 eV
Primary energy :

10. 3. EAS experimental techniques at the Pierre Auger Observatory (PAO)
Fluorescence detectors (FD)
Jos Bellido, for the ́ Pierre Auger Collaboration [6]
3.5 m x 3.5 m spherical mirror -> 440 PMT camera
Field of view 300 azimuth x elevation
1 pixel -> 1.50

11. 3. EAS experimental techniques at the Pierre Auger Observatory (PAO)
Fluorescence detectors (FD) reconstraction
Shower Detector Plane reconstruction :
nSDP errors ̴ tenths of a degree
Shower Axis reconstruction :
AUGER COLABORATION [5]
Shower axis errors ̴ 1 degree

12. 3. EAS experimental techniques at the Pierre Auger Observatory (PAO)
Fluorescence detectors (FD) reconstraction
AUGER COLABORATION [5] Eveniment recorded by PAO, zenith angle = 56º , distance core - FD detector = 13 km

13. 4. Methods to determine mass of primary cosmic ray
Dependence of Xmax :
M. Risse [8] Longitudinal showers profile . MC simulations, E=10^19 eV, vertical

14. 4. Methods to determine mass of primary cosmic ray
Correlation between Xmax and Nµ (Patrick Younk and Markus Risse, 2009) :
Patrick Younka, Markus Rissea [9] Xmax - Nµ distribution , E = eV, zenith = 45 ͦ. Average per 1000 simulations
using Conex code with QGSJET-01 model
Ideal detectors
Real detectors : σ Nµ = 20 %
σ Xmax = 20 g cm-2

15. 4. Methods to determine mass of primary cosmic ray
Time asymmetry in the shower development
Hernan Wahlberg, for the Pierre Auger Collaboration [10]
Position of maximum asymmetry vs.
primary energy for different models and primaries.
Hernan Wahlberg, for the Pierre Auger Collaboration [10]
Asymmetry development for the different samples
t ½ = mean risetime
r = radius
ζ = azimuth angle
Θ = zenith angle

16. 5. On the possibility to discriminate the mass of the primary cosmic ray using the muon arrival times
Proposed by H. Rebel et al. for KASCADE colaboration, [12]

17. 6. Results and outlook
Azimuthal distributions of muons in observable plane.p, E=8x10^17eV, zenith=30,S->N, CORSIKA - QGSJET01 model

18. 6. Results and outlook
Momentum distribution of muons at ground , CORSIKA simulations – QGSJET01 model

19. 6. Results and outlook
Distribution of arrival times of muons at ground , CORSIKA simulations – QGSJET01 model

20. 6. Results and outlook
Distribution of the reconstructed atmospheric depth of muon production , CORSIKA simulations – QGSJET model

21. 10 simulations (left) and 100 simulations (right)
6. Results and outlook
Distribution of the reconstructed atmospheric depth of muon production using infill array detectors, average over
10 simulations (left) and 100 simulations (right)
30 +/- 3 muons in infill detectors Fe, E=8x10^17 eV
20 +/- 2 muons in infill detectors p, E=8x10^17 eV
Xmax mup ≈ 400 g cm-2
Xmax muFe ≈ 250 g cm-2

22. 6. Outlook
Average number of muons per square meter as a function of radial distance to the core of the shower. Averaged over 100 showers with one sigma as error bars. Zero inclination. [11]
- Analisys of a large set of CORSIKA simulations with primary energy above 10^18 eV
- Find maximum distribution of the reconstructed atmospheric depth of muons production
Possibility to implement this method as a complementary method for determine the primary cosmic ray mass
in Pierre Auger Experiment

23. Bibliography :
[1] Engel R. et. Al. 2011, Annu Rev. Nucl. Part. Sci. 61:467-89
[2] Diego Garca Gamez, 2010, Dpto. de Fsica Teorica y del Cosmos & CAFPE
Universidad de Granada
[3] Heck D et al 1998 FZKA Report Forschungszentrum Karlsruhe 6019
[4] A. Creusot, 2010, Latest results of the Pierre Auger Observatory, Nuclear Instruments
and Methods in Physics Research A 662 (2012) S106–S112
[5] AUGER COLABORATION, Properties and performance of the prototype
instrument for the Pierre Auger Observatory, Nuclear Instruments and Methods in
Physics Research A 523 (2004) 50–95
[6] Jos Bellido, for the ́ Pierre Auger Collaboration, Mass Composition Studies of the Highest Energy
Cosmic Rays, arXiv: v1 [astro-ph.HE].
[7] M. Unger, et al [Pierre Auger Collaboration], Proc. 30th ICRC, , Merida, (2007),
arXiv: v1 [astro-ph].
[8] M. Risse, Acta Phys.Polon. B35 ,1787, (2004), arXiv:astro-ph/ v1.
[9] Patrick Younka, Markus Rissea, Sensitivity of the correlation between the depth of shower
maximum and the muon shower size to the cosmic ray composition, /j.astropartphys
[10] Hernan Wahlberg, for the Pierre Auger Collaboration, Mass composition studies using the
surface detector of the Pierre Auger Observatory , Nuclear Physics B (Proc. Suppl.) 196 (2009) 195–198 .
[11] Jochem D. Haverhoek, 2006 , Ultra High Energy Cosmic Ray Extensive Air Shower simulations using CORSIKA
[12] I.M.Brancus ,H.Rebel, A.F.Badea et. al. J.Phys.G29: ,2003 Features of Muon Arrival Time
Distributions of High Energy EAS at Large Distances From the Shower Axis

24. M. Unger, et al [7] Auger results for the Mean Xmax
measurements as a function of energy