N. Arsene1,2, H. Rebel 3, O. Sima 2

1ISS Bucharest, Romania, 2University of Bucharest, Romania, 3KIT, Karlsruhe, Germany

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.

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Content :

1.Cosmic rays energy spectrum

2.Extensive air showers (EAS)

3.EAS experimental techniques at the Pierre Auger Observatory (PAO)

4.Methods to determine mass of primary cosmic ray

5.On the possibility to discriminate the mass of the primary cosmic ray using the muon arrival times

6.Results and outlook

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1. Cosmic rays energy spectrum

eV10 above toGeV 1 from extends

rays cosmicprimary of spectrumenergy The20

γEJ(E)

centurykm / particle 1 tosm / particle 1 J(E) 22

eV 10 x 6 ankle""

eV 1010 knee""19

1615

Greisen–Zatsepin–Kuzmin cutoff (GZK cutoff) 5 x 1019 eV

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2. Extensive air showers (EAS)

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2. Extensive air showers (EAS)

Gaisser–Hillas :

2g/cm 70λ

massprimary and E ~ )X(X 00max

0max lnE ~ )X(X

lnA~X /A E~X

nucleons)(A primary nucleus

max0max

( Xmaxp - Xmax

Fe ) ≈ 100 g cm-2

Nishimura–Kamata–Greisen (NKG) approximation : Nch = the total number of charged particles s = “age” parameter r0 = Moliere radius ~ 79 m C = constant

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2. Extensive air showers (EAS)

Heck D. et al.[3] Longitudinal EAS development. MC simulations with CORSIKA 6

3. EAS experimental techniques at the Pierre Auger Observatory (PAO)

eV10 exceeding eV10energyPrimary 2118

Southern Hemisphere, Argentina

Surface 3000 km2

1600 surface detectors water Cherenkov (SD)

4 stations fluorescence detectors

A. Creusot [4]

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3. EAS experimental techniques at the Pierre Auger Observatory (PAO)

Water Cherenkov tanks

AUGER COLABORATION [5]

altitude 1500 mdiameter 3.6 mheight 1.55 m

detects : muons, electrons, positrons, photons

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3. EAS experimental techniques at the Pierre Auger Observatory (PAO)

AUGER COLABORATION [5] , Eveniment recorded by Pierre Auger Observatory , E = 5 x 1018 eV

Surface detectors reconstruction

1.052 S(1000)] 1)-)11.8(sec(1[ 0.12E(EeV) Primary energy :

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3. EAS experimental techniques at the Pierre Auger Observatory (PAO)

Fluorescence detectors (FD)

3.5 m x 3.5 m spherical mirror -> 440 PMT cameraField of view 300 azimuth x 28.60 elevation1 pixel -> 1.50

Jos Bellido, for the B Pierre Auger Collaboration [6]

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3. EAS experimental techniques at the Pierre Auger Observatory (PAO)

Fluorescence detectors (FD) reconstraction

AUGER COLABORATION [5]

SDP vector n

sky in thedirection r

i"" pixelin signal w

minimum)r(n wχ

SDP

i

i

2iSDP

ii

2

nSDP errors ̴� tenths of a degree

Shower Detector Plane reconstruction :

Shower Axis reconstruction :)/2]- tan[(/cRtt i0p0expi,

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Shower axis errors ̴� 1 degree

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 km12

4. Methods to determine mass of primary cosmic ray

M. Risse [8] Longitudinal showers profile . MC simulations, E=10^19 eV, vertical

Dependence of Xmax :

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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 = 1019 eV, zenith = 45 M. Average per 1000 simulations using Conex code with QGSJET-01 model

a) Ideal detectorsb) Real detectors : σ Nµ = 20 % σ Xmax = 20 g cm-2

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Time asymmetry in the shower development

4. Methods to determine mass of primary cosmic ray

Hernan Wahlberg, for the Pierre Auger Collaboration [10]Position of maximum asymmetry vs.primary energy for different models and primaries.

t ½ = mean risetimer = radius ζ = azimuth angle Θ = zenith angle

Hernan Wahlberg, for the Pierre Auger Collaboration [10]Asymmetry development for the different samples

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5. On the possibility to discriminate the mass of the primary cosmic ray using the muon arrival times

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Proposed by H. Rebel et al. for KASCADE colaboration, 2003 [12]

6. Results and outlook

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

6. Results and outlook

Momentum distribution of muons at ground , CORSIKA simulations – QGSJET01 model

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6. Results and outlook

Distribution of arrival times of muons at ground , CORSIKA simulations – QGSJET01 model

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6. Results and outlook

Distribution of the reconstructed atmospheric depth of muon production , CORSIKA simulations – QGSJET model

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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 eV20 +/- 2 muons in infill detectors p, E=8x10^17 eV

Xmax mup ≈ 400 g cm-2

Xmax muFe ≈ 250 g cm-2

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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

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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:0901.3389v1 [astro-ph.HE].[7] M. Unger, et al [Pierre Auger Collaboration], Proc. 30th ICRC, , Merida, (2007), arXiv:0706.1495v1 [astro-ph].[8] M. Risse, Acta Phys.Polon. B35 ,1787, (2004), arXiv:astro-ph/0402300v1.[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, 10.1016/j.astropartphys.2012.03.001.[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.G29:453-474,2003 Features of Muon Arrival Time Distributions of High Energy EAS at Large Distances From the Shower Axis

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