By L.G. Dedenko 1 , A.V. Glushkov 2 ,

The 23-European Symposium and the 32 Russian cosmic ray conference 3-7 July Moscow

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Possible composition of the primary particles at ultrahigh energies

observed at the Yakutsk array


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• By

• L.G. Dedenko1, A.V. Glushkov2,

• G.F. Fedorova1, S.P. Knurenko2, A.K. Makarov2, L.T. Makarov2, M.I. Pravdin2, T.M. Roganova1, A.A. Saburov2 , I.Ye. Sleptzov2

• 1. M.V. Lomonosov Moscow State University, Faculty of Physics and D.V. Skobeltsin Institute of Nuclear Physics, Moscow, 119992,

• Leninskie Gory, Russian Federation

• 2. Insitute of cosmic rays and aeronomy. Yakutsk, Russian Federation


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Motivation

• Testing the overall CR spectrum formation scenarios


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The “dip” scenario of the overall CR spectrum formation

• In the model of uniformly distributed extragalactic sources with a power law spectrum of generation, the proton flux must first decrease (a dip), then increase (a bump) and drop steeply (the GZK effect) [3, 4].

• [3] Berezinsky V S and Grigorieva S I 1988 Astron. Astrophys. 199 1

• [4] Berezinsky V S, Gazizov A Z, Grigorieva S I 2006 Phys. Rev. D 74 043005


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The “ankle” scenario

• In the alternative “ankle” scenario [6] the extragalactic component dominates at energies above 1019 eV. The CR composition in this scenario is considerably

• heavier at energies 1018 − 1019 eV

• [6] Wibig T and Wolfendale W 2005 J. Phys. G: Nucl. Part. Phys. 31 255


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The scenario by Berezhko E G • The peak of rather heavy composition is predicted at

energies ~ 1017 eV followed by • a sharp decrease of atomic number A within of the

energy interval 1017 − 1018 eV. It is regarded as a signature of the transition from galactic to extragalactic CR.

• The second peak of heavy elements in the atomic number distribution is predicted at energy ~ 1019 eV. So a profound increase of heavy composition should be observed within the energy interval 1018 − 1019 eV [5].

• [5] Berezhko E G 2009 Astrophys. J. 698 L138


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Study of composition

• Standard approach:

• The depth Xmax

• of shower maximum

• vs. E


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Before LHC


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After LHC


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23-d European cosmic ray symposium• Conclusion by T. Pierog, KIT, Karlsruhe,

Germany (03.07.2012)

• …light composition

• is excluded • at high energies…


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Question by Angela Olinte• The UHECR in CERN

• Febrary 2012

•do we have pure protons anywhere???


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We believe the answer is

• Yes


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Alternative approach• THE FRACTION OF MUONS α

• at 600 m from the shower core:

α=sμ(600)/s(600) sμ(600) – a signal in the

underground detector s(600) – a signal in the surface detector


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Yakutsk array• The Yakutsk array includes

• the surface scintillation detectors (SD), detectors of the Vavilov-Cherenkov radiation,

• underground detectors of muons (UD)

• with suggested the threshold energy

• ~1 GeV. • It was shown that the less energetic

muons may hit the underground detectors.


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Simulations• Simulations of the individual shower

development in the atmosphere

• have been carried out with the help of

• the code CORSIKA-6.616 • [7] Heck D, Knapp J, Capdevielle J-N et al.

1998 CORSIKA: A Monte Carlo Code to Simulate Extensive Air Showers

• Report FZKA 6019 Forschungszentrum Karlsruhe


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Simulations• Simulations

• in terms of the models QGSJET2 • [8] Ostapchenko S S 2006 Nucl. Phys. Rev. B (Proc.

Suppl.) 151 143

• and Gheisha 2002 • [9] Fesefeldt H C 1985 GHEISHA program Technical

report PITHA 85-02, III Physikalisches Institut, RWTH Aachen. Physikzentrum

• with the weight parameter ε=10-8 (thinning).


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Simulations• The program GEANT4 • [10] The GEANT4 Collab. Available from

http://geant4.web.cern.ch/geant4/support/gettingstarted.shtml

• has been used • to estimate signals • in the scintillation detectors • from electrons, positrons, gammas and

muons • in each individual shower.


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Study of the chemical composition

• Muon density with energies above 1 GeV

• for the primary protons with the energy E:

• ρμ(600, >1 GeV)=a·Eb

• Decay processes are decreasing for higher energies E.

• b<1


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Study of the chemical composition

• Muon density for the primary nuclei

• with atomic number A

• ρμ(600)=a·Ac·Eb

• c>0 (c=1-b)• QGSJET2: b=0.895, c=0.105

• For Fe:

• A0.105=1.53


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Study of the chemical composition• The signals are calibrated• in the surface detectors

• s(600)=∆Es(600)/δEs(600)• and in the underground detectors

• sμ(600)=∆Eu(600)/δEu(600)• ∆Es(600) and ∆Eu(600) • from the EAS particles• δEs(600) and δEu(600) • from the one vertical muon


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Standard approach of energy estimation at the Yakutsk array

• s(600) – the signal at 600 m

• in the vertical EAS measured in

• VEM’s

• (VERTICAL EQUIVALENT MUON)• is used to estimate the energy E

of EAS.


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Standard approach of energy estimation at the Yakutsk array

• DATA:

• 1. The CIC method to estimate s(600) from data for the inclined EAS.

• 2. The signal s(600) is calibrated with

• help of the Vavilov-Cherenkov radiation

• E=(4.6+-1.2)·1017· s(600)0.98, eV


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Standard AGASA approach

• Like AGASA:

• 1. The CIC method to estimate s(600) from data for the inclined EAS.

• 2. Calculation s(600) for EAS with

• the energy E:

• E=(3+-0.2)∙1017·s(600), eV


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Spectrum• Data:• s(600)= E/((4.6+-1.2)·1017) • Simulation:• s(600)= E/((3.+-0.2)∙1017) • The simulated signal larger!• The fraction α is less!


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Spectrum• Data:• s(600)= E/((4.6+-1.2)·1017) • Simulation:• s(600)= E/((3.+-0.2)∙1017) • The simulated signal larger!• The energy spectra are different• for these approaches.


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Question

• Is it possible

• to increase the signal s(600) more,

• to be able

• to decrease the fraction α?


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points ─ Yakutsk data circles ─ Yakutsk (calculation like AGASA)

stars ─ PAO


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Answer• In the formula

• E=a·1017·s(600)• The coefficient a should be less than 4.6 and

higher than 3 (difference by a factor 1.53).

• The magnitude a=3 leads to

• the maximal signal s(600) and

• the minimal value of the muon fraction.


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Results

• Results of calculations


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The fraction α of muons in EAS calculated in terms of the QGSJET-II and Gheisha-2002d models for the primary protons (solid line) and the primary iron nuclei (dashed line) and observed at the YaA [11] (dots with error bars) versus the energy E.


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Question

•Where are protons?


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Another question

Are the models used reliable?


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At energies above 100 GeV

•QGSJET2?• Kochanov A A, Sinegovskaya T S, Sinegovsky

S I 2008 Astrop. Physics 30 219

Panov A D, Adams J H Jr, Ahn H S et al. 2007 Bull. Russ. Acad. Sci. Phys. 71 494


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The energy spectrum of vertical muons


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Ratio R1 of the observed intensities

(Δ − [21], - [22],● − [23],■ − [24],○ − [25],+ − [26])

of the vertical muons to the calculated muon intensityin terms of the QGSJET-II model vs. an impulse p of muons (A.Kochanov).


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Conclusion• Difference is increasing with the

energy E • from 1.5 to 3 • at E=107 GeV.• We adopted the minimal value 1.5• (A. Kochanov)


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Below 100 GeV

•GHEISHA?• Maris I C, Engel R, Arrido X et al. 2009 arXiv:

0907.0409v1 [astro-ph.CO]


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Ratio R2 of muon densities calculated in terms of the FLUCA model to the intensty calculated with the Gheisha-2002d model vs. a distance r from a shower axis (R. Engel).


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Conclusion• GHEISHA• gives the density of muons at 600 m

• from the shower core• by a factor f3=1.1 less than

the FLUKA• (R. Engel)


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Corrected results


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The fraction α of muons corrected due to results of [19, 21-26, 27, 29].


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Answer

•We hope

•that protons are observed


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The dependence of the atomic number A on α

• lnA= ln(α / αp ) / 0.105

• Here α is a measured value

• and

• αp is calculated for protons.


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Dependence of the atomic number <ln A> on the energy E for YaA


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CONCLUSION

• We hope

• that protons are observed in the energy interval

• 3·1018 – 1019 eV• The new scenarios of the cosmic ray spectrum

formation should be developed


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Conclusions are model dependent• The Coulomb scattering of charged

particle (electrons, positrons)

• and the pt distribution of hadrons

• (for muon scattering) should be taken into account precisely in calculations

• of the lateral spread of these particles.


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Acknowledgements.• Moscow authors thank G.T. Zatsepin LSS

(grant 871.2012.2 ) for support.

• Authors from Yakutsk thank RFBR grant 11-02-12193 ofim and by the state contract 16.518.11.7075 from the Department of science and education of Russian Federation.

• for support.


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• Thank you for attention


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Dependence of the atomic number <ln A> on the energy E for various experiments: ● − [12], ■ − [9], □ − [33], ▲− [32].

By L.G. Dedenko 1 , A.V. Glushkov 2 ,

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