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