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Composition of Primary Particles at Ultrahigh Energies Observed at the Yakutsk Array

Explore the composition of primary particles at ultrahigh energies, testing different cosmic ray spectrum formation scenarios, including the "dip," "ankle," and Berezhko scenario. Study focuses on shower maximum depth, compositions, and muon fractions using simulations and data from the Yakutsk array.

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Composition of Primary Particles at Ultrahigh Energies Observed at the Yakutsk Array

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  1. Possible composition of the primary particlesat ultrahigh energiesobserved at the Yakutsk array The 23-European Symposium and the 32 Russian cosmic ray conference 3-7 July Moscow

  2. 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

  3. Motivation • Testing the overall CR spectrum formation scenarios The 23-European Symposium and the 32 Russian cosmic ray conference 3-7 July Moscow

  4. 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

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

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

  7. Study of composition • Standard approach: • The depth Xmax • of shower maximum • vs. E The 23-European Symposium and the 32 Russian cosmic ray conference 3-7 July Moscow

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

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

  10. 23-d European cosmic ray symposium • Conclusion by T. Pierog, KIT, Karlsruhe, Germany (03.07.2012) • …light composition • is excluded • at high energies… The 23-European Symposium and the 32 Russian cosmic ray conference 3-7 July Moscow

  11. Question byAngela Olinte • The UHECR in CERN • Febrary 2012 • do we have pure protons anywhere??? The 23-European Symposium and the 32 Russian cosmic ray conference 3-7 July Moscow

  12. We believe the answer is • Yes The 23-European Symposium and the 32 Russian cosmic ray conference 3-7 July Moscow

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

  14. Yakutsk array • The Yakutsk array includes • the surface scintillation detectors (SD),detectors of theVavilov-Cherenkovradiation, • 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

  15. Simulations • Simulations of the individual shower developmentin the atmosphere • have been carried out with the help of • the codeCORSIKA-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

  16. 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 weightparameter ε=10-8(thinning). The 23-European Symposium and the 32 Russian cosmic ray conference 3-7 July Moscow

  17. 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

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

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

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

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

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

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

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

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

  26. Question • Is it possible • to increase the signal s(600) more, • to be able • to decrease the fraction α? The 23-European Symposium and the 32 Russian cosmic ray conference 3-7 July Moscow

  27. points ─ Yakutsk data circles ─ Yakutsk (calculation like AGASA) stars ─ PAO The 23-European Symposium and the 32 Russian cosmic ray conference 3-7 July Moscow

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

  29. Results • Results of calculations The 23-European Symposium and the 32 Russian cosmic ray conference 3-7 July Moscow

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

  31. Question • Where are protons? The 23-European Symposium and the 32 Russian cosmic ray conference 3-7 July Moscow

  32. Another question Are the models used reliable? The 23-European Symposium and the 32 Russian cosmic ray conference 3-7 July Moscow

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

  34. The energy spectrum of vertical muons The 23-European Symposium and the 32 Russian cosmic ray conference 3-7 July Moscow

  35. Ratio R1 oftheobservedintensities (Δ − [21], - [22], ● − [23], ■ − [24], ○ − [25], + − [26]) of the vertical muons to the calculated muon intensity in terms of the QGSJET-II model vs. an impulse p of muons (A.Kochanov). The 23-European Symposium and the 32 Russian cosmic ray conference 3-7 July Moscow

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

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

  38. Below 100 GeV • GHEISHA? • Maris I C, Engel R, Arrido X et al. 2009 arXiv: 0907.0409v1 [astro-ph.CO] The 23-European Symposium and the 32 Russian cosmic ray conference 3-7 July Moscow

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

  40. Conclusion • GHEISHA • gives the density of muons at 600 m • from the shower core • by a factor f3=1.1 lessthan the FLUKA • (R. Engel) The 23-European Symposium and the 32 Russian cosmic ray conference 3-7 July Moscow

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

  42. The fraction α of muons corrected due to results of [19, 21-26, 27, 29]. The 23-European Symposium and the 32 Russian cosmic ray conference 3-7 July Moscow

  43. Answer • We hope • that protons are observed The 23-European Symposium and the 32 Russian cosmic ray conference 3-7 July Moscow

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

  45. Dependence of the atomic number <ln A> on the energy E for YaA The 23-European Symposium and the 32 Russian cosmic ray conference 3-7 July Moscow

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

  47. Conclusions are model dependent • The Coulomb scattering of charged particle (electrons, positrons) • and the pt distribution of hadrons • (for muonscattering) should be taken into account precisely in calculations • of the lateral spread of these particles. The 23-European Symposium and the 32 Russian cosmic ray conference 3-7 July Moscow

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

  49. Thank you for attention The 23-European Symposium and the 32 Russian cosmic ray conference 3-7 July Moscow

  50. Dependence of the atomic number <ln A> on the energy E for various experiments: ● − [12], ■ − [9], □ − [33], ▲− [32]. The 23-European Symposium and the 32 Russian cosmic ray conference 3-7 July Moscow

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