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Yakutsk array

Study of the Energy Spectrum and the Composition of the Primary Cosmic Radiation at Super-high Energies. By L.G. Dedenko 1 , A.V. Glushkov 2 , G.F. Fedorova 1 , S.P. Knurenko 2 , a.A. Makarov 2 , M.I. Pravdin 2 , T.M. Roganova 1 , I.Ye. Sleptzov 2

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Yakutsk array

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  1. Study of the Energy Spectrum and the Composition of the Primary Cosmic Radiation at Super-high Energies QUARKS-2010, Kolomna

  2. By L.G. Dedenko1, A.V. Glushkov2, G.F. Fedorova1, S.P. Knurenko2, a.A. Makarov2, M.I. Pravdin2, T.M. Roganova1, I.Ye. Sleptzov2 • 1. M.V. Lomonosov Moscow State University, Faculty of Physics and D.V. Skobeltzin Institute of Nuclear Physics, Moscow, 119992, Leninskie Gory, Russian Federation • 2. Insitute of cosmic rays and aeronomy. Yakutsk, Russian Federation QUARKS-2010, Kolomna

  3. Yakutsk array • The Yakutsk array includes • the surface scintillation detectors (SD) and • detectors of theVavilov-Cherenkovradiation • and undergrounddetectors of muons (UD) with the threshold energy ~1 GeV. QUARKS-2010, Kolomna

  4. Detectors readings induced by EAS particles • The various particles • of Extensive Air Showers (EAS) • at the observation level • hit detectors and • induce some signals sampled as • detector readings QUARKS-2010, Kolomna

  5. Standard approach of energy estimation • s(600) – signal at 600 m in the vertical EAS used to estimate energy E of EAS. • 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=4.6·1017· s(600), eV QUARKS-2010, Kolomna

  6. 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 • energy E: • E=3·1017·s(600), eV QUARKS-2010, Kolomna

  7. Spectrum • Energy spectra are different for these approaches QUARKS-2010, Kolomna

  8. points ─ Yakutsk data circles ─ Yakutsk (calculation like AGASA) stars ─ PAO QUARKS-2010, Kolomna

  9. The CIC method • The constant intensity cut (CIC) method: • systematic error! • For Yakutsk array the absorption length • 458 g/cm2 • (to be compared with 340 g/cm2) QUARKS-2010, Kolomna

  10. Yakutsk array. New approach • All detectors readings • are suggested to be used to study • the energy spectrum and • the chemical composition of • the primary cosmic radiation • at ultra-high energies • in terms of some model of hadron interactions. QUARKS-2010, Kolomna

  11. The new method • For the individual EAS • the energy E and • the type of the primary particle, (atomic number A), which induced EAS, • parameters of model of hadron interactions, • peculiar development of EAS in the atmosphere • are not known QUARKS-2010, Kolomna

  12. The new method • The goal: • to find estimates of • the energy E and atomic number A, • parameters of model of hadron interactions, • peculiar development of EAS in the atmosphere • for each individual shower QUARKS-2010, Kolomna

  13. The new method It has been suggested for the one observed EAS to estimate all detector readings • for manysimulated individual showers, • induced by various primary particles • with different energies • in terms of various models. QUARKS-2010, Kolomna

  14. The new method • All these detector readings • for all simulated individual showers • should be compared with • detector readings of • one observed EAS QUARKS-2010, Kolomna

  15. The new method • The best estimates of • the energy E, • the atomic number A and • parameters of model and • peculiar development of EAS in • the atmosphere are searched by • the χ2 method. QUARKS-2010, Kolomna

  16. The new method • The best estimates • of the arrival direction and • core location • are also searched by the χ2 method. QUARKS-2010, Kolomna

  17. Simulations • Simulations of the individual shower developmentin the atmosphere • have been carried out with the help of • the codeCORSIKA-6.616 [8] • in terms of the models QGSJET2 [9] and Gheisha 2002 [10] • with the weightparameter ε=10-8(thinning). QUARKS-2010, Kolomna

  18. Simulations • The program GEANT4 [11] has been used • to estimate signals in the scintillation detectors • from electrons, positrons, gammas and muons • in each individual shower. QUARKS-2010, Kolomna

  19. Detector model QUARKS-2010, Kolomna

  20. Signals in scintillation detector • Signals ∆E in MeV • as functions of • energy E • and the cos( teta) • (teta – the zenith angle) • of incoming particles QUARKS-2010, Kolomna

  21. Electrons QUARKS-2010, Kolomna

  22. Positrons QUARKS-2010, Kolomna

  23. Gammas QUARKS-2010, Kolomna

  24. Отклики от мюонов Muons QUARKS-2010, Kolomna

  25. Minimum of the function χ2 • Readings of all scintillation detectors have been used to search for the minimum of the function χ2in the square with the width of 400 m and a • center determined by data with a step of 1 m. • These readings have been compared with calculated responses for E0=1020 eV multiplied by the coefficient C. This coefficient changed from 0.1 up to 4.5 with a step of 0.1. QUARKS-2010, Kolomna

  26. Minimum of the function χ2 • Thus, it was assumed, that the energy of a shower and signals in the scintillation detectors are proportional to each other in some small interval. • New estimates of energy • E =C·E0 eV, QUARKS-2010, Kolomna

  27. Results of energy estimations • The 16 various values of energy estimates for 16 individual simulated showers induced by • protons, He, O and Fe nuclei • have been obtained for the same sample of the 31 experimental readings of the observed giant shower with different values of the function χ2. QUARKS-2010, Kolomna

  28. Results for the most energetic shower observed at the Yakutsk array QUARKS-2010, Kolomna

  29. QUARKS-2010, Kolomna

  30. Simulations • New estimates of energy • of the giant air showerobserved at YA • have been calculated in terms of the QGSJET2 and Gheisha 2002 models: • E≈2.·1020eV forthe proton primaries and • E≈1.7·1020eV for the primary iron nuclei. QUARKS-2010, Kolomna

  31. Minimum of the function χ2 • Coordinates of axis and • values of the function χ2 • have been obtained • for each individual shower QUARKS-2010, Kolomna

  32. Results of energy estimations • The energy estimates are minimal for the iron nuclei primaries • and change inside the interval (1.6−1.75)· 1020 eV • with the value of the χ2 ~ 1.1 per one degree of freedom. QUARKS-2010, Kolomna

  33. Results of energy estimations • For the proton and helium nuclei primaries energy estimates are maximal and • change inside the interval (1.8−2.4)·1020 eV • with the value of the χ2 ~ 0.9 per one degree of freedom. QUARKS-2010, Kolomna

  34. Results of energy estimations • For the oxygen nuclei primaries the energy estimates are • in the interval (1.8−2)·1020eV • which isbetween intervals for proton and iron nuclei primaries • with the value of the χ2 ~ 0.95 per one degree of freedom. QUARKS-2010, Kolomna

  35. Results of energy estimations • Dependence of the value χ2 • per one degree of freedom • on the coefficient • C=E/(1020 eV) QUARKS-2010, Kolomna

  36. QUARKS-2010, Kolomna

  37. QUARKS-2010, Kolomna

  38. QUARKS-2010, Kolomna

  39. QUARKS-2010, Kolomna

  40. Reality of the Yakutsk DATA • The sampling time of signal in the scintillation detetor • τ=2000 ns QUARKS-2010, Kolomna

  41. Fraction of signal: 1-100 m, 2- 600 m, 3- 1000 m, 4-1500 m QUARKS-2010, Kolomna

  42. Energy spectrum • The base spectrum • Jb(E)= A·(E)-3.25, • and the reference spectrum • Jr(E) • areintroduced on the base of the HiRes data QUARKS-2010, Kolomna

  43. Energy spectrum • New variable • y=lgE • In four energy intervals yi(i=1, 2, 3 and 4) • 17.<y1<18.65, • 18.65<y2<19.75, • 19.75<y3<20.01 and • y4>20.01 QUARKS-2010, Kolomna

  44. Spectrum Jr(E) has been approximated by the following exponent functions • J1(E)=A·(E)-3.25, • J2(E)=C·(E)-2.81, • J3(E)=D·(E)-5.1, • J4(E)=J1(E)=A·(E)-3.25 • Constants C and D may be expressed through A and equations forJr(E) at the boundary points. QUARKS-2010, Kolomna

  45. Spectrum • we assume the reference spectrum as • lgzi=lg(Ji(E)/J1(E)), • where i=1, 2, 3, 4. QUARKS-2010, Kolomna

  46. Spectrum • This reference spectrum is represented as follows • lgz1=0, • lgz2=0.44·(y -18.65), • lgz3=0.484-1.85·(y -19.75) • lgz4=0 QUARKS-2010, Kolomna

  47. Spectrum • Results of the spectra J(E) • observed at various arrays have been expressed as • lg z=lg (J(E)/Jb(E)) • and are shown in comparison with the reference spectrum. QUARKS-2010, Kolomna

  48. Spectrum • Datalgz=lg(J(E)/Jb(E)) observed at various arrays areshown in Fig. as follows: • (a) − HiRes2(open circles), HiRes1(solid squares), • (b) − PAO (solid circles), • (c) − AGASA (solid triangles), • (d) − Yakutsk (solid pentagons). • The reference spectrum is also shown on all Figures (solid line). QUARKS-2010, Kolomna

  49. HiRes QUARKS-2010, Kolomna

  50. PAO QUARKS-2010, Kolomna

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