Part 1: Cosmic Rays Spectrum in the Energy Range 1015 – 1018 eV and its Interpretation

Part 1: Cosmic Rays Spectrum in the Energy Range 1015 – 1018 eV and its Interpretation

• Part 1: Cosmic Rays Spectrum in the Energy Range 1015 – 1018 eV and its Interpretation

• History of Yakutsk array

• Yakutsk array

• Cosmic ray spectrum

• Spectrum interpretation

• Part 2: Mass Composition of Cosmic Rays at Ultra High Energies

• Methods for estimating mass composition

• Mass composition of Cosmic rays data interpretation (recent results)

Second phase (1974 – 1994):

• Second phase (1974 – 1994):

• The area was increased to 18 km2 with 43 stations with scintillation detectors, 36 Cherenkov detectors and 3 muon underground stations with triggering energy  1 GeV with detecting area of 16 m2. Detectors on the periphery were spaced 1km. Detectors in the center of the array spaced 100, 250 and 500 m.

• Prof. Watson, Yakutsk, 1984 Prof. Cronin to visit Yakutsk array, 1986

• In total, at the end of the second phase the arrays consisted

• 110 scintillation detectors

• 36 Cherenkov detectors

• 24 muon detectors

• 43 channels for registration of air shower events

Third Phase (1994 - 2004):

• Third Phase (1994 - 2004):

• Increased total number of stations on the periphery up to 60.

• Muon underground detectors – 7, total area ~300m2.

• Cherenkov detectors – 50

• 550 independent channels for registration of air shower events

• Area of the array 13 km2

Fourth Phase (2004 - ):

• Fourth Phase (2004 - ):

• Mostly added new measurements within 500 m circle. Which are

• 3 tracking Cherenkov detectors 250, 300 & 500 m from center

• 8 ground scintillation detectors that measures pulse shape

• 4 underground scintillation detectors for registering muons E  0,1 & 1 GeV

• 35 channels for direct measuring of Cherenkov light by differential detectors

• 12 antennas to register air showers radio emission

• Transparency of the atmosphere monitoring, aerosols and electric field near ground level during clear sky and thunderstorms.

• Continued modernization of the array in order to improve precision of the measurements of all air shower components, including precision of determination of air shower arrival angle.

Part 1: Cosmic Rays Spectrum in the Energy Range 1015 – 1018 eV and its Interpretation

• Part 1: Cosmic Rays Spectrum in the Energy Range 1015 – 1018 eV and its Interpretation

• History of Yakutsk array

• Yakutsk array

• Cosmic ray spectrum

• Spectrum interpretation

• Part 2: Mass Composition of Cosmic Rays at Ultra High Energies

• Methods for estimating mass composition

• Mass composition of Cosmic rays data interpretation (recent results)

Air shower

• Air shower

• 1016 – 1020 eV

• 61,7° N, 129,4° E

• 110 m above sea level

Part 1: Cosmic Rays Spectrum in the Energy Range 1015 – 1018 eV and its Interpretation

• Part 1: Cosmic Rays Spectrum in the Energy Range 1015 – 1018 eV and its Interpretation

• History of Yakutsk array

• Yakutsk array

• Cosmic ray spectrum

• Spectrum interpretation

• Part 2: Mass Composition of Cosmic Rays at Ultra High Energies

• Methods for estimating mass composition

• Mass composition of Cosmic rays data interpretation (recent results)

Table 1. Primary experimental data

• Table 1. Primary experimental data

• n/n lgQ(100) lgQ(200) lg(300) lgF lgNs(0) lgN(0) Xмах  lgk

• 1 6,01 - 11,42 5,80 4,91 560 205 3,94

• 2 6,17 - 11, 6,26 5,25 590 188 3,92

• 4 6,73 - 12,11 6,59 5,49 610 185 3,90

• 5 6,91 6,42 12,32 6,76 5,62 634 182 3,89

• 6 7,06 6,58 12,42 6,95 5,76 670 186 3,86

• 7 7,18 6,70 12,58 7,11 5,88 634 188 3,89

• 8 7,31 6,82 12,68 7,23 5,97 670 190 3,86

• 9 7,48 6,97 12,82 7,38 6,08 670 192 3,86

• 10 7,56 7,09 12,90 7,42 6,16 634 195 3,89

• 11 7,69 7,19 13,00 7,63 6,26 655 198 3,87

• 12 7,82 7,28 13,10 7,79 6,38 674 201 3,86

Table 2. The energy transferred to the different components of the EAS.

• Table 2. The energy transferred to the different components of the EAS.

• n/n lgEei lg Eel lg Em lg Ehi lg(Emi + Ev) lgE0

• 1 15,687 14,506 14,840 14,465 14,721 15,823

• 2 15,830 14,612 14,951 14,608 14,832 15,961

• 3 16,064 14,876 15,175 14,842 15,056 16,195

• 4 16,345 15,199 15,410 15,123 15,291 16,471

• 5 16,540 15,362 15,506 15,318 15,387 16,650

• 6 16,797 15,726 15,783 15,575 15,664 16,916

• 7 16,874 15,851 15,899 15,652 15,780 17,002

• 8 17,014 16,001 16,015 15,792 15,896 17,139

• 9 17,116 16,122 16,081 15,894 15,962 17,238

• 10 17,208 16,269 16,173 15,986 16,054 17,334

• 11 17,297 16,435 16,306 16,075 16,187 17,436

• 12 17,374 16,538 16,358 16,152 16,239 17,512

• 13 17,480 16,646 16,410 16,000 16,291 17,600

• 14 17,570 16,758 16,456 16,348 16,337 17,700

The simulation accounts:

• The simulation accounts:

• threshold of the detector

• fluctuations of background illumination

• Follows criterion:

• Time difference between signal from 3 stations that make up equilateral triangle must be ≤2,5 µs.

To estimate the precision of the measured characteristics of air showers complete simulation of model QGSJET was performed, which takes into account the instrumental and methodological errors and fluctuations in the development of air showers. The simulations was performed for the winter atmosphere near Yakutsk. For optical measurements we used real transparency of the atmosphere, which directly measured at the array.

• To estimate the precision of the measured characteristics of air showers complete simulation of model QGSJET was performed, which takes into account the instrumental and methodological errors and fluctuations in the development of air showers. The simulations was performed for the winter atmosphere near Yakutsk. For optical measurements we used real transparency of the atmosphere, which directly measured at the array.

• According to the space between stations, each triangle effectively selects showers in its energy range, but on threshold of each interval the efficiency of selection of events is disrupted and this affects the calculation of the spectrum intensity. This is so-called transition effect. Here is the transition effect is the transition from one type of trigger system which selects air showers with lower energy to another that selects air showers with higher energy.

• As shown by simulations, the impact of the transition effect in this case was reduced from 30% to 17% due to corrections to the collecting area of EAS events, which increased to high-energy showers and therefore overstated by the same amount the intensity of the cosmic ray spectrum.

Part 1: Cosmic Rays Spectrum in the Energy Range 1015 – 1018 eV and its Interpretation

• Part 1: Cosmic Rays Spectrum in the Energy Range 1015 – 1018 eV and its Interpretation

• History of Yakutsk array

• Yakutsk array

• Cosmic ray spectrum

• Spectrum interpretation

• Part 2: Mass Composition of Cosmic Rays at Ultra High Energies

• Methods for estimating mass composition

• Mass composition of Cosmic rays data interpretation (recent results)

• Following the idea that SNR are the sources of CR [3], K. Kotera [4] performed calculations for the three propagation model and

• Galactic, Metagalactic component of CR in the Universe. The purpose of these calculations was the interpretation of

• experimental spectrum in the energy range 1015 – 1018 eV, obtained from small arrays. And in particular, an attempt to explain

• the formation of second knee as the birth and spread of cosmic rays in the galaxy and beyond.

Experimental data on CR spectrum obtained recently in compact arrays, indicate the existence of irregularities in the spectrum of the second CR (second knee) at energy 21017 eV.

• Experimental data on CR spectrum obtained recently in compact arrays, indicate the existence of irregularities in the spectrum of the second CR (second knee) at energy 21017 eV.

• Over the observation time (20 years of continuous observations at Yakutsk Small Cherenkov Detector) and event statistics of air showers with energy above 1017 eV advance confirmation of existence of second knee most succeeded in Yakutsk, observing spectrum of Cherenkov "flashes" on the small Cherenkov array. There is reason to assume that the observed physics of the first and second breaks in the spectrum associated with astrophysical processes occurring both within our Galaxy, so beyond. Relatively smaller difference  between first and second break points can be explained by the transition boundary from galactic metagalactic to CR.

• Most possible sources of CR in the energy range 1015 – 1018 eV can be supernova remnants (SNR)

Part 1: Cosmic Rays Spectrum in the Energy Range 1015 – 1018 eV and its Interpretation

• Part 1: Cosmic Rays Spectrum in the Energy Range 1015 – 1018 eV and its Interpretation

• History of Yakutsk array

• Yakutsk array

• Cosmic ray spectrum

• Spectrum interpretation

• Part 2: Mass Composition of Cosmic Rays at Ultra High Energies

• Methods for estimating mass composition

• Mass composition of Cosmic rays data interpretation (recent results)

Method 1:

• Method 1:

• A joint analysis of the average characteristics of the longitudinal development of the EAS and their fluctuations: Xmax, σ(Xmax), dE/dXmax

• Conclusion: Gradual increase of protons energy in the range: 3∙1017 – 3∙1018 eV.

• [1] Dyakonov, M. N., Egorova V. P., Knurenko S. P. et al. Proc. of science papers. Yakutsk, 1987, p. 29-56 (in Russian).

• [2] Dyakonov, M. N., Egorova V. P., Ivanov A. A., Knurenko S. P. et al. //Proc. of AS USSR, phys. ser., 50, 11, 1986, p.2168 – 2171.

• [3] Dyakonov M.N., Egorova V.P., Ivanov A.A., Knurenko S.P., et.al. //20th ICRC, Moscow, 1987, v.6, p. 147-150.

• Method 2:

• Comparison of distribution asymmetry of Xmax at different energies by subtraction method.

• Conclusion: According to the Yakutsk array data in the energy ~1017 – 1019 eV observed systematic increase in the fraction of protons 60±10%

• M. N. Dyakonov, V. P. Egorova, A. A. Ivanov, S. P. Knurenko, V. A. Kolosov, S. I. Nikolsky, V. N. Pavlov, I. Ye. Sleptsov. // JETP letters (1989), 50, 10, p. 408-410.

Method 3:

• Method 3:

• Experimental data are compared with theoretical predictions of models QGSJET in the case of different primary nuclei with criterion χ2. χ2 determined by:

• 2(Хm) =  (Nexp(Хmax) - Ntheory(Хmax))2 / Ntheory(Хmax), (1)

1. S.P. Knurenko, A.A. Ivanov, V.A. Kolosov et al. // Intern. Jour. of Modern Physics A, V.20, №29, (2005), p. 6894 – 6897.

• 1. S.P. Knurenko, A.A. Ivanov, V.A. Kolosov et al. // Intern. Jour. of Modern Physics A, V.20, №29, (2005), p. 6894 – 6897.

• 2. S. P. Knurenko, A. A. Ivanov, I. Ye. Sleptsov. //Bull. RAS. Phys. ser. 2005, 69, № 3, p. 363 – 365.

• 3. S.P. Knurenko, V.P. Egorova, A.A. Ivanov et al. // Nucl. Phys. B (Proc. Suppl.). 151 (2006), р. 92-95.

Dependence of fraction of muons from track length in individual showers

• Dependence of fraction of muons from track length in individual showers

• (θ = 0 – 50°, E≥1018 eV)

1. S. P. Knurenko, A. K. Makarov, M. I. Pravdin, A. V. Sabourov. Bul. RAS, phys. ser., 2011, 75, 3, p. 320 – 322

• 1. S. P. Knurenko, A. K. Makarov, M. I. Pravdin, A. V. Sabourov. Bul. RAS, phys. ser., 2011, 75, 3, p. 320 – 322

• 2. S.P. Knurenko, I.T. Makarov, M.I. Pravdin, A.V. Sabourov. Proc. XVI International Symposium. Chicago. 2010. arXiv: 1010.1185v1 [astro-ph. HE]

Method 6:

• Method 6:

• Evaluation of the mass composition by the maximum depth of air shower Xmax and model QGSJETII 03. Interpolation method.

Part 1: Cosmic Rays Spectrum in the Energy Range 1015 – 1018 eV and its Interpretation

• Part 1: Cosmic Rays Spectrum in the Energy Range 1015 – 1018 eV and its Interpretation

• History of Yakutsk array

• Yakutsk array

• Cosmic ray spectrum

• Spectrum interpretation

• Part 2: Mass Composition of Cosmic Rays at Ultra High Energies

• Methods for estimating mass composition

• Mass composition of Cosmic rays data interpretation (recent results)

Scenario 1:

• Scenario 1:

• Within the interval 3∙1017 - 3 ∙1018 eV the shape originates from unknown component (possibly – from the interaction of CR with galactic wind and shock re-acceleration)

• Above 3∙1018 eV – from meta-galaxy

• Scenario 2:

• Supernovae play a certain role in generation and subsequent acceleration of CR up to energy ~1018 eV

Long-term observations at Yakutsk array shows:

• Long-term observations at Yakutsk array shows:

• There are 2 features in the spectrum of CR in the energy range 1015 – 1019 eV. It can be assumed that these features are the result if:

• Heavy component of CR for example iron escaping from our galaxy

• Indicates an increasing role of metagalactic CR

• Thank you for your attention!