ultra high energy cosmic rays : 40 years retrospective of continuous observations at the yakutsk...

Ultra High Energy Cosmic Rays : 40 years Retrospective of Continuous Observations

at the Yakutsk Array. Part 1: Cosmic Rays Spectrum in the Energy Range

1015 – 1018 eV and its Interpretation

I. S. Petrov, S.P. Knurenko, Z.E. Petrov, I.Ye. Sleptsov

Yu. G. Shafer Institute of Cosmophysical Research and Aeronomy of SB RAS, Yakutsk, Russia

E-mail: [email protected]

mailto:[email protected]

ContentsPart 1: Cosmic Rays Spectrum in the Energy Range 1015 – 1018 eV and its InterpretationHistory of Yakutsk array

Yakutsk array

Cosmic ray spectrum

Spectrum interpretation

Part 2: Mass Composition of Cosmic Rays at Ultra High EnergiesMethods for estimating mass composition

Mass composition of Cosmic rays data interpretation (recent results)

History of Yakutsk arrayFirst phase (1969 - 1974):

The array was built on area of 3.5 km2 with 13 scintillation and Cherenkov detectors, spacing between detectors were from 500 to 1000 m. The array was triggered by air showers event with energy E ≥ 1017 eV.

Photo1: Head of the Yakutsk EAS

DD Krasilnikov & John Linsley

at the 4th European Symposium on Łódź, 1974.

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 consistedo 110 scintillation detectorso 36 Cherenkov detectorso 24 muon detectorso 43 channels for registration of air shower events

Third Phase (1994 - 2004): o Increased total number of stations on the periphery up to 60. o Muon underground detectors – 7, total area ~300m2.o Cherenkov detectors – 50 o 550 independent channels for registration of air shower eventso Area of the array 13 km2

Prof. Nagano, Yakutsk array (summer, 1994)

Fourth Phase (2004 - ):

Mostly added new measurements within 500 m circle. Which are

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

o 8 ground scintillation detectors that measures pulse shape

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

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

o 12 antennas to register air showers radio emission

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

o 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.


Yakutsk array

Cosmic ray spectrum




Yakutsk array

Air shower

1016 – 1020 eV

61,7° N, 129,4° E

110 m above sea level

Yakutsk Small Cherenkov array

Yakutsk array Cherenkov detectors


Yakutsk array

Cosmic ray spectrum




Measurements of Cherenkov light emission at Yakutsk array

Cherenkov light lateral distribution function. Q(150) and Q(400) classification parameters. EAS energy estimation

1015 1016 1017 1018 1019 1020105

106

107

108

109

1010

- 1- 2- 3- 4

Q(R

), p

hot/

m2

E0, eV

10 100 1000104

105

106

107

108

109

1010

1011

-Yak.data,E0=1016eV;E

0=1017eV;E

0=1018eV

-H.P.data,E0=1017eV; E

0=1018eV

-QGS,E0=1017eV; -E

0=1018eV,(Lagutin et all)

Q(R

),

[ p

hoto

n /

m2 ]

R, [ m ]

Cherenkov light lateral distribution (photon/m2)

Classification parameters.

1 – Q (150),

2 – Q (400)

Algorithm of the energy balancing method:

The primary energy of a shower at the Yakutsk EAS array is calculated by the expression E0 = Eei + Eel + E + Ehi + Ei + E The energy scattered by electrons in the atmosphere above the observation level is given by the expression Eei = k(x, P)F Here, F is the total flux of Cherenkov light from the EAS and k(x, P) is the coupling coefficient that represents the transparency of the real atmosphere and character of the longitudinal shower development. The energy of electrons at the observation level is calculated as Eel = 2,2106Ns(X0)eff where Ns(X0) is the total number of charged particles at sea level and eff is the absorption mean free path of shower particles obtained from the correlation of the parameters Ns(X0) and Q(R=400) at different zenith angles. Other components: E = N ; Ei = (0.12 0.09)E ; Ehi = (5.6 2.2)E; E = (0.64 0.18)E

Energy balance

• 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

Empirical estimate of the energy of EAS at Yakutsk array

• 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•

Events selection. Triggering system. The effective area of events selection.

4,5 5,0 5,5 6,0 6,5 7,0 7,5 8,0 8,53,0

3,5

4,0

4,5

5,0

5,5

6,0

6,5

7,0

log

10(S

eff

m2

)

log10(Q150/1 phton m-2)

Effective area of EAS registration as a function of the classification parameter Q(150)

Configuration of master combinations used at the small Cherenkov array

Simulation and measurement of the spectrum of CR by Yakutsk Small Cherenkov array.

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.

Configuration of master combinations used at the small Cherenkov array

Air shower characteristics measurement precision reached at the Small Cherenkov Yakutsk array

Е0, PeV (R), m Ns

(Q(100))phot./m2

(Q(200)phot./m2

(Q(400) phot./m2

(s(300))

1/m2

( s(600))

1/m2

2 9,7 0,15 0,17 1,3

10 7,2 0,11 0,15 1,0

100 15,5 0,27 0,15 0,25 5,7

200 34,6 0,32 0,20 0,20 0,22 0,25 5,4

1000 26,7 0,35 - - 0,20 0,17 0,19 3,3

lg(Eo), eV 15-15,3 15,3-15,6 15,6-15,9 16,3-16,6 16,6-16,9 17,3-17,6

б , m 12 10,7 9,4 8,2 6,7 5,1

бRoапп , m 21,93 8,66 13,75 16,34 7,58 11,35

бSапп 0,142 0,132 0,125 0,111 0,098 0,092

бNeапп /Nср 0,152 0,115 0,129 0,114 0,128 0,096

бXmапп, г/cm2 70,8 69,7 69,5 67,8 65 63,3

Conclusion

• 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.

Energy spectrum of cosmic rays obtained by the smallCherenkov setup at the Yakutsk array

CR spectra obtained at various compact EAS arrays:

1015 1016 1017 1018 1019

1024

1025

- Yakutsk last data

dI/d

E x

E3

[m-2

s-1sr

-1e

V3]

primary energy [eV]

1015 1016 1017 1018 1019

1024

1025

- Tynka last data

dI/d

E x

E3

[m-2

s-1sr

-1eV

3 ]

primary energy [eV]

1015 1016 1017 1018 1019

1024

1025 - KASKADE GRANDE last data

dI/d

E x

E3

[m-2

s-1sr

-1eV

3]

primary energy [eV]

1015 1016 1017 1018 1019

1024

1025

- GAMMA array

dI/d

E x

E3

[m-2

s-1sr

-1eV

3]

primary energy [eV]

1015 1016 1017 1018 1019

1024

1025

- Tibet 3 data

dI/d

E x

E3

[m-2

s-1sr

-1e

V3]

primary energy [eV]

Summary spectrum according to Yakutsk, Tunka, KASKADE Grande, Gamma and Tibet 3:


Yakutsk array

Cosmic ray spectrum




Possible sources forming part of the spectrum around knee

105 106 107 108 109 1010

102

103

104

105

I(E

)*E2

.7 m

-2s-1

sr-1

Ge

V1.7

E (GeV)

AD6, интерпретация knee

Contribution of CR from different SNR types and contribution of nearby individual sources to the all particle spectrum in the present model together with selective experimental data of small Cherenkov array to Yakutsk [1]. Results from [2].

1015 – 1016 eV – the shape of the spectrum due to the luminosity of nearby sources, like SNR in our galaxy (Erlykin,

Sveshnikova et al (2013)):

HB21, HB9, Cygnus Loop,Vela JR. 9, SN Iib, SN Ia, CC_SNR& Vela Jr

[1] S.P. Knurenko, A. Sabuorov. // Proc. 33rd ICRC, Rio De Janeiro, 2013. [2] L.G. Sveshnikova, E.E. Korosteleva, L.A. Kuzmichev et al. Nearby sources in the transition region between Galactic and extragalactic cosmic rays. // arxiv.org:1303.1713

http://arxiv.org/abs/1303.1713

Nearby sources in the transition region between Galactic and Extragalactic CR

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.

1015 1016 1017 1018 1019 1020

1024

1025

B - Galactic all particle spectrum, Exp. data - Yakutsk, KASKADE-GRANDE, TUNKA, HiRes, Agure

I(E

)xE

3

m-2s-1

sr-1e

V2

E, eV

[3] E.G. Berezhko, S.P. Knurenko, L.T. Ksenofontov. Composition of cosmic rays at ultra high energies. // Astroparticle Physics 36 (2012) pp. 31-36. [4] Kumiko Kotera and Martin Lemoine. Inhomogeneous extragalactic magnetic fields and the second knee in the cosmic ray spectrum. // arXiv: 0706.1891v2 [astro-Ph] 4Jan 2008.

Conclusion

• 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 21017 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)


Yakutsk array

Cosmic ray spectrum




Methods for estimating mass composition

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: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)

400 500 600 700 800 900 1000 1100 12000

10

20

30

40

50

60

70

80

90

100

110

120 Yakutsk data, 3*1017< E <8*1017eV

<E>=5*1017eV, n=505; QGSJET01, p(100%); CNO(100%); Fe(100%)

n,

[ nu

mbe

r of

eve

nts

]

X axis title

400 500 600 700 800 900 1000 1100 12000

20

40

60

80

100

120

140

160

180

200

220

240

QGSJET01, p(70%), Fe(30%)

Yakutsk data, 8*1017< E <2*1018eV,

<E>=1*1018eV, n=857; QGSJET)01, p(100%); CNO(100%); Fe(100%)

n,

[ nu

mbe

r of

eve

nts

]

Xmax

, [ g / cm2 ]

400 500 600 700 800 900 1000 1100 12000

20

40

60

80

100

120

140

160

180

Yakutsk data, 2*1018< E <3*1019eV,

<E>=5*1018eV, n=352; QGSJET01, p(100%), CNO(100%), Fe(100%)

n,

[ nu

mbe

r of

eve

nts

]

Xmax

, [ g / cm2 ]

Conclusion

Thus, the model QGSJET01 can assume that the mass composition of of PCR changes from the energy (5 30) 1017 to (3 ) 1018 eV. At E0 31018 eV PCR is ~70% proton and He, other nuclei in ankle region (~1019 eV) less than ~30% (10**19 эВ).

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.

Method 4:Multicomponent analysis using measurements of Cerenkov light and charged particles EAS

-2 -1 0 1 2 3-3

-2

-1

0

1

2

3

4

- Yakutsk data, E0=9,8*1017 eV

- (p + He), - (Si + Fe)

t

p-2 -1 0 1 2 3

-3

-2

-1

0

1

2

3

4


- Line(p+He), - Line(Si+Fe)

t

p

-2 -1 0 1 2 3-3

-2

-1

0

1

2

3

4


- (p+He), - (Si+Fe)

t

p

ConclusionThe analysis is performed for three energies 2,4∙1017 eV, 9,8 ∙ 1017 eV and 4,8 ∙ 1017 eV. Cloud of points reflects standardized values. Lines – reflects borders of these zones. In this case, line m1 & line m2 divides nuclei to groups (p + He), C and (Si + Fe).

[1]A. A. Ivanov, S. P. Knurenko, A. A. Lagutin, M. I. Pravdin, A. V. Sabourov, I. Ye. Sleptsov. Bul. RAS, Phys. ser., 2007, 71, 4, p. 467-469.[2]S.P. Knurenko, A.A. Ivanov, M.I. Pravdin et al. // Nucl. Phys. B (Pros. Suppl.), 175-176, 2008, p. 201 – 206.[3]A.A. Ivanov, S.P. Knurenko, A.A. Lagutin, R.I. Raikin and I.E. Sleptsov. Proc. Altay Univ. ,1, 2008, с. 63– 65.

Method 5: Analysis of the proportion of muons, depending on the length of the particles track in the atmosphere

Dependence of fraction of muons from track length in individual showers

(θ = 0 – 50°, E≥1018 eV)

Distribution of ρµ/ρch normalized to track length equal 500 g/cm2

according to the model EPOS (UrQMD)

ConclusionComparison of the distribution of muons share with the calculation results indicate a mixed composition at energies above 1018 eV. Large fluctuations in the relationship does not allow a good accuracy to allocate separate groups of nuclei and make them their opinion on the percentage. But the use of "pure" response of the muon detectors (calculations Dedenko et al 2010) leads to the conclusion that a lightweight composition at energies 1018 - 1019 eV.

1. S. P. Knurenko, A. K. Makarov, M. I. Pravdin, A. V. Sabourov. Bul. RAS, phys. ser., 2011, 75, 3, p. 320 – 3222. 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: Evaluation of the mass composition by the maximum depth of air shower

Xmax and model QGSJETII 03. Interpolation method.

1015 1016 1017 1018 1019 1020

-1,0

-0,5

0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

4,0

<lnA

>

E0, eV

Nature of the dependence of the <lnA> changes with increasing energy, reaching a maximum at (5 - 30) ∙ 1016 eV.

MC of CR is changing after the first break in the spectrum at ~3 ∙1015 eV Reaches more heavier nuclei in the energy range (3 - 30) ∙ 1016 eV. 3 ∙ 1017 eV MC become lighter.

E.G. Berezhko, S.P. Knurenko, L.T. Ksenofontov. //Astroparticle Physics 36 (2012) pp. 31-36. [S.P. Knurenko, A.V. Sabourov. //Astrophys. Space Sci. Trans., doi:10.5194/astra-7-251-2011


Yakutsk array

Cosmic ray spectrum




Comparison Yakutsk data with HiRes & Auger. Models QGSJETII-03 & SIBYLL 2.1. Calculation (Berezhko et al. 2012) for 2 scenarios

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

Thus, a combined analysis of the spectrum and CR MC with computational results doenst exclude the hypothesis of supernova – related origin of CR with energies up to 3 ∙ 1018 eV.

1012 1013 1014 1015 1016 1017 1018 1019 10200

1

2

3

4

5 Y2

<ln

A>

E (eV)

QGSJETII-04. 2013 The curves correspond to the 3 versions of the calculation of Kotera work.

Conclusion

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:

1.Heavy component of CR for example iron escaping from our galaxy

2.Indicates an increasing role of metagalactic CR

Thank you for your attention!

ultra high energy cosmic rays : 40 years retrospective of continuous observations at the yakutsk...

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energy range

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