Interpretation of cosmic ray spectrum above the knee measured by the Tunka-133 experiment

Transcription

1 Interpretation of cosmic ray spectrum above the knee measured by the Tunka-133 experiment L.G. Sveshnikova, L.A. Kuzmichev, E.E. Korosteleva, V.A. Prosin, V.S. Ptuskin et al Moscow State University Skobeltsyn Institute of Nuclear physics

2 Outline Problems Tunka 25,133 method and results Comparison with other experiments Theoretical model of sources and Emax Origin of the Knee and transition region to Metagalactic Сonclusions

3 Problem From the theory we can expect the sequence of different types of dominating sources in different energy intervals and only a small number can accelerate to highest energies due to high value of required magnetic field and shock speed. Only very specific conditions of explosions and progenitor s history allows to get large Emax. IIp Ibc Ia? or IIb IIb? GRB? 100 TeV 1PeV 4 PeV 60 PeV Figure from V. Ptuskin, V. Zirakashvili, and Eun-Suk Seo, Astrophysical J. T. 718 p Transition from one type of dominating sources to other should reveals itself as a features in spectrum: knee, dip, peak.. So precise measurement of all particle spectrum and of partial nuclei spectra continue to be very important task.

4 PeV accelerated particle escape from SNR at years after explosion, so a chance to see directly gamma quanta from pevatron is very small.

5 175 optical detectors (EMI 9350) covering an area of 3 km 2 Tunka-133 a 3 km 2 Air Cherenkov Light Array R= 1 km 50 km from Lake Baikal, in Siberia In operation since 2009

6 Single detector: We measure the next parameneters of Cherenkov photon pulse through 5 ns: Q=c S pulse, A max, dt=, t i time delay with accuracy nsec Width of pulse S pulse anode: t i A max dinode:

7 Lateral distribution is approximated by 4 functions in every shower and Q200 and steepness parameter b is estimated A(R) = A kn exp((r kn - R) (1+3/(R+2))/R 0 ) A(R) = A kn (R kn /R) c A(R) = A(400) ((R/400+a)/(a+1)) -b A(R) = A(400) ((R/400+1)/2) -b

8 Recalculation from Cherenkov light flux Q 200 to the primary energy E 0 As a measure of energy we use the Cherenkov light flux density at a core distance of 200m - Q(200). It was found from CORSIKA. E 0 = A Q 200 g g = 0.94 CORSIKA simulation: protons iron nuclei Zenith angles: 0, 30, 45

9 Distance to the maximum of shower First method of X max reconstruction by parameter b Dependence of the relative EAS maximum position Xmax on log (b 2) X max = log 10 (b A -2), g cm -2

10 Distance to the maximum of shower Second method of Xmax reconstruction from width of pulse, (400m), width-distance method The -method uses the sensitivity of the pulse width at some fixed core distance to the position of the EAS maximum. This function was constructed on the basis of CORSIKA simulation the value of ( 400) is connected with the thickness of the atmosphere between the detector and Xmax (Xmax = X0/cos Xmax) by the expression: Log Pulse Width at 400 m Xmax = C D log e f f (400).

11 Distribution of Xmax in every energy interval is converted to partial spectra P, He, CNO, Fe Best fit (solid) for two different energy bins. The lines correspond to: proton (red dash), helium (pink), nitrogen (dagreen) and iron (blue). Xmax distribution in every energy bin was fitted as a superposition of weighted elemental distribution of 4 groups: p, He, CNO and Fe. For this analysis, partial Xmax distributions were simulated using CORSIKA 7.35 (2013) with QGSJETII-04/GHEISHA (S.N.Epimakhov et al. (Tunka Collaboration), 33th ICRC, Julym ID=0326.)

12 Experimental data 3 winter seasons of operation , , houre of good wether observation ~ triggeres For the analysis of mass composition only events with θ 40, R core < 500 m: ~ showers with E 0 > ev 100% efficiency ~ events with E 0 > ev ~ 600 events with E 0 >10 17 ev

13 Doi In press 1 knee hardening 2 knee

14 Spectra of P, He, CNO, Fe components Systematic errors are large!!

15 Comparison of light and heavy components with Kascade Grande : nuclei separation by Xmax in Tunka versus muon content of showers in KG Tunka: Kascade Grande W.D. Apel et al. [KASCADE-Grande Collaboration], Phys. Rev. D 87, (R) (2013)

16 IxE 3.0 m -2 s -1 s r-1 GeV 1.75 Str=F(E)/AE 3-1 Comparison with other experiments: agreement Tunka 133(2012), Kascade-Gr. Tibet 3 models 0,50 Structure=F(E)/AE ,25 0,00-0,25-0,50-0,75-1, E, GeV 3x10 6 Ice Top ,4 Gamma Structure F(E)/AE-3-1 2,5x10 6 2x10 6 1,5x StructF(E)*E 1 0,2 0,0-0, En, GeV -0, E GeV

17 Comparison: Common features 1. Sharpness and position of the knee at 4 PeV 2. Sharpness and position of the inverse knee (hardening) at 20 PeV 3. Sharpness and position of the second knee at 100 or 300 PeV (Tunka: 2 knee `300 PeV, Kascade Gr ~ closer to 100 PeV)

18 Features: knees, dips, peaks How they can be produced?

19 Integral spectrum by Z:N>Z Regidity dependent cutoff: Emax(Z)=ZEmax(H) d =lg(i Fe /I tot )/lg 26 ~ d ~0.6 (if Fe 13%) d ~ 0.5 (if Fe~20%) Integral abundance I(>Z) Hoerandel 1 TeV : P+He=60%: 0.30,0.30, 0.13,0.13,0.13 Hoerandel 1 TeV : P+He=60%: 0.20,0.40, 0.13,0.13,0.13 d = Z 32 ICRC, 2012, Beijing Change of gamma by corresponds to normal composition Normal composition one of the main signature of acceleration at the forward shock front of SNR

20 3.0 FxE Bump or dip or knee at the boundary of two decreasing and increasing components: : 10 7 d e m o Galactic CR- signature Extra Galactic CR d e m o d e m o 10 6 d e m o d e m o d e m o E (GeV)

21 Basic model of composition and Emax of Galactic sources at high energies: V. Ptuskin, V. Zirakashvili, and Eun-Suk Seo, Astrophysical J. T. 718 p Additionally we introduced: 1) a stochastic nature of sources, using Green function formalism sources are spread continuously in space and time 2) the condition that Emax for Core Collapsed SN is distributed from 1 0TeV to 3 PeV 3) Actual nearby sources from gamma catalogues L. Sveshnikova, O. Strelnikova, V. Ptuskin. Astropart. Phys. 2013, 50-52, pp 33-46

22 10 6 ATIC-2; Tibet QGSJet F(E)*E 2.7 m -2 s -1 sr -1 GeV Tunka-133; Calculation Kascade-Grande 10 4 CC_SNR SN Ia SN IIb E (GeV)

23 Source spectrum :Numerical simulations of diffusive shock acceleration in SNRs. From V.N.Zirakashvili, V.S.Ptuskin : Spectra of particles produced in the supernova remnant during yr. injected at the forward shock (thick solid line ),, spectrum of ions injected at the reverse shock (thic dashed line) 1 0,1 0,01 1E-3 C=d =3, =4 dgam=2, om=6 1E E GeV

24 1)The first version of explanation of the inverse knee at 20 TeV was presented in ECRS 2012: Knee is provided mainly by CR accelerated in SN_Ia or other group of sources with similar Emax. We can directly obtain the chemical composition if we suggest the nearly same slopes for species. In this case hardening at 20 PeV is produced by increase of heavy nuclei Tunka133 Tunka25 Kascade Gr. Kascade EASTOP Tibet Augergv Hires1M3 Hires2 Fe_Tunka Fe Kasc. Gr. It was shown: 1) Composition is enriched by Fe: P+He(~55-60) CNO(10%) Si-Ca(~10%),Fe (~20-25%) (Dark blue points) F(E) E Z 1 Z Z Z 14 Si 2) Source spectrum has a sharp cutoff Z 10 5 P He CNO E, GeV All

25 2013:New data from Tunka-133: the ratio of Fe was decreased essentially, so the hardening after 20 PeV is caused by the appearance of a new component F(E) E P+HE d e m o d e m o d e new m ofe d e m o E, GeV

26 After subtracting the contribution of CR provided the knee we have the rest that reminds most of all well known dip model 10 7 P+He HIRES F(E) E rest E, GeV

27 FxE 3.0 Extragalactic CR: Dip model (V. Berezinsky. (2013) arxiv: V. Berezinsky, et al Phys. Lett. B 612,147 (2005)+ magnetic horizon effect (M. Lemoine, Phys. Rev. D 71, (2005), R. Aloisio and V. Berezinsky, ApJ 625, 249 (2005)] [12] g=-2.7 Emax=10^22ev Calculations d e m o [15], db=2 e mng o Mod.2, lc=100, ns=10^-5 d emod. m o3, lc=30, d ns=10^-6 e m o Mod. 4, lc=100, ns=10^-5 d emod. m o1, lc=300, d ens=10^-5 m o Approximations in Fig.1 d e m o d e m o d e m o d e m o d e m o d e m o d e1 m o 2 d e3 m o d e m o d e m o K. Kotera and M. Lemoine arxiv: v2 Signature of e+e- pairproduction in interaction of UHE protons with CMB E (GeV) the diffusion time of particles with energy E < 10^17 ev from the closest sources (50 100Mpc) becomes longer than the age of the Universe. Low energy behaviour depends on mean strength of magnetic field B0=0.3-3 ng, coherence length lc ~ kpc, source density ns=10^-5-10^-6

28 Galactic - Extragalactic F(E) E 3.0 m -2 s -1 sr -1 GeV 2 EASTOP [18] Tibet [17] KASCADE[19] Tunka 25,133 [1] KASC. Gr [3] Ice Top [5] Model prediction Sum of Gal. + Extragal.: P+He Extragal. : Galactic : All P+He Z>6 Z>14 Z> E, GeV

29 F(E) E 3.0 m -2 s -1 sr -1 GeV EASTOP [18] Tibet [17] KASCADE[19] d etunka m o 25,133 d[1] e m o KASC. dgr. e 2012 m o [3] d Ice e mtop o [5] Model prediction Sum d eof mgal. o + Extragal.: d e m o 3 d2 e m o1 P+He d e m o Extragal. : Galactic : All P+He Z>6 Z>14 Z> CONCLUSION I E, GeV The all particle spectrum, light component and heavy component measured in Tunka- 133 can be described with the model when knee is produced by the special class of sources with ~ same Emax and approximately normal chemical composition, the extragalactic protons arises between 10^16 10^17 ev thus stressing the hardening of all particle spectrum at 20 PeV, the contribution of extragalactic protons reaches 50% of all particles around PeV.

30 Tunka <lna> -black full stars (2012); open stars (2013) 5 4 Kascade[24] MSU [25] ATIC2[22] Tunka 25,133 [2] [1] Jacee [23] Auger [26] Ice Top Model prediction 3, 2, 1, <ln A> % P+25% He E (GeV)

31 Nuclear component F(E) E 3.0 m -2 s -1 sr -1 GeV 2 5x10 6 4x10 6 3x10 6 2x10 6 Heavy Red-new 11June Model prediction Galactic : Z>6 Z>14 Z>20 Z>6 These points, if they are not of methodical reasons, are beyond the model. The systematic errors are very large Fe E, GeV

32 Defects 1. This model gives the dip only at proton or light composition of extragalactic CR!!! It assumes rightness of Hires and TA data, Auger data are in strong contradiction. 2. Dip and GZK cutoff can be modified by discreteness in sources distribution, by source local overdensity or deficit and by different value of Emax (V. Berezinskii)

33 Transition region from the numerous SNRs to the SNRs or other sources providing the knee is a very interesting region 10 6 ATIC-2; Tibet QGSJet F(E)*E 2.7 m -2 s -1 sr -1 GeV Tunka-133; Calculation Kascade-Grande 10 4 CC_SNR SN Ia SN IIb E (GeV)

34 P +He: Atic2, Argo, - Tunka the same slope as in all particle spectrum IxE 3.0 m -2 s -1 s r-1 GeV Tunka All Tunka P+He 10 6 Atic2, Argo P+He 10 5 Atic2 all Tunka P En, GeV

35 All Nuclei, Fe nuclei : Atic2->Tunka allnuc IxE 3.0 m -2 s -1 s r-1 GeV Atic 10 5 N>CNO N>Fe E0, GeV

36 CNO: from Atic 2 to Tunka IxE 3.0 m -2 s -1 s r-1 GeV Atic2 Atic En, GeV

37 Conclusion II 1. Group of sources providing the knee look like SNRs, because source spectrum and composition are in agreement with the standard model of acceleration by SNR forward shock. 2. But in the region PeV transition region from usual SNRs to rare sources providing the knee, we believe some new features in spectrum and composition will be found. 3. In the first 20 stations of Hiscore Tunka non imaging Cherenkov array starts to measure HE gammas and background cosmic rays

38 Nearby sources

39 3.0 FxE Cas A a very good candidate CAS A (SNR of IIb type - nearest ) Source d e mspectrum o d-2.02 e m o d e m o d e m o Emax=210^17 ev twice d e power m o for CR d eprod. m o d e m o d e m o Light composition Fe~2% Tunka 2011 Tunka2013 E (GeV) Many unusual properties from (J. Vink. arxiv: v2 ) J 1. Cas A must have been a Type IIb SNR, similar to SN1993J 2. Progenitor main sequence mass of 18±2M. 3. Strong bipolarity referred to as the jet. 4. Best explained with a binary star scenario, in which a high mass loss is caused by a common envelope phase. L.G. Sveshnikova, E.E. Korosteleva, L.A. Kuzmichev, et al, Journal of 408 Physics: Conference Series, 409, 1 (2013)012062; arxiv:

40 1) Sources spectrum: ~ , Emax ~ z (2 3)10 17, very light composition P+He~95%, Fe<2% 2) Closest sources should be at distance ~2-4 kpc, T < 100 ky 3) One source with usual power is enough, may be Cas A??? SNRIIb type

41 F(E)*E 2.7 m -2 s -1 sr -1 GeV Contribution of nearby sources ATIC-2; Tunka-133; Calculation around the knee Tibet QGSJet Kascade-Grande d e m o d e m o Vela Jr (0.3 kpc 0.7 ky) d e m o d e m o We could not exclude the single source But only Vela Jr. can provide the structure around the knee and only if : 1) Emax=F(Temission) 2) D~0.3 kpc, T~0.7 ky Cygnus Loop Vela Jr. (0.7 kpc 1.7 ky) HB9 d e m o d e m o HB E (GeV) It s very difficult to obtained high Fe content around 10^17 ev. Bachground sources also have high Fe content

42 Thank you!

43 10 7 HeJac 2.63 Tunka All IxE 3.0 m -2 s -1 s r-1 GeV 2.0 Tunka P+He 10 6 Atic2 all Atic2, Argo P+He En, GeV

44 10 7 IxE 3.0 m -2 s -1 s r-1 GeV allnuc Atic 10 5 N>CNO Fe Kascade N>Fe En, GeV

45 IxE 3.0 m -2 s -1 s r-1 GeV 2.0 CNO En, GeV

46 Mass composition