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Tunka-133: Cosmic Ray Mass Composition at 10 16 – 10 18 eV

Tunka-133: Cosmic Ray Mass Composition at 10 16 – 10 18 eV. Vasily Prosin (SINP MSU) For the Tunka Collaboration. Tunka Collaboration.

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Tunka-133: Cosmic Ray Mass Composition at 10 16 – 10 18 eV

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  1. Tunka-133: Cosmic Ray Mass Composition at 1016 – 1018 eV Vasily Prosin (SINP MSU) For the Tunka Collaboration

  2. Tunka Collaboration S.F. Beregnev, S.N. Epimakhov, N.N.Kalmykov, E.E.Korosteleva, N.I. Karpov, V.A.Kozhin, L.A.Kuzmichev, M.I.Panasyuk, E.G. Popova, V.V.Prosin, A.A.Silaev, A.A.Silaev(ju), A.V.Skurikhin, L.G. Sveshnikova, I.V.Yashin –Skobeltsyn Inst. of Nucl. Phys.of Lomonosov Moscow State Univ., Moscow, Russia; N.M.Budnev, A.V. Dyachok, O.A. Chvalaev, O.A.Gress, A.V. Korobchenko,R.R. Mirgazov, L.V.Pan’kov, Yu.A.Semeney,A.V. Zagorodnikov –Inst. of Applied Phys. of Irkutsk State Univ., Irkutsk, Russia; B.K.Lubsandorzhiev, B.A. Shaibonov(ju) –Inst. for Nucl. Res. of Russian Academy of Sciences, Moscow, Russia; V.S.Ptuskin –IZMIRAN, Troitsk, Moscow Region, Russia; Ch.Spiering, R.Wischnewski –DESY-Zeuthen, Zeuthen, Germany; A. Chiavassa –Dip. di Fisica Generale Universita' di Torino and INFN, Torino, Italy. D. Besson, J. Snyder, M. Stockham – Department of Physics and Astronomy, University of Kansas, USA

  3. Tunka-133 (update 2011)

  4. CORSIKA: Simulated lateral distributions and fitting function (LDF) E0 ~ Q1750.93 LDF has a single variable parameter of shape - steepness: P=Q(100)/Q(200) 0 < R < 700 m Q(R) = Qkn·exp((Rkn-R)·(1+3/(R+3))/R0) Q(R) = Qkn·(Rkn/R)2.2 Qkn R0 = 102.95-0.245·P [m] Rkn = 109 - 24.5·(P-4) [m] b = 4.84 - 2.83∙log10(6.5-P) Rkn 1 - P=5.0 2 – P=4.1 3 – P=3.2 Q175 Q(R) = Q(200)·((R/200+1)/2)-b

  5. An example of real shower of 16.03.2010 The limits for distances used now to unify Xmax analysis for all energy range: WDF FWHM(400) – analysis LDF P – analysis

  6. 3. The new methods of analysis for high core distances LDF LDF steepness analysis

  7. EXPERIMENT:Every event = 7 – 133 pairs of records: The primary data record for each Cherenkov light detector containes 1024 points of amplitude vs. time with the 5 ns time step: • Pulse selection • Apparatus distortions correction • Pulse waveform fitting anode dynode

  8. EXPERIMENT: The main parameters determination – area (light flux)Qi, amplitudeAi, width FWHMiand front delay ti at 0.25Ai. (The more accurate FWHM = τeff/1.24, τeff = Qi/Ai) ti FWHMi anode Ai dynode

  9. CORSIKA: Core location – LDF and ADF Core location: Amplitude – Distance Function (ADF), ADF tail fit: A(R) = A(400)·((R/400+1)/2)-bA steepness: bA LDF tail fit: Q(R) = Q(300)·((R/300+1)/2)-bQsteepness: bQ bA > bQ

  10. Accuracy of the EAS core reconstruction For R< 450 m: ΔRcore ~ 10 m For 450 m < R < 800 m: ΔRcore ~ 20 m for ADF method and ΔRcore ~ 30 m for LDF method

  11. CORSIKA: EAS Cherenkov light front tfront = (R+200)2/S Δθ < 0.5° for Nclusters > 4

  12. Recalculation from Cherenkov light flux Q200tothe primary energy E0 E0 = A·Q200g g = 0.94 CORSIKA simulation: ~ 500 protons ~ 500 iron Zenith angles: 0°, 30°, 45°

  13. Zenith angular distribution for E0 > 2·1016 eV

  14. CORSIKA: Xmax reconstruction ∆Xmax = 2767 - 3437∙log10(bA-2), g∙cm-2

  15. PHENOMENOLOGICAL APPROACH:Experimental LDF steepness vs. zenith angle for E0 = 3·1016 eV ~3500 events: 16.4 < log10(E0/eV) < 16.5  cosθ ΔXmax = X0/cosθ – Xmax X0 = 965 g·cm-2 <Xmax> = 570 g·cm-2 for E0 = 3·1016 eV

  16. PHENOMENOLOGY: Xmax reconstruction ∆Xmax = 2870 – 3520∙log10(bA-2), g∙cm-2

  17. Example of internal event

  18. Shower front

  19. Example of external event

  20. Shower front

  21. Plan Lightdistribution Shower front Pulse width

  22. Plan Lightdistribution Shower front Pulse width

  23. Plan Lightdistribution Shower front Pulse width

  24. anode dynode

  25. anode dynode

  26. anode dinode

  27. Experimental data 3 winter seasons 2009-2010, 2010-2011 and 2011-2012 165 clean moonless nights ~ 980 h of data acquisition with trigger rate ~ 2-3 Hz ~7 000 000 events Zenith angle θ≤ 45°, Rcore < 450 m: ~ 170 000 events with E0 > 6·1015 eV – 100% efficiency ~ 62 000 events with E0 > 1016 eV ~ 590 events with E0 >1017 eV Zenith angle θ≤ 45°, Rcore < 800 m: ~ 1800 events with E0 >1017 eV – 100% efficiency ~ 150 events with E0 > 3·1017 eV ~ 8 events with E0 >1018 eV

  28. Mean Depth of EAS maximum Xmax g·cm-2PRELIMINARY

  29. EXPERIMENT:Mean logarithm of primary mass.PRELIMINARY

  30. Mean logarithm of CR atomic number Berezhko 2009 CRs from SNRs + reacceleration + Extragalactic CRs Yakutsk Experiment: ATIC-2 (Panov et al. 2006) JACEE (Asakimori et al. 1998) KASKADE (QGSJET, SIBYLL) (Hörandel 2005) HiRes (QGSJET, SIBYLL) (Abbasi et al. 2005) CRs from SNRs +CRs from AGNs Accurate determination of CR composition at ε= 1017- 1019 eV is needed to find transition from galactic to extragalactic CR component

  31. CONCLUSION • Primary mass composition changes from light (He) at the knee to heavy at 3·1016 eV • The mass composition is heavy till at least 1017 eV • More statistics is needed at the energy range 1017 – 1018 eV • PLANS • More statistics. • The new simulations. • Xmaxdistribution analysis.

  32. Thank you!

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