"Tunka-133: Results of 3 Year Operation" Vasily Prosin (SINP MSU) For the Tunka Collaboration

OUTLINE 1. Tunka experiment geography and history. 2. Methods of data processing. 3. Primary energy spectrum. 4. Methods of Xmax measurement. 5. Mean Xmax and mean lnA. 6. Further experiments in Tunka Valley.

1 km 175 optical detectors PMT EMI 9350 Ø 20 cm 635

Lake Baikal shore in Kultuk – gate to Tunka valley

Tunka Valley, River Irkut

Tunka District National Park

History of the experiments in the Tunka Valley 1992 – 4 PMTs QUASAR-370 on the ice of Lake Baikal. 1993 – 1995 – Tunka-4 – 4 PMTs QUASAR-370 in Tunka Valley. 1995 – ICRC in Roma, La Sapienza University. Start of the first International Collaboration with Gianni Navarra and A.M. Hillas. 1996 – 1999 – Tunka-13 – 13 PMTs QUASAR-370 1998 – 2000 – QUEST (5 PMTs QUASAR-370 at EAS-TOP in LNGS). 2000 – 2003 – Tunka-25, S = 0.1 km2 in Tunka Valley. 2004 – 2009 – Creating of Tunka-133 – 133 PMTs from former MACRO experiment (Idea of Gianni Navarra), S = 0.7 km2. 2011 – Expanding of Tunka-133 – 175 PMTs , 6 distant clusters, S = 2.5 km2.

Start of the Tunka experiments

Tunka Collaboration S.F. Beregnev, N.N. Kalmykov, N.I. Karpov, E.E. Korosteleva, 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 Institute of Nucl. Phys. of Moscow State University, Moscow, Russia; N.M. Budnev, O.A. Chvalaev, O.A. Gress, A.V. Dyachok, E.N. Konstantinov, A.V. Korobchebko, R.R. Mirgazov, L.V. Pan’kov, Yu.A. Semeney, A.V. Zagorodnikov, Institute of Applied Phys. of Irkutsk State University, Irkutsk, Russia; B.K. Lubsandorzhiev, N.B. Lubsandorzhiev, Institute for Nucl. Res. of Russian Academy of Sciences, Moscow, Russia; V.S. Ptuskin, IZMIRAN, Troitsk, Moscow Region, Russia; Ch. Spiering, DESY-Zeuthen, Zeuthen, Germany; A. Chiavassa, Dip. di Fisica Generale Universita' di Torino and INFN, Torino, Italy. S.N. Epimakhov, D. Horns, M. Tluczykont Hamburg University, Hamburg, Germany

Search for the Acceleration Limit of Galactic Sources Subtask: Fill the gap between the knee range and the giant arrays range. - KASCADE-Grande - IceTop/IceCube Tunka-133 IceTop IceCube Tunka-133 V.Ptuskin and V.Zirakashvili,2010 11

Primary nucleus E0 , A? E0 ~ Q(200) Cherenkov light flux Xmax(model independent): Two methods: ADF steepness (LDF replaced now ADF) Pulse width (FWHM replaced now by τeff ) θ, φ Xmax 2 X0 1

Single detector readout: Fitting of a pulse and measuring of the parameters: Q=c∙Spulse, Amax, ti , τeff=S/A/1.24 Spulse anode: ti Amax dinode:

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)-bQ steepness: bQ bA > bQ

ADF: Fore different functions in the different R ranges, but a single steepness parameter bA : R0, Rkn, c are the functions of bA A(R) = Akn·exp((Rkn-R)·(1+3/(R+2))/R0) A(R) = Akn·(Rkn/R)c A(R) = A(400)·((R/400+a)/(a+1))-b A(R) = A(400)·((R/400+1)/2)-b

Light flux Q(200) – energy measure Q(R) = Q(300)·((R/300+1)/2)-b

Recalculation from Cherenkov light flux Q200 to the primary energy E0 E0 = A·Q200g g = 0.94 CORSIKA simulation: ~ 500 protons ~ 500 iron Zenith angles: 0°, 30°, 45°

Absolute energy calibration : QUEST experiment (Cherenkov detectors at EAS-TOP) Integral spectrum p Normalization point for Tunka-133 P – LDF steepness (2000)

Single event example Plan ADF and LDF EAS time front τeff vs. core distance A ADF LDF

Experimental data 3 winter seasons: 2009-2010 , 2010-2011, 2011-2012 165 serene moonless nights ~ 980 h of observation with a trigger frequency ~ 2 Hz ~ 6 000 000 triggers The cuts for the energy spectrum used: θ ≤ 45° Rcore < 450 m: ~ 170 000 events with E0 > 6·1015 eV – 100% efficiency ~ 60 000 events E0 > 1016 eV ~ 600 events E0 >1017 eV Rcore < 800 m: ~ 1900 events E0 >1017 eV

Tunka-133 (2012) effective areas 450 m 800 m

Energy spectrum Reff < 450 m . 1 : 2 : 26 Z: p He Fe

Energy spectrum Reff < 450 m Primitive composition analysis in the knee (following A.Erlykin & A.Wolfendale): p – 14% He – 41% … Fe – 12% Unknown – 21% Conclusion: 1. He dominates in the knee. 2. Unknown component can not be extragalactic or it’s spectrum is different. 3. Fe domination is not close to 100% at 8·1016 eV. . knee He Fe p γ=-2.7 p? – unknown

Energy spectrum: power law fitting One can see two sharp features at the energies: ~2·1016 (first announced by KASCADE-Grande in 2010) and ~3·1017 (similar to that, announced by Yakutsk and Fly’s Eye in 90th) Statistics is insufficient at the tail so we use expanded effective area for E0 > 1017 eV .

Combined spectrum . Reff>800 m

Combined spectrum . The power law index at E0>1017 is similar to that obtained by the Giant Experiments: TA, HiRes, Auger.

Combined spectrum: comparison with some other works . Agreement with KASCADE-Grande Agreement with old Fly’s Eye, HiRes and TA spectra.

Two methods of Xmax measurement. ADF and WDF: R<250 m R<450 m

ΔXmax by b (ADF) steepness) CORSIKA SIMULATIONS (Correlations are model independent) ΔXmax by b (ADF) steepness) ΔXmax by τeff(400) (τeff = S/A/1.24) ~ 500 events – 107 GeV < E0 <108 GeV, θ = 0°, 30°, 45° green – proton, red - iron

PHENOMENOLOGICAL APPROACH: τeff(400) vs. zenith angle E0 = 3·1016 eV ~3500 events: 16.4 < log10(E0/eV) < 16.5  cosθ  ΔXmax = X0/cosθ – Xmax X0 = 965 g·cm-2 Supposed: <Xmax> = 580 g·cm-2 for E0 = 3·1016 eV

PHENOMENOLOGY: Xmax by τeff(400) CORSIKA ∆Xmax = 3344 – 1624∙log10(τ400), g∙cm-2

PHENOMENOLOGICAL APPROACH: ADF steepness vs PHENOMENOLOGICAL APPROACH: ADF steepness vs. zenith angle E0 = 3·1016 eV ~3500 events: 16.4 < log10(E0/eV) < 16.5  cosθ  ΔXmax = X0/cosθ – Xmax X0 = 965 g·cm-2 Supposed: <Xmax> = 580 g·cm-2 for E0 = 3·1016 eV

PHENOMENOLOGY: Xmax by the ADF steepness CORSIKA ∆Xmax = 2865 – 3519∙log10(bA-2), g∙cm-2

Experimental estimation of Xmax measurement errors Difference of Xmax derived from ADF steepness bA and τeff(400) σapp = σmes/√2 More exactly: σb = 25 g·cm-2, στ=30 g·cm-2 The main is ADF method having better accuracy and lower energy threshold

<Xmax> vs. E0 For <Xmax> estimation the events with the difference: Xmax-ADF – Xmax-τ > 3σ are excluded

EXPERIMENTAL Xmax DISTRIBUTIONS

ANALYSIS of Xmax DISTRIBUTIONS PRELIMINARY (the final version will be presented by S.Epimakhov at ICRC) Fit with weighted sum of 4 group MC simulated distributions: Fe, CNO, He, p

Xmax DISTRIBUTION in the last 3 points

Analysis of Xmax DISTRIBUTION PRELIMINARY (the final version will be presented by S.Epimakhov at ICRC) Fit with weighted sum of 4 group MC simulated distributions: Fe, CNO, He, p We hope to get the partial group energy spectra from this analysis (to be presented at ICRC)

Agreement with HiRes-MIA and Auger results at 1017 – 1018 eV <Xmax> vs. E0 Agreement with HiRes-MIA and Auger results at 1017 – 1018 eV

EXPERIMENT: MEAN <lnA> vs. E0

EXPERIMENT: MEAN <lnA> vs. E0

Conclusions 1. The spectrum from 6.1015 to 1018 eV cannot be fitted with single power law index: γ = 3.23 ±0.01 6·1015 < E0 < 2·1016 eV. γ = 3.0 2·1016 < E0 < 3·1017 eV. γ = 3.33 ±0.15 E0 > 2·1017 eV. 2. Agreement with KASCADE-Grande results. 3. The high energy tail do not contradict to the Fly’s Eye, HiRes and TA spectra. 4. The Xmax do not contradict to that of HiRes-MIA and Auger data. 5. Composition change to heavy from 1016 to 3·1016, stay heavy to 1017 and start change to light from ~1017 eV

Further Experiments in Tunka Valley Tunka-REX (the next talk of D. Kostiunun) Tunka-HiSCORE (M.Kunnas poster, R.Wischnewski report) - Scintillation counters from KASCADE-Grande to measure Ne and Nμ

Scintillation counter of KASCADE-Grande (800х800х40) Underground container On surface hut

HiSCORE project – wide-angle gamma-telescope with area 100 km2 and threshold 30 TeV (M.Tluczykont et al , ArXiv: 0909.0445 and yesterday report) HiSCORE:Hundred i Square-km Cosmic ORigin Explorer Time schedule 1.First SCORE Station will be installed at Tunka in this summer-autumn 25 station at 2012 – 1 sq. km wide-angle gamma telescope Energy spectrum from 1014 - 1017 eV - compare with Tunka-25 and Tunka-133 results

Тunka-HiSCORE : wide-angle Cherenkov gamma-observatory Area : from 1 to 100 km2 FOV ~ 0.6 ster ( ± 30° ) Energy threshold ~ 20 TeV Total cost ~ 50 ·106 Euro HiSCORE – Hundred* i Square-km Cosmic Origin Explorer

Calibration light source 4 PMTs Station Electronics

Thank You!