Non-imaging Air Cherenkov Technique for studies of Cosmic Ray Origin and Gamma- astronomy. L.A.Kuzmichev (SINP MSU) On behalf on the Tunka and SCORE Collaboration February, 2011

Abstract Non-imaging Air Cherenkov Technique is described by using the Tunka-133 array and the SCORE project as an examples. The Tunka-133 is a 1 km 2 array started to operate in autumn of 2009 in the Tunka Valley, 50 km from the Lake Baikal. The main goal of the array is to study energy spectrum and mass composition in the energy range of eV. SCORE is a project of 10 km 2, low threshold array. The main goal is to search of gamma-quanta with energies above 30 TeV (origin of cosmic rays) and to study cosmic rays with energies of up to eV. It is planned that the first stage of SCORE ( 1-2 km 2 ) will be installed in the Tunka Valley for joint operation with the Tunka-133 array.

OUTLINE 1.Non-imaging Air Cherenkov Technique 2. Tunka-133: construction and deployment. 3. Results after first season. 4. Plan for the Tunka-133 upgrading. 5.SCORE project. 6. Cherenkov Technique at Mounting Level

20-30km P, A For E e >25 MeV V e > C/ n – light velocity in air Cherenkov light Photons detectors Q tot   N(x) dx ~ E Atmosphere as a huge calorimeter E (PeV) = 0.4 Q(175) ph· ev -1 cm -2 Lateral Distribution Function

Advantage of Cherenkov Technique: 1. Good energy resolution - up to 15% 2. Good accuracy of X max g/cm 2 3. Good angular resolution – 0.3 deg 4. Low cost – Tunka-133 – 1 km 2 array: $ ( construction and deployment) $ ( PMTs) Disadvantage: 1. Small time of operation ( moonless, cloudless nights) – 5-10%

Energy threshold of Cherenkov array Signal noise = S Q ph (175)    S I ph  T 3 3 E th ~  I ph  T  S  for S =0.1 m 2 и  0.1 : E th  100 TeV S– area of PMT photocathode  - quantum efficenty Q ph (R) –Cherenkov light flux T - duration of pulse ( 20 –40 нс)  - angle of view I ph – light night background  ph/cm 2 s Q ph (175 ) = C · E Light background

Usage of Cherenkov Light Lateral Distribution Function (LDF) for the Reconstruction of EAS Parameters light flux at core distance 175 m - Q 175  Energy P = Q(100)/Q(200) X max LDF from CORSIKA Q(R) = F(R, p) (only one parameter) Experimental data fitted with LDF steepness of LDF

Lg(Q(175) / ph· ev -1 cm -2 ) Energy determination: E = C· Q(175) 094 Lg( E/E 0 ) CORSIKA Energy resolution ~ 15% Cherenkov light density at 175 m from the shower core

Absolute calibration of energy measurement 1. To measure light flux with good accuracy we need to know PMTs quantum efficiency and light attenuation. Difficult but possible. 2. Another approach – how to avoid measurement of quantum efficiency and light attenuation - experiment QUEST at Gran-Sasso. E Q(175)

Experiment QUEST – QUSARS at EAS-TOP EAS-TOP array at Gran-Sasso (Italy) – N e and core position. Cherenkov detectors – LDF and P =Q(100)/Q(200) For P we not need to know the absolute value of quantum efficiency PMT QUASAR-370 ( 37 cm photocathode diameter) Used in Baikal Neutrino experiment NT200 and Tunka-25

p No dependence from Hadronic model

Model independent intensity of CR flux from QUEST experiment. Tunka experiment is normalized to this intesity.

X max determination 1.Steepness of LDF: X max = F( P) 2. Width of light signal : X max = F( τ ) 3. Shape of Cherenkov front : X max = F(a) ( not used up to now) a

X max by steepness LDF H max (km ) = – 2.33 · P

. Dependence of pulse duration from the distance from the core for EAS with different Xmax ( CORSIKA + apparatus distortion) ( 1.  X= 154 г  см 2, 2  X= 555 г  см 2, 3.  X=877 г  см 2 ) X max by using WIDTH DISTANCE FUNCTION (WDF)  400  X =X 0  cos   X max ( X 0 – depth of the atmosphere lg  (R) Dependence of  X (X 0  cos   X max ) from  (400) WDF (R,  (400 )

Tunka-133 – 1 km 2 “dense” EAS Cherenkov light array Energy threshold eV Accuracy: core location ~ 6 m energy resolution ~ 15%  X max < 25 g∙cm -2 S  (Tunka-133) = 30  S  (Tunka- 25)

Search for the Acceleration Limit of Galactic Sources - Energy range eV demands: - 1 km² with spacing smaller than that at Auger - complementary techniques IceTop IceCube - KASCADE-Grande terminated - IceTop/IceCube 100% ready - Tunka-133 (calorimetric) in operation - NEVOD-DÉCOR in operation - Auger low energy extension 80% ready - SCORE planned -LHAASO planned CR from SNRCR from AGN ? Tunka-133

Tunka-133: 19 clusters, 7 detectors in each cluster Optical cable Cluster Electronic box DAQ center PMT EMI 9350 Ø 20 cm 4 channel FADC boards 200 MHz, 12 bit

Array deployment Optical cables Detectors Testing PMTs

4 channel FADC Cherenkov light pulses at two detectors of the cluster at core distance~ 700 m 1. ADC AD9430, 12 bit, 200 MHz 2. FPGA XILINX Spartan-3 t (  5 ns)

Optical detector of Tunka-133 PMT EMI 9350 Ø 20 cm Angular sensitivity

First season of operation: November 2009– March hours of good weather. > 2  10 6 events with energy  эВ.  10 events during every night with number of hitted detectors more than 100. Trigger counting rate during one night. Distribution of the number of hitted clusters in one event.  50 detectors  eV

Example of event Energy: 2.0  eV zenith angle : 12.6 ° 125 detectors R  lg ( I light ) Core position: LDF -method WDF -method

.A– Fitting experimental points with LDF B – Fitting of  ( R) with Width – Distance Function. A B Thershold Lg Q exp (R ) LDF WDF Lg  (R )

182 event 353 g1 g2 Combined spectrum Tunka 25( ) plus Tunka 133 ( ) g1 = 3.2 g2 = 3.0

353 events 277 Good pointing for the existing of “ bump” 4.2 

Tunka-133 Gamma

Plan for Tunka-133 upgrading -Far distant clusters for encreasing effective area - Scintillation muon counters E 0, X max ( from Tunka-133 ), N µ - Low threshold array

1 km. 6 additional clusters ( 42 detectors) Increasing Effective Area in 4 times for energy more than eV In operation Statistics in 2012 ( > eV) : 600 (inner events) (out events) All: 1400 events

SCORE project – wide-angle gamma-telescope with area km 2 and threshold  30 тэВ (M.Tluczykont et al, ArXiv: ) SCORE: Study for Cosmic ORigin Explorer First SCORE Station will be tested at Tunka in this summer Increasing area of PMT with Winston cone

Distance between station m Angular resolution: < 0.1°

The Physics Motivations: Cosmic Ray Origin Search for the Pevatrons: gamma-quanta with energy >100 TeV only from hadronic mechanism Propagation and Absorption of gamma-rays ( photon/axion conversion or Lorentz violation ) Dark matter Axion as CDM candidate

Cherenkov Technique at Mounting Level. For good energy resolution X max < X 0 ( depth of Atmosphere ) – “thick calorimeter”

Cherenkov Technique at Mounting Level 1.Low energy E < TeV 2. Large zenith Angle > 45°

LDF for 100 TeV gamma (zenith angle = 0°) Tunka level LHAASA level 2 times Difference seems not too dramatic but should take into consideration

X0X0 X 0 / cos 45 X max distribution For proton with energy eV

Very large area of muon detectors at LHAASO gives: 1.High factor of gamma-hadron separation for SCORE –like array. 2.Essential increasing of the accuracy of mass composition study at eV 3. Good sensitivity to ultra high energy gamma radiation

Muon number vs. Xmax AIRES 2.8.4a QGSJET-II E µ > 1 Gev, θ = 0°  Nµ /Nµ = 10%,  Xmax = 20 g/cm 2 p ( 500 events) He ( 500 events) Si (500 events) Fe ( 500 events) X max lgNµ lgNµ (corr)= lgNµ X max Fe, Si p, He

Search for diffuse gamma-radiation

766 г/см г/см 2 Log N mu

Search for diffuse gamma radiation at high energy

Conclusion 1. Non-imaging Air Cherenkov Technique is rather well understood technique. High energy resolution – %, high accuracy for X max - 20 g/cm 2 2. The TUNKA-133, presently the largest Air Cherenkov Array in the world, is operating now and provides very interesting results. The upgrading of the array will start in The SCORE is very perspective project for Very High Energy gamma-ray astronomy and Cosmic Rays physics. 4. Operation of SCORE and TUNKA like arrays (for large zenith angles) at the LHAASA altitude seems very interesting.

Thank You

Tunka Collaboration S.F.Beregnev, N.N. Kalmykov, E.E. Korosteleva, V.A. Kozhin, L.A. Kuzmichev, M.I. Panasyuk, V.V. Prosin, A.A. Silaev, A.A. Silaev(ju), A.V. Skurikhin, I.V. Yashin, A.V. Zablotsky – Skobeltsyn Institute of Nucl. Phys. of Moscow State University, Moscow, Russia; N.M. Budnev, A.V.Diajok, O.A. Chvalaev, O.A. Gress, A.V.Rjchanov, 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, B.A. Shaibonov(ju) – Institute 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

E 0 ~ Q (175 m) Ln(1/A) ~ X max X max 2. Signal duration ~ ΔX g/cm 2 ΔX = X 0 /cosθ – X max X0X0 θ, φ 1. Steepnes of LDF: P ~ H max, km H max =(T 0 /grad(T)((X max cosθ /X 0 )C/grad(T) - 1) – H arr )/cosθ Methods of X max measurement: Registration of Cherenkov light from EAS

Is there an “iron knee” above the classical knee at 3∙10 15 eV? What is the mass composition above a possible iron knee? Is this region dominated by the sources different to supernova remnants? Does “second knee” at eV exist? Is it caused by the end of the galactic component? Detailed study of cosmic rays energy spectrum and mass composition in the energy range –10 18 eV with Cherenkov light array of about 1 km 2 area The main aim of experiment:

No “bump” in Kaskade-Grande Spectrum ( arXiv: ) We need more statistic and knowing of mass composition

Energy spectrum (preliminary)

Time callibration

Amplitude calibration

Conclusion 1.The spectrum from to eV cannot be fitted with one power law index g : 3.2 to 3.0 at eV. 2. Very good agreement with KASKADE-Grande results ( up to 7  ). 3. For energy > eV we need much more statistics. 4. “Bump” at eV - possible indication of a bump + agreement with GAMMA. But not seen by KASKADE-Grande. 5. Spectrum and mass composition with 2 times more statistics will be presented at ICRC ( Beijing, 2011 ) 6.Update 2011: - Far distant clusters. - Net of radio antennas. - First SCORE detectors.

I = (2.3 ±0.1(stat)±0.4(syst.)) ·10 -7 m -2 s -1 ster -1

Methods for the core reconstruction and X max determination 1. By using Lateral Distribution Function (LDF) 2. By using Width Distance Function (WDF)