PoS(ICRC2021)713 International th 12–23 July 2021 July 12–23 37 SICS CONFERENCE SICS CONFERENCE Berlin | Germany Berlin Berlin | Germany Cosmic Ray Conference Ray Cosmic ICRC 2021 THE ASTROPARTICLE PHY ICRC 2021 THEASTROPARTICLE PHY https://pos.sissa.it/ ONLINE on behalf of the TAIGA ∗ 1,2, and P.A.Volchugov ∗ 1, E.B.Postnikov ∗ 0,1, [email protected], , [email protected] [email protected] International Cosmic Ray Conference (ICRC 2021) Presenter ∗ th The 2nd TAIGA imaging air Cherenkov telescope (IACT) hasin successfully been the put into Tunka operation Valley incompletion. fall 2020. The ability Currentlyby to three taking more use into telescopes the account are telescopes theexceeding under unusually in the large construction the inter-telescope distance and so-called distances between them in stereoand (from conventional mode discussed. IACT 320 of stereo m The image systems, results to analysis of is 500from the being m), the dedicated well explored 1st Monte and Carlo the are 2nd compared TAIGA-IACT. with the experiment data [a]Joint Institute for Nuclear Research, Joliot-Curie 6,[b]Lomonosov Dubna, Moscow Moscow State Region, University 141980, Skobeltsyn Russia Institutegory of Nuclear 1(2), Physics GSP-1, Moscow, (MSU 119991, SINP), Russia Leninskie [c]Institute of Applied Physics, Irkutsk StateRussia University (API ISU), Gagarin Blvd. 20,E-mail: Irkutsk, 664003, Copyright owned by the author(s) under the terms of the Creative Commons © Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). 37 July 12th – 23rd, 2021 Online – Berlin, Germany Collaboration (a complete list of authors can be found at the end of the proceedings) A.A.Grinyuk, Stereoscopic and monoscopic operation of thein five the IACTs TAIGA experiment PoS(ICRC2021)713 > per pixel) with a point spread function of 0.07 > A.A.Grinyuk, E.B.Postnikov and P.A.Volchugov 2 (0.36 > total area), and a focal length of 4.75 m. The imaging camera for the 1st 2 Location of the HiSCORE stations along with IACTs in the Tunka Valley Figure 1: Optical design of the IACTs is of Davies-Cotton type with 34 spherical mirror tiles, each with The TAIGA experiment, where TAIGA stands for Tunka Advanced Instrument for cosmic For gamma-ray detection, TAIGA uses imaging air Cherenkov telescopes (IACTs) and wide- Currently two imaging air Cherenkov telescopes are operating, and the 3rd one has already been 2. TAIGA-IACTs a 60-cm diameter (9.6 m IACT comprises 560 photomultipliers (PMTs) with aof 19-mm 595 diameter; PMTs. for the The 2nd FoV IACT of it the consists camera is 9.6 [2]. ray physics and Gamma-ray Astronomy, combines detection(>100 of TeV) and both ultra-high-energy very-high-energy cosmic gamma rays raysin (>10 TeV) the at the Tunka Valley same near Tunkaobservation Astrophysical Lake times Center Baikal on the [1,2]. sources with The large declinations. northernmost location ofangle TAIGA timing allows stations long named TAIGA-HiSCORE (Highinformation Sensitivity from Cosmic the stations ORigin (arrival Explorer). directionno The and other IACT core detects position) the same will event. betelescopes However, some used and portion by analyzed of an events with will IACT a be even technique detected if by known multiple as stereoscopy. installed but with neither mirrorsis nor planned camera in due fall to 2021; COVID-19 theIACTs work 4th will restrictions. and be at 5th Its least IACT 250 will deployment m beand – installed peripheral that in ones. is 2 the years. distance The between distance the between central the IACT of the group (IACT#4) Stereoscopic operation of IACTs in TAIGA 1. Introduction PoS(ICRC2021)713 B8I4 at an 2 and reaches a maximum of 0.9 km 2 A.A.Grinyuk, E.B.Postnikov and P.A.Volchugov 3 10 times lower than that of single events both in the ∼ around the central telescope (TAIGA-IACT04). A total of 2 km 3 ∼ correspond to the Crab Nebula observation in the Tunka Valley. Photon bunches is the total number of photoelectrons (p.e.) in the image [9]. The counting rate ◦ –40 (8I4 ◦ events were generated for MC data bank. Based on these data, for each 5 TeV bin, the 5 We present the effective installation area for different types of analyzed events. It was obtained To estimate the effective area, MC simulation of a setup with 5 telescopes was used. Showers The first test sources selected for observation were the Crab Nebula and Mrk 421. Both these Simulation of extensive air showers (EAS) was carried out in CORSIKA [5] version 7.35 with Photoelectron data are input for the detector response simulation, which includes triggering After passing the hardware trigger, the events can be analyzed in several stereo modes, such as To verify the equivalence of simulation and experimental data, distributions of the image 10 · energy of 22 Above TeV. this energy,become the more registration extended efficiency and does are not rejected increase, by since the the cut at events the boundary pixels of camera. that for 2+ events at 10 the TeV, effective area is 0.45 km 4 number gamma-initiated events was calculated. At thebins same that time, passed the the number trigger of was eventscontaining calculated. in the boundary Note same that pixels from of the camera eventscomplex that were task. passed excluded, the since trigger, The events the ratio analysisthrough the of of trigger such the multiplied events by number the is of areainstallation a of in generated scattering more a particles of given gamma energy to rays range. gives the the effective number area of of the particles passed were scattered over area of for the events detected by the both2a). (Fig. telescopes were constructed based on real data and Monte Carlo simulated samples and in the experiment. 4. Effective area of events detected by the both telescopes is sources were successfully detected [3,4] inof the the preliminary 1st IACT. data analysis of stand-alone operation 3. Monte-Carlo simulation and comparison with experimental data QGSJET-II-04 [6] model forinteractions. high-energy interactions and Positions GHEISHA-2002d ofprotons [ 7] five and for TAIGA-IACTs gamma were low-energy rays were used simulated.for in gamma Energy input rays, range files. was both 5–100 distributedangles TeV for according Showers 30 protons to from and exponential 2–50 primary spectrum TeV from with CORSIKA the output index were -2.6. ray-tracedprogram in models optical a Zenith properties dedicated of IACT C++ all the optical wayphotoelectrons to PMT simulation at photocathodes program and the outputs IACT [8]. individual camera. This and analog readout procedures [8].by the Trigger signal decision in is two adjacent at PMTs exceeding in of one the cluster set of 28 threshold2 PMTs (10 +, within p.e.) 3 the +, set 4 time + window. and2 5. or more For telescopes. example, the 2+ mode means that the analysis involves events that triggered Stereoscopic operation of IACTs in TAIGA PoS(ICRC2021)713 (b) of events detected by the both B8I4 A.A.Grinyuk, E.B.Postnikov and P.A.Volchugov 4 Effective area of the TAIGA-IACT installation Figure 3: (a) Comparison of: a) experimental and MC distribution of Since the detection efficiency at low energies (a few TeV) is rather low, the analysis included First of all, it is necessary to take into account the suppression by the telescope hardware gamma rays and hadrons with energies abovemodeled 10 particles. The TeV. analysis In involves this applying chapter cuts we toof consistently show sets events. how of selected cuts influence on the selection Basic suppression trigger. For gamma rays above 10 TeV, 97% of the generated events pass the trigger, whereas the 5. Hadron suppression and sensitivity Figure 2: telescopes of the b)experimental TAIGA-IACT; distribution ofdetected size by of the all both events telescopes TAIGA-IACT01 and events Stereoscopic operation of IACTs in TAIGA PoS(ICRC2021)713 ) and ◦ , 8 9 ) leading to the loss of G ◦ p.e., are hereafter referred 8 18= Õ # 100 9 18= Õ # 1 18= 1 1 B8I4 > # + - number of triggered telescopes. = G 1 . The angular resolution for the 2+ events 0 CA86 B8=\, 68 = · # A <40= H H 2 8 A.A.Grinyuk, E.B.Postnikov and P.A.Volchugov 5 and B8I4 and B8I4 1 2 + 98 1 0 H 1 CA86 # 8 − − is necessary to improve the accuracy of determining the 9 18= 2 1 Í B8I4 Õ # 1 0 p.e. results in suppression coefficients of 0.6 for gamma and B8I4 = 8 18= Õ # G 100 18= 1 # = B8I4 > <40= G and gives suppression relative to the MC data bank of 0.4 for gamma > 10 TeV ◦ for hadrons > 10 TeV. is the number of histogram bins along the axis (equal for x and y). 4 = 0.2 − is the angle between intersecting lines [10], 18= 68 10 A # \ · We present the errors of determining arrival direction of events in the telescope’s FoV4). (Fig. Each pair of telescopes gives a point, which is filled into a histogram with a weight of After the trigger of the telescope, all events are divided into several parts, in accordance with The next step is to apply a cutApplication of to a the cut boundary pixels of camera. It leads to suppression When observing the known point sources of gamma rays, the direction of arrivalTo of solve this gamma problem, the arrival direction of particles was determined as the weighted average All the cuts described in this section, such as a hardware trigger, choice of the type of triggered The resulting direction of arrival of the event is determined as the average of the histogram where Cut on this value was definedbasic as suppression. a circle Further, with this containment parameter radii is 68% called of the events that passed the type is and 5 number of triggered telescopes(2+,procedure 3+ includes etc.). events of The 2+conservation further of type. 76% description of of The gamma rays the selection and hadron 23% of of suppression events hadrons detected from the incoefficients MC of this data 0.73 way bank. and leads 0.18 for to gamma the rays and hadrons, respectively. rays in the FoV of the telescopethe is source known, position which can is be incorrect useful for for hadrons. gamma-hadron separation. Hence, reconstruction of position of the intersectiontriggered points telescopes of will intersect the at major the point: axes of all ellipses. The image axes in the two the fraction of events outside the camera FoV. to as basic suppression. Determination of source location where events (2+, 3+ etc.), exclusion of boundary camera pixels and filled with the intersection points: 0.14 for hadrons. Cut onimage orientation. the image Stereoscopic operation of IACTs in TAIGA fraction of hadrons after thegamma hardware rays are trigger concentrated is in 51% athose due narrow of to region hadrons in the are the fact uniformly center that distributed of the over the the arrival camera entire FoV directions camera (within of (within 0.1 5 PoS(ICRC2021)713 ). 8 for 4 − B8I4 10 · 4+ (c) in a given triggered is the distance (angle) 2 and is determined so that ΔΩ F83Cℎ depends on the "width" and 8 - median absolute deviation,       ) and a given event size( B8I4 f ) ) 8 8 8 A is the ) 8 8 , B8I4 , B8I4 8 8 2 A A 2 Ω ( , B8I4 ( gives suppression of 0.38 and 4 8 f F83Cℎ < ΔΩ A ( F in minimization. This functional selects the 10 + "  2 − ª ® ¬ 2 Ω 8 depends on the 2 8 F f 2 ΔΩ 8 "  5 < A.A.Grinyuk, E.B.Postnikov and P.A.Volchugov \ 3+ Ω f 6 F Δ f ). (b) 8 A F83Cℎ 8 CA86 Õ # 8 © ­ « CA86 Õ # =       5 C4; 1 # = F is the median value of the width characteristic of events with a given is as close as possible to ) 2 8 2 8 8 \ typical for a given distance to the EAS axis( f Δ are template values predefined from the simulation. To determine these values, < Error of determining source location in telescope FoV for different event types. , B8I4 is the number of triggered telescopes, 8 F A F83Cℎ ( C4; 2+(stereo) < # and is the angles between the major axes of the ellipses and the lines connecting the center F (a) ) and distance to the shower axis( 2 8 8 \ Figure 4: Δ "  by weighted averaging ofdetermining intersection the points position of of the the source in major the axes telescope’s FoV, but of in the this case ellipses, the similar ellipses are to B8I4 F Another approach to determining the position of the source in the FoV of the telescope was In the stereoscopic approach, the normalized width is analogous to the "width" parameter[9]- Where • position of the source near thefrom intersection the of true the arrival major direction axes of of the events. ellipses The and cut at a small distance applied. It is based on minimizing the following functional: RMS along the minor axis of the ellipse. It is defined as11]: follows[ gamma rays and hadrons, respectively. Normalized width Stereoscopic operation of IACTs in TAIGA where of gravity (COG) of the image with the assumed position of the source, telescope, size( between the assumed position of"length" the source parameters and and the was true defined one.the in average The [10]. value of distribution of we need to reconstruct the core position. This was done in several ways: PoS(ICRC2021)713 60 <0 4 ∼ F 3587 19-52- # ) for gamma <10 92 ◦ 5 7454 2 . 0 ∼ ◦ 68 2 . A 0 = 113 8116 68 A number of for hadrons. Summary table events within 5 − 10 · 2 size > 11907 29384 100 p.e. A.A.Grinyuk, E.B.Postnikov and P.A.Volchugov for each interval of distances to the shower core, 7 for 100 h of observation) and northernmost location pixels 14389 39550 of edge ) and good angular resolution ( 1 exclusion 2 − s "  2 − l 1 km . Summary table of cuts influence 1 ∼ cm 2+ 1 − s and − events 14973 48784 2 − < TeV l cm 1 12 Table 1: − − 10 19128 trigger · 110354 TeV hardware 5 . 12 1 − ∼ m and grows with a decrease in the number of triggered telescopes up to 10 E) allow a detailed measurement of the energy spectra (>10 TeV) of many sources · ◦ 16 5 . gave suppression of 0.2 for gamma rays and MC = 1 19627 215765 0 ∼ generated '"( l < N, 103.04 ◦ located in the ground frame,case where of determining the the telescopes position are ofin located the a source relative nominal in to frame, the each the telescope joint other FoV, the FoV (in ellipses of the were theusing located telescopes); the procedure for minimizing the distances to the major axes of the ellipses [11]. On the basis of the obtained coefficients of suppression of hadrons and gamma rays, the The use of the later method improves the accuracy of determining core position. So, for 4+ Each of these approaches can be applied to the reconstruction based on: a) the major axes of Since fall 2021 three IACTs will be operating and available for the stereoscopic analysis. Two The work was performed at the UNU "Astrophysical Complex of MSU-ISU” (agreement A sufficiently large effective area ( • >10TeV gamma hadrons integral sensitivity of the TAIGA-IACT installationwas was estimated calculated. based on The the initial approximation number ofAs the of CR hadrons a spectrum of result, the DAMPE for observatoryobservation [12, gamma]. 13 rays with energies >10 TeV, we expect the sensitivity for 100 hours of m for 2+ events.with To determine a step of 100the m, distribution the of the dependence parameter of "normalizedthe these width" cut parameters was obtained on for the the sizedescribing simulated was the events. effect obtained. Using of cuts As on a simulated result, event samples is presented in1. Tab. events, the ellipses, b) theknown distance position parameter of [9] the source. - the distance between the COG of the image and the from the Crab Nebula and Mrk 501probably to SNR Dragonfly CTA Nebula, 1 Boomerang, and ARGO J2031+4157 Tycho. etc. and more IACTs are to be deployed by 2023. Acknowledgments 13.UNU.21.0007) and is supported by the Russian Foundation for Basic Research (grants Stereoscopic operation of IACTs in TAIGA rays with energy above 10 TeVBoth was the sensitivity derived ( from Monte Carlo(51.49 simulation of 5 IACTs in TAIGA. Conclusion PoS(ICRC2021)713 , Technical (2021) 362. , Tech. Rep. 84 ]. (2006) 380. Nucl. Instrum. Methods , ]. , vol. 3, p. 445, 1985. (1999) 135. 25 1010.1869 Journal of Physics: Conference 122 , (2021) 398–401. (2020) 262. 19-72-20067 (Sections 4, 5)), Russian . # 85 83 1909.12860 Physics of Atomic Nuclei , Monte Carlo Simulation of the TAIGA Hybrid Astropart. Phys. (2011) 014018[ A.A.Grinyuk, E.B.Postnikov and P.A.Volchugov , 8 (2019)[ 83 Astropart. Phys. 5 2105.09073 , , Sci. Adv. , Phys. Rev. D , Physics of Atomic Nuclei , Bull. Russ. Acad. Sci. Phys. Measurement of the cosmic-ray proton spectrum from 40 GeV to 100 161830. Gamma-Hadron Separation Methods for the VERITAS Array of Four , Detecting Gamma Rays with Energies Greater than 3–4 eV from the Cherenkov EAS arrays in the Tunka astrophysical center: From Measurement of the cosmic ray helium energy spectrum from 70 GeV to Comparison of techniques to reconstruct vhe gamma-ray showers from First detection of gamma-ray sources at TeV energies with the first 952 TAIGA—An Innovative Hybrid Array for High Energy Gamma Astronomy, Monte Carlo treatment of hadronic interactions in enhanced Pomeron CORSIKA: a Monte Carlo code to simulate extensive air showers The simulation of hadronic showers: physics and applications Cerenkov Light Images of EAS Produced by Primary Gamma Rays and by (2020) 012023. 19th International Cosmic Ray Conference (ICRC19) collaboration, 1690 , in Nuclei multiple stereoscopic Cherenkov images Imaging Atmospheric Cherenkov Telescopes Cosmic Ray Physics and Astroparticle Physics Gamma-Ray Experiment Physikalisches Institut, Technische Hochschule Aachen (PITHA) (1985). 80 TeV with the DAMPE space mission DAMPE TeV with the DAMPE satellite imaging air cherenkov telescope of the TAIGA installation Tunka-133 to the TAIGA gamma and cosmic ray hybrid detector scheme: QGSJET-II model Phys Res., Sect. A Series Report FZKA-6019, Forschungszentrum Karlsruhe (1998). Crab Nebula and Blazar Markarian 421the by TAIGA Imaging Experiment Atmospheric Cherenkov Telescopes in [9] A.M. Hillas, [1] N. Budnev et al., [8] E. Grinyuk, N. Postnikov and L. Sveshnikova, [2] L. Kuzmichev et al., [3] E. Postnikov et al., [5] D. Heck et al., [7] H. Fesefeldt, [4] L. Sveshnikova et al., [6] S. Ostapchenko, [10] W. Hofmann et al., Stereoscopic operation of IACTs in TAIGA 44002, 19-32-60003), Russian Science FoundationFederation (grant Ministry of Science and High Education (projects FZZE-2020-0017, FZZE-2020-0024). References [11] H. Krawczynski et al., [12] [13] F. Alemanno et al., PoS(ICRC2021)713 2 6 4 1 3 4 E. C. A. 1 8 Joint , V. V. 12 4 7 1 A. Pan 3 Novosibirsk I. I. Yashin 7 A. Chiavassa Space Science 17 4 3 A. A. Grinyuk , V. S. Samoliga 1 3 N. Ushakov V. A. Kozhin 3 9 , 1 4 10 A. V. Sokolov 4 E. B. Postnikov N. B. Lubsandorzhiev 5 12 A. L. Pakhorukov 1 N. M. Budnev D. P. Zhurov Institute for Nuclear Research, Y. I. Sagan 5 2 3 O. G. Grishin 3 1 3 A. Porelli M. Tluczykont M. Slunecka E. E. Korosteleva 1 16 1 2 National Research Nuclear University 2 Institut für Experimentalphysik, Universität E. A. Osipova T. I. Gress 0 M. Brueckner 3 E. V. Ryabov 1 3 1 R. Togoo 12 B. K. Lubsandorzhiev 9 , E. G. Popova 4 4 A. V. Zagorodnikov 14 5 A. V. Skurikhin K. G. Kompaniets 12 2 A. V. Bulan O. A. Gress Deutsches Elektronen-Synchrotron DESY, Zeuthen, 15738 4 9 5 , G. I. Rubtsov 4 M. Lavrova R. D. Monkhoev 1 3 L. G. Tkachev , M. Popesku 11 A.A.Grinyuk, E.B.Postnikov and P.A.Volchugov 3 13 3 9 R. Wischnewski Institute of Physics and Technology Mongolian Academy of Sciences, R. P. Kokoulin 12 6 A. N. Borodin 3 1 Max Planck Institute for Physics, Munich, 80805 Germany 10 A. Yu. Sidorenkov 3 1 1 A. Y. Razumov A. A. Lagutin R. Mirzoyan V. M. Grebenyuk 1 3 8 11 , 7 V. A. Poleschuk D. Voronin B. A. Tarashansky 2 M. Blank Budker Institute of Nuclear Physics, Siberian Branch, Russian Academy of Sciences, 3 11 8 3 S. N. Kiryuhin Altai State University, Barnaul, Altai krai, 656049 Russia 2 1 1 Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation, Russian R. I. Raikin 5 3 1 R. R. Mirgazov Research Institute of Applied Physics, Irkutsk State University, Irkutsk, 664003 Russia 3 L. A. Kuzmichev 3 A. A. Silaev(junior) N. V. Volkov A. Yu. Garmash 1 1 A. A. Petrukhin 1 3 V. A. Tabolenko 3 V. V. Kindin Dubna University, Dubna, Moscow oblast, 141980 Russia 1 9 1 P. A. Bezyazeekov Irkutsk National Research Technical University, Irkutsk, Russia 10 7 A. A. Pushnin 1 15 A. A. Silaev A. P. Kryukov D. S. Lukyantsev 3 L. V. Pankov A. R. Gafarov 8 , 1 P. A. Volchugov 3 7 12 A. K. Awad 7 2 N. N. Kalmykov Physics Department of the University of Torino and Istituto Nazionale di Fisica Nucleare, Torino, 10125 Italy L. G. Sveshnikova 6 10 5 V. S. Ptuskin 1 Skobeltsyn Institute of Nuclear Physics, Moscow State University, Moscow, 119991 Russia Institute, Magurele, 077125 Romania Academy of Sciences, Troitsk, Moscow, 142190 Russia Germany Ulaanbaatar, Mongolia 1 MEPhI, Moscow, 115409 Russia Institute for Nuclear Research, Dubna, Moscow oblast, 141980State Russia University, Novosibirsk, 630090 Russia Hamburg, Hamburg, D-22 761 Germany Russian Academy of Sciences, Moscow, 117312 Russia Novosibirsk, 630090 Russia A. N. Dyachok A. Kravchenko Spiering Vaidyanathan D. Horns A. D. Lukanov Yu. A. Semeney Stereoscopic operation of IACTs in TAIGA Full Authors List: TAIGA Collaboration I. I. Astapov M. I. Panasyuk Prosin