THIRTY FIVE YEARS OF THE YAKUTSK EAS ARRAY

The 4th International Workshop on

THE HIGHEST ENERGY COSMIC RAYS AND THEIR SOURCES

 INR, Moscow

Important! The planned dates of UHECR workshop were May 22-24, 2008. Unfortunately, because of the circumstances we cannot control (General Meeting of the Russian Academy of Sciences) we have to shift workshop to May 20-22, 2008.

(just before the Quarks-2008 Seminar)

Program with links to presentations

• development of the atmospheric showers
• energy determination
• primary composition
• arrival directions
• origin and propagation of the UHE particles
  
• hadronic models

Preliminary list of talks

Click on the title to see abstract.

• Vladimir Aynutdinov, Status of Baikal neutrino experiment Coathors: BAIKAL Collaboration
• Konstantin Belov, Search for the UHE neutrinos high above the Antarctic ice shield - The ANITA experiment
• Leonid Dedenko, The cosmic ray luminosity of the nearby active galactic nuclei Coathors: Fedorova G.F., Podgrudkov D.A., Roganova T.M.
  Our analysis shows that the nearby AGN are hardly to be accepted as possible sources of the most energetic cosmic rays.
• Askhat Gazizov, Diffusion of ultra high energy particles in expanding universe Coathors: R. Aloisio and V.S. Berezinsky
  Generalization of Syrovatsky solution to calculation of diffuse UHECR flux in expanding universe will be discussed for different types of intergalactic magnetic fields.
• Oleg Kalashev, Ultra-High Energy Cosmic Rays and the GeV-TeV Diffuse Gamma-Ray Flux Coathors: Dmitry Semikoz, Gunter Sigl
  Ultra-high energy cosmic ray protons accelerated in astrophysical objects produce secondary electromagnetic cascades during propagation in the cosmic microwave and infrared backgrounds. We show that such cascades can contribute between 1% and 50% of the GeV-TeV diffuse photon flux measured by the EGRET experiment. The GLAST satellite should have a good chance to discover this flux.
• Boris Khrenov, TUS/KLYPVE program for observation of Extreme Energy Cosmic Rays from Space Coathors: TUS/KLYPVE
  Abstract: At present the extreme energy cosmic rays (EECR, E> 5 10^19 eV) are studied by ground- based array (The Pierre Auger observatory, the Telescope array) with exposure factor expected in 10 years of about 10^5 km^2 sr year. For collecting data on events with energies >>10^20 eV the exposure of 10^7 km^2 sr years is needed. Such an exposure could be achieved only in global observation of the Earth atmosphere from space. Technology of space experiments already started to be developed in the space experiment "Universitetsky-Tatiana". It will be followed by the space EECR experiment "TUS". The large area mirror- concentrator and a photo receiver are being developed for the next space experiment KLYPVE at the Russian segment of ISS. In parallel the technology of sofisticated two lens optical system and fine structered large photo reciver are being developed in the JEM EUSO project. The JEM-EUSO detector will allow to observe the atmosphere with factor 10^6 km^2 sr year. In the next decade the space experiments will mature and start to be an effective tools of EECR study.
• Pavel Klimov, Searching for asymmetry of arrival directions of Extreme Energy Cosmic Rays with the space detectors TUS, KLYPVE, JEM-EUSO Coathors: O.Kalashev, B.Khrenov, S.Sharakin, S.Troitsky
  We calculate quantitavely for the space-based detectors (TUS, KLYPVE, JEM-EUSO) the strength of anisotropies assosiated with two model of the UHECR origin: the extragalactic model and the superheavy dark-matter one.
• John Matthews, The Telescope Array (TA/TALE) experiment Coathors: TA Collaboration, TALE Collaboration
• Sergey Ostapchenko, Muon component of high energy air showers: puzzles and prospects Recent data on muon production in high energy extensive air showers are discussed in comparison with the corresponding theoretical predictions. Possible solutions of the reported discrepances are investigated and the relevance of forthcoming accelerator experiments is discussed.
• Sergey Ostapchenko, High energy radiation from Centaurus A Coauthors: M.Kachelriess, R.Thomas
• Dmitry Podgrudkov, The time pulses of signals in scintillator detectors from extensive air showers with energies above 10**8 GeV Coathors: Dedenko L.G., Fedorova G.F., Roganova T.M.
  The time pulses of signals in the scitillator detectors are estimated with help of CORSIKA code at various distances from the shower core. The time width of a signal at 600m from the shower cored does not exceed the value of 2000 ns while at larger distances it may increase up to 4-5 mks. This can affect the lateral distribution function. The energy estimate with the signal s(600)is 1.6-1.7 lower than adopted by the Yakutsk Collaboration.
• Vasily Prosin, Study of Primary Cosmic Rays with EAS Cerenkov Light in Tunka Valley (Tunka-25 and Tunka-133 arrays) Coathors: Tunka Collaboration
  The methods of measurement of primary energy and EAS maximum depth (Xmax) have been developed for Tunka-25 experiment. These methods provide the uncertainty of absolute primary energy measurement better than 10%, the energy resolution less than 15% and the accuracy of Xmax about 25 g/cm^2. The preliminary results of these methods use for the processing of the new Tunka-133 array are presented.
• Grigory Rubtsov, Timing-related observables for UHECR composition studies Coathors: D.S. Gorbunov, S.V. Troitsky
  We study several timing-related observables for different primary particle types and hadronic models. Full account of shower fluctuations is provided by using the library of showers simulated without thinning.
• Artem Sabourov, Extensive air shower estimates and the possibility to obtain the UHECR mass composition Coathors: M.I. Pravdin
  UHECR mass composition is very important for the problem of searching for their origins. In the energy region above 10^17 eV one has to compare experimentally measured air shower parameters and their fluctuations to predictions made by model calculations for different primaries. At the Yakutsk EAS array, besides surface detectors measuring charged component of the shower, there are several underground muon detectors. This enables us to obtain EAS characteristics by different components, thus extending instrumentalities for composition studies.
  In recent work (A.V.Glushkov, I.T.Makarov, M.I.Pravdin et al, Pis'ma v ZhETF, 87, 220-224, 2008) it was determined by muon part in EAS, that at energies higher than 10^19 eV there is a significant contribution to cosmic ray composition from heavy nuclei near Fe. In this paper we analyze the slope of lateral distribution function for charged particles in individual events with energy above 10^17 eV. We compare experimental data with calculations for different primaries within different hadron interaction models to obtain similar estimation of mass composition. We're also looking for possibilities to obtain more precise conclusions when simultaneously utilizing several parameters measured in individual events.
• Dmitri Semikoz, Constraining the cosmic ray source spectrum from observations in the GZK regime We present a method to constrain the injection spectrum of ultrahigh energy cosmic rays (UHECRs) from supposedly identified extragalactic sources, which can be applied even when only one or two events per source are observed, and is more efficient than a simple fit of the UHECR energy spectrum including only the contribution of all identified sources. The method is based on the analysis of the probability for a given source to populate different energy bins, depending on the actual CR injection spectral index. In particular, we show that for a typical source density of 4*10^{-5}/{Mpc}^{3}, a data set of 100 events above 60 EeV allows one in 97 % of the cases to distinguish a source spectrum dN/dE ~1/E^{1.1} from one with 1/E^{2.7} at 95% confidence level.
• Pierre Sokolsky, HiRes experiment Coathors: HiRes Collaboration
  The High Resolution Fly's Eye (HiRes) collected ultra high energy cosmic ray data between 1997 and 2006. The experiment observed cosmic ray showers via air fluorescence. The observatory consisted of two observatory stations separated by 12.6 km which measured cosmic rays in monocular mode. The data from the two stations can also be combined to form a stereo measurement of the showers. The experiment measures such properties as the energy spectrum, chemical composition, and p-air cross-section of these cosmic rays. It also searches for point sources and other anisotropy. The most recent measurements from this mature detector will be presented.
• Yuri Stenkin, On the PRISMA project (proposal) A new type of an array for EAS study will be presented. PRImary Spectrum Measurement Array (PRISMA) project is proposed with the aim to solve the "knee" problem. The array will be based on absolutely new methodical principles developed in the INR RAS. The main role will be given to the hadronic component detectors. It is well known that hadrons are the main EAS component while all others are secondary ones. That is why only hadrons could give us a key to solve the "knee" problem. The primary energy region for the PRISMA will cover a wide range from ~ 10 TeV to ~30 PeV. Primary spectrum as well as mass composition is expected to be measured precisely by different methods in the frames of this project.
• Gordon Thomson, Comparing Cosmic Ray Showers to Simulations Coathors: HiRes Collaboration
  The HiRes experiment has produced a considerable amount of detailed data on the development of extensive air showers from ultrahigh energy cosmic rays. The HiRes Collaboration also has considerable experience in simulating air showers and the response of our detectors to them. In this talk I will present a comparson of the properties of real and simulated showers.
• Peter Tinyakov, On the interpretation of the cosmic-ray anisotropy at ultra-high energies Coauthors: D.S. Gorbunov, I.I. Tkachev, S.V. Troitsky
  A natural interpretation of the correlation between nearby Active Galactic Nuclei (AGN) and the highest-energy cosmic rays observed recently by the Pierre Auger Collaboration is that the sources of the cosmic rays are either AGN or other objects with a similar spatial distribution (the ``AGN hypothesis''). We question this interpretation. We calculate the expected distribution of the arrival directions of cosmic rays under the AGN hypothesis and argue that it is not supported by the data, one of manifestations of the discrepancy being the deficit of events from the direction of the Virgo supercluster. We briefly discuss possible alternative explanations including the origin of a significant part of the observed events from Cen A.
• Igor Tkachev, Ultra-High Energy Cosmic Ray production in the polar cap regions of black hole magnetospheres. Coauthors: A. Neronov, D. Semikoz
  We develop a model of ultra-high energy cosmic ray (UHECR) production via acceleration in a rotation-induced electric field in vacuum gaps in the magnetospheres of supermassive black holes (BH). We show that if the poloidal magnetic field near the BH horizon is misaligned with the BH rotation axis, charged particles, which initially spiral into the BH hole along the equatorial plane, penetrate into the regions above the BH "polar caps" and are ejected with high energies to infinity. We show that in such a model acceleration of protons near a BH of typical mass 3e8 solar masses is possible only if the magnetic field is almost aligned with the BH rotation axis. We find that the power of anisotropic electromagnetic emission from an UHECR source near a supermassive BH should be at least 10-100 times larger then UHECR power of the source. This implies that if the number of UHECR sources within the 100 Mpc sphere is ~100, the power of electromagnetic emission which accompanies proton acceleration in each source is comparable to the typical luminosities of active galactic nuclei (AGN) in the local Universe. We also explore the acceleration of heavy nuclei, for which the constraints on the electromagnetic luminosity and on the alignment of magnetic field in the gap are relaxed.
• Sergey Troitsky, Physical conditions in potential UHECR accelerators Coathors: Sergey Gureev, Ksenia Ptitsyna
  We discuss updated constraints on UHECR accelerators ("Hillas plot" plus energy losses) for different acceleration mechanisms and with the most recent observational data on the accelerator parameters. In particular, we analyze, object-by-object, physical conditions in active galaxies correlated with Auger events and estimate whether it is possible to accelerate protons or nuclei to the observed energies there.
• Serguei Vorobiov, The status, results and the future prospects of the Pierre Auger Observatory Part I Coathors: The Pierre Auger Collaboration
  The new generation cosmic ray detector, the Pierre Auger Observatory (PAO) in Argentina consists in large aperture (exceeding 7000 km2 sr above 1019 eV) hybrid detection (combining air fluorescence and ground particle techniques) of the same extensive air showers (EAS) induced by a primary particle in the atmosphere. The project aims at covering the UHECR sky completely with two observation sites, one in the Southern and the other in the Northern hemisphere. While the Southern Auger Observatory is now nearing its completion, the intensive preparation work for the Northern Observatory has been performed. The hybrid measurements allow to improve significantly the precision on reconstructed primary cosmic ray parameters, and to cross-calibrate between the two techniques at the energies, unreachable with accelerator experiments. After description of detector performances, I will present and discuss the Auger results of the anisotropy search at small and large angular scales. The particular attention will be drawn to the observed correlation between the highest energy cosmic rays and the Active Galactic Nuclei.
• Serguei Vorobiov, The status, results and the future prospects of the Pierre Auger Observatory Part II Coathors: The Pierre Auger Collaboration
  The second of two lectures on the Pierre Auger Observatory results will be dedicated to the UHECR energy spectrum measurements, and the studies of the cosmic ray composition. The large data set collected by the Auger detector, and the used hybrid detection techniques allow the Auger measurements to gain in precision, in covered energy range, and in better control of systematic errors, compared to the previous experiments. This will be demonstrated on the example of two energy spectrum measurements, one based on the Surface Detector (SD) data, and the other obtained from the data set of hybrid events. Concerning composition studies, I will start with an overview of the mass-sensitive observables accessible with Auger. The focus will be made on the SD observables, sensitive to the longitudinal shower development, namely the signal risetime and the curvature of the shower front. The method based on these observables allowed to derive upper limits on the fraction and the flux of photons in the UHECR. The Auger SD array, with its nearly 100% duty cycle, is also sensitive to the ultra-high energy Earth-skimming tau-neutrinos, and an upper limit on the diffuse flux of the tau-neutrinos has been obtained. After completion of the Surface Detector, the construction of the Southern Observatory Enhancements will start, in order to extend the hybrid measurements down to the 1017 eV and to investigate the transition from the Galactic to extragalactic cosmic rays. The Enhancements will include high elevation fluorescence telescopes, and a dense surface array equipped with muon detectors.

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