777 research outputs found
The UHECR-FR0 Radio Galaxy Connection: A Multi-Messenger Study of Energy Spectra/Composition Emission and Intergalactic Magnetic Field Propagation
This study investigates low luminosity Fanaroff-Riley Type 0 (FR0) radio
galaxies as a potentially significant source of ultra-high energy cosmic rays
(UHECRs). Due to their much higher prevalence in the local universe compared to
more powerful radio galaxies (about five times more than FR-1s), FR0s may
provide a substantial fraction of the total UHECR energy density. To determine
the nucleon composition and energy spectrum of UHECRs emitted by FR0 sources,
simulation results from CRPropa3 are fit to Pierre Auger Observatory data. The
resulting emission spectral indices, rigidity cutoffs, and nucleon fractions
are compared to recent Auger results. The FR0 simulations include the
approximately isotropic distribution of FR0 galaxies and various intergalactic
magnetic field configurations (including random and structured fields) and
predict the fluxes of secondary photons and neutrinos produced during UHECR
propagation through cosmic photon backgrounds. This comprehensive simulation
allows for investigating the properties of the FR0 sources using observational
multi-messenger data.Comment: PoS 444 (38th ICRC) 151
Progress in Monte Carlo design and optimization of the Cherenkov Telescope Array
The Cherenkov Telescope Array (CTA) will be an instrument covering a wide
energy range in very-high-energy (VHE) gamma rays. CTA will include several
types of telescopes, in order to optimize the performance over the whole energy
range. Both large-scale Monte Carlo (MC) simulations of CTA super-sets
(including many different possible CTA layouts as sub-sets) and smaller-scale
simulations dedicated to individual aspects were carried out and are on-going.
We summarize results of the prior round of large-scale simulations, show where
the design has now evolved beyond the conservative assumptions of the prior
round and present first results from the on-going new round of MC simulations.Comment: 4 pages, 5 figures. In Proceedings of the 33rd International Cosmic
Ray Conference (ICRC2013), Rio de Janeiro (Brazil). All CTA contributions at
arXiv:1307.223
Measurement of the cross section with the CMD-3 detector at the VEPP-2000 collider
The process has been studied in the
center-of-mass energy range from 1500 to 2000\,MeV using a data sample of 23
pb collected with the CMD-3 detector at the VEPP-2000 collider.
Using about 24000 selected events, the cross
section has been measured with a systematic uncertainty decreasing from 11.7\%
at 1500-1600\,MeV to 6.1\% above 1800\,MeV. A preliminary study of
production dynamics has been performed
Study of the process in the c.m. energy range from threshold to 2 GeV with the CMD-3 detector
Using a data sample of 6.8 pb collected with the CMD-3 detector at the
VEPP-2000 collider we select about 2700 events of the process and measure its cross section at 12 energy ponts with about
6\% systematic uncertainty. From the angular distribution of produced nucleons
we obtain the ratio
Улучшение теплогидравлических характеристик рекуперативных теплообменников с вторичными излучателями
У роботі представлені результати порівняльних експериментальних досліджень теплообміну і аеродинаміки в високотемпературних рекуператорах авторської та альтернативних конструкцій. Дослідження проводилися на вогневому стенді з метою порівняння характеристик дослідних секцій BD гладкотрубних петлевих рекуператорів і зразків з інтенсифікаторами теплообміну різної геометрії: 1) конструкцій SP зі спіральними вставками, встановленими по всій довжині теплообмінних труб(відносний крок спіралей = s/d = 4,0). Такі рекуператори відповідають існуючим закордонним аналогам; 2) конструкції MD авторської розробки з гнучкими хрестоподібними вставками – вторинними випромінювачами, встановленими по всій довжині теплообмінних труб. Визначенотеплотехнічні та теплогідравлічні переваги запропонованих рекуператорів типу MD порівняно іззакордонними конструкціями зі спіральними вставками – турбулізаторами і традиційними вітчизняними гладкотрубними рекуператорами.In frame of the presented work the results of comparative experimental investigations carried out on heat transfer and fluid dynamics processes within high temperature recuperators of the authors’ and alternative designs are discussed. The researches were fulfilled at firing rig with a purpose of comparison the characteristics of the test sections of smooth tube recuperator (BD) and the specimens with the facilities of different geometry providing heat transfer intensification: 1) the designs SP with the spiral inserts installed by the whole length of heat exchange tubes with the relative pitch of the spirals s/d = 4,0. These recuperators meetthe existing foreign analogous prototypes; 2) design MD of authors’ design with flexible cross-shaped inserts – the secondary emitters installed by the whole length of heat-exchange tubes. The heat engineering and combined heat and hydraulic advantages of proposed recuperators of MD type in comparison with the foreign designs with the spiral inserts – turbulators and with traditional native smooth-tube recuperators (BD) have been identified. It has been stated that especially appreciable results of the tests make the advantages of MD design regarding the most representative temperature criterion – temperature difference ΔTw-a between the tube walls and of an air flow. This value for authors’ design is decreased approximately 4 times in comparison with BD design and more than 2 times lower in comparison with that for foreign designs SP.В работе представлены результаты сопоставительных экспериментальных исследований теплообмена и аэродинамики в высокотемпературных рекуператорах авторской и альтернативных конструкций. Исследования проводились на огневом стенде с целью сравнения характеристик опытных секций BD гладкотрубных петлевых рекуператоров и образцов с интенсификаторами теплообмена различной геометрии: 1) конструкций SP со спиральными вставками, установленными по всей длине теплообменных труб (относительный шаг спиралей = s/d = 4,0). Такие рекуператоры соответствуют существующим зарубежным аналогам; 2) конструкции MD авторской разработки с гибкими крестообразными вставками - вторичными излучателями, установленными по всей длине теплообменных труб. Определены теплотехнические и теплогидравлические преимущества предложенных рекуператоров типа MD по сравнению с зарубежными конструкциями со спиральными вставками – турбулизаторами и традиционными отечественными гладкотрубными рекуператорами
Measurement of decay rate and parameters at KEDR
Using the inclusive photon spectrum based on a data sample collected at the
peak with the KEDR detector at the VEPP-4M collider, we
measured the rate of the radiative decay as well
as mass and width. Taking into account an asymmetric photon
lineshape we obtained keV, MeV/, MeV.Comment: 6 pages, 3 figure
A search for point sources of EeV photons
Measurements of air showers made using the hybrid technique developed with
the fluorescence and surface detectors of the Pierre Auger Observatory allow a
sensitive search for point sources of EeV photons anywhere in the exposed sky.
A multivariate analysis reduces the background of hadronic cosmic rays. The
search is sensitive to a declination band from -85{\deg} to +20{\deg}, in an
energy range from 10^17.3 eV to 10^18.5 eV. No photon point source has been
detected. An upper limit on the photon flux has been derived for every
direction. The mean value of the energy flux limit that results from this,
assuming a photon spectral index of -2, is 0.06 eV cm^-2 s^-1, and no celestial
direction exceeds 0.25 eV cm^-2 s^-1. These upper limits constrain scenarios in
which EeV cosmic ray protons are emitted by non-transient sources in the
Galaxy.Comment: 28 pages, 10 figures, accepted for publication in The Astrophysical
Journa
Reconstruction of inclined air showers detected with the Pierre Auger Observatory
We describe the method devised to reconstruct inclined cosmic-ray air showers
with zenith angles greater than detected with the surface array of
the Pierre Auger Observatory. The measured signals at the ground level are
fitted to muon density distributions predicted with atmospheric cascade models
to obtain the relative shower size as an overall normalization parameter. The
method is evaluated using simulated showers to test its performance. The energy
of the cosmic rays is calibrated using a sub-sample of events reconstructed
with both the fluorescence and surface array techniques. The reconstruction
method described here provides the basis of complementary analyses including an
independent measurement of the energy spectrum of ultra-high energy cosmic rays
using very inclined events collected by the Pierre Auger Observatory.Comment: 27 pages, 19 figures, accepted for publication in Journal of
Cosmology and Astroparticle Physics (JCAP
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