M. Kachelriess

NTNU Samfunnsforskning, Nidaros, Sør-Trøndelag, Norway

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Publications (102)229.87 Total impact

  • M. Kachelriess, S. Ostapchenko
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    ABSTRACT: We calculate the neutrino yield from collisions of cosmic ray (CR) nuclei on gas using the event generator QGSJET-II. We present first the general characteristics and numerical results for the neutrino yield assuming power-law fluxes for the primary CR nuclei. Then we use three parameterisations for the Galactic CR flux to derive the neutrino yield for energies around and above the knee. The shape and the normalization of the resulting neutrino fluxes above $\sim 10^{14}$ eV depend strongly on the composition of the Galactic CR flux employed, but is generally dominated by its proton component. The spectral shape and magnitude of the neutrino flux suggest that the IceCube excess is connected to CR overdensities around recent close-by Galactic sources, if the events have a Galactic origin.
    05/2014;
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    G. Giacinti, M. Kachelriess, D. V. Semikoz
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    ABSTRACT: We study the escape of cosmic rays (CRs) with energies between $E/Z=10^{14}$ eV and $10^{17}$ eV from our Galaxy, calculating the trajectories of individual CRs in recent models of the regular and turbulent Galactic magnetic field. Determining the average grammage $X(E)$ traversed by CRs, we find a knee-like structure of $X(E)$ around $E/Z=$ few $\times 10^{15}$ eV for a coherence length $l_{\rm c} \simeq 5$ pc of the turbulent field. The resulting change in the slope of $X(E)$ is sufficiently strong to explain the proton knee observed by KASCADE: Thus the knee may, in this regard, be entirely explained by CR leakage from the Milky Way, rendering additional effects unnecessary. We find that the decrease of $X(E)$ slows down around $E/Z \simeq 10^{16}$ eV in a model with a weak turbulent magnetic field, in agreement with the energy dependence of the proton flux as determined by KASCADE-Grande.
    03/2014;
  • G. Giacinti, M. Kachelriess, D. V. Semikoz
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    ABSTRACT: Analyses of TeV-PeV cosmic ray (CR) diffusion around their sources usually assume either isotropic diffusion or anisotropic diffusion due to the regular Galactic magnetic field. We show that none of them are adequate on distances smaller than the maximal scale Lmax ~ 100 pc of fluctuations in the turbulent interstellar magnetic field. As a result, we predict anisotropic gamma-ray emissions around CR proton and electron sources, even for uniform densities of target gas. The centers of extended emission regions may have non-negligible offsets from their sources, leading to risks of misidentification. Gamma-rays from CR filaments have steeper energy spectra than those from surrounding regions. We point out that gamma-ray telescopes can be used in the future as a new way to probe and deduce the parameters of the interstellar magnetic field.
    Physical review D: Particles and fields 06/2013; 88(2).
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    ABSTRACT: In this work, we investigate the impacts a potential shift towards a heavy composition at the end of the cosmic ray (CR) spectrum would have on the future data [1, 2]. We present detailed simulations for the propagation of ultra-high energy (UHE) heavy nuclei, with E ≥ 60 EeV, within recent Galactic magnetic field (GMF) models. We consider both regular and turbulent components of the GMF. We show that with UHE heavy nuclei, there is no one-to-one correspondence between the arrival directions of cosmic rays measured at Earth and the direction of their extragalactic sources. Sources can have several distorted images on the sky. We compute images of galaxy clusters and of the supergalactic plane in recent GMF models and show the challenges, but also the possibilities, of "ultra-high energy cosmic ray astronomy" with heavy nuclei. Finally, we present a quantitative study of the impact of the GMF on the (de-)magnification of source fluxes, due to magnetic lensing. Such effects cannot be neglected in case of heavy primaries.
    06/2013;
  • G. Giacinti, M. Kachelrieß, D. V. Semikoz, G. Sigl
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    ABSTRACT: This talk based on results of ref. [1], where we constrain the energy at which the transition from Galactic to extragalactic cosmic rays occurs by computing the anisotropy at Earth of cosmic rays emitted by Galactic sources. Since the diffusion approximation starts to loose its validity for E/Z ≳ 10(16-17) eV, we propagate individual cosmic rays using Galactic magnetic field models and taking into account both their regular and turbulent components. The turbulent field is generated on a nested grid which allows spatial resolution down to fractions of a parsec. If the primary composition is mostly light or intermediate around E ˜ 1018 eV, the transition at the ankle is ruled out, except in the unlikely case of an extreme Galactic magnetic field with strength >10 μG. Therefore, the fast rising proton contribution suggested by KASCADE-Grande data between 1017 eV and 1018 eV should be of extragalactic origin. In case heavy nuclei dominate the flux at E > 1018 eV, the transition energy can be close to the ankle, if Galactic cosmic rays are produced by sufficiently frequent transients as e.g. magnetars.
    06/2013;
  • M. Kachelrieß
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    ABSTRACT: High-energy neutrino astronomy has grown up, with IceCube as one of its main experiments having sufficient sensitivity to test “vanilla” models of astrophysical neutrinos. I review predictions of neutrino fluxes as well as the status of cosmic ray physics. I comment also briefly on an improvement of the Fermi-LAT limit for cosmogenic neutrinos and on the two neutrino events presented by IceCube first at “Neutrino 2012”.
    Nuclear Physics B - Proceedings Supplements 04/2013; s 237–238:218–223. · 0.88 Impact Factor
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    M. Kachelriess, S. Ostapchenko
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    ABSTRACT: We calculate the diffuse intensity of cosmic ray (CR) nuclei and their secondaries in the Boron-Carbon group produced by supernova remnants (SNR). The trajectories of charged particles in the SNR are modeled as a random walk in the test particle approximation. Secondary production by CRs colliding with gas in the SNR is included as a Monte Carlo process, while we use Galprop to account for the propagation and interactions of CRs in the Galaxy. In the vicinity of a source, we find an approximately constant B/C ratio as a function of energy. As a result, the B/C ratio at Earth does not rise with energy, but flattens instead in the high energy limit. This prediction can be soon tested by the AMS-2 collaboration.
    Physical review D: Particles and fields 11/2012; 87(4).
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    L. A. Dal, M. Kachelriess
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    ABSTRACT: We calculate the antideuteron yield in dark matter annihilations on an event-by-event basis using the HERWIG++ Monte Carlo generator. We present the resulting antideuteron fluxes for quark and gauge boson final states. As deuteron production in the coalescence model depends on momentum differences between nucleons that are small compared to \Lambda_{QCD}, it is potentially very sensitive to the hadronization model employed. We therefore compare our antideuteron yields to earlier results based on PYTHIA, thereby estimating their uncertainties. We also briefly discuss the importance of n>2 final states for annihilations of heavy DM particles.
    Physical review D: Particles and fields 07/2012; 86(10).
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    M. Kachelriess, S. Ostapchenko
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    ABSTRACT: A fundamental problem of cosmic ray (CR) physics is the determination of the average properties of Galactic CRs outside the Solar system. Starting from COS-B data in the 1980's, gamma-ray observations of molecular clouds in the Gould Belt above the Galactic plane have been used to deduce the Galactic CR energy spectrum. We reconsider this problem in view of the improved precision of observational data which in turn require a more precise treatment of photon production in proton-proton scatterings. We show that the spectral shape $dN/dp\propto p^{-2.85}$ of CR protons as determined by the PAMELA collaboration in the energy range 80 GeV<pc<230 GeV is consistent with the photon spectra from molecular clouds observed with Fermi-LAT down to photon energies E\sim 1-2 GeV. Adding a break of the CR flux at 3 GeV, caused by a corresponding change of the diffusion coefficient, improves further the agreement in the energy range 0.2-3 GeV.
    Physical review D: Particles and fields 06/2012; 86(4).
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    G. Giacinti, M. Kachelriess, D. V. Semikoz
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    ABSTRACT: We investigate the diffusion of cosmic rays (CR) close to their sources. Propagating individual CRs in purely isotropic turbulent magnetic fields with maximal scale of spatial variations Lmax, we find that CRs diffuse anisotropically at distances r <~ Lmax from their sources. As a result, the CR densities around the sources are strongly irregular and show filamentary structures. We determine the transition time t* to standard diffusion as t* ~ 10^4 yr (Lmax/150 pc)^b (E/PeV)^(-g) (Brms/4 muG)^g, with b ~ 2 and g = 0.25-0.5 for a turbulent field with Kolmogorov power spectrum. We calculate the photon emission due to CR interactions with gas and the resulting irregular source images.
    Physical Review Letters 04/2012; 108(26). · 7.73 Impact Factor
  • M Kachelrieß, S Ostapchenko, R Tomàs
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    ABSTRACT: We discuss different approaches to infer the properties of the intergalactic magnetic field (IGMF) from gamma-ray observations of blazars. In particular, we investigate constraints on the IGMF strength and spacial distribution, resulting from studies of TeV blazars by imaging atmospheric Cherenkov telescopes and the Fermi-LAT instrument. We demonstrate that the non-observation of GeV gamma-rays from powerful TeV blazars indicates that more than 60% of space is filled by magnetic fields with stength ≳ 10−15 G, favoring the primordial IGMF origin.
    Journal of Physics Conference Series 01/2012; 375(5).
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    ABSTRACT: We describe some specific but reasonable conditions for the formation of superdense clumps (or minihalos) of dark matter. Such clumps can be produced by several mechanisms, most notably by spiky features in the spectrum of density perturbations. Being produced very early during the radiation-dominated epoch, these clumps evolve as isolated objects. They do not belong to hierarchical structures for a long time after production and are therefore not destroyed by tidal interactions during the formation of larger structures. If the clumps are constituted of superheavy dark matter particles, then the evolution of their central part can lead to a “gravithermal catastrophe,” increasing the central density and thus the annihilation signal. As a result, annihilations of superheavy neutralinos in dense clumps may lead to observable fluxes of annihilation products in the form of ultrahigh-energy particles.
    Theoretical and Mathematical Physics 01/2012; 170(1). · 0.67 Impact Factor
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    G. Giacinti, M. Kachelriess, D. V. Semikoz, G. Sigl
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    ABSTRACT: We constrain the energy at which the transition from Galactic to extragalactic cosmic rays occurs by computing the anisotropy at Earth of cosmic rays emitted by Galactic sources. Since the diffusion approximation starts to loose its validity for E/Z >~ 10^(16-17) eV, we propagate individual cosmic rays (CRs) using Galactic magnetic field models and taking into account both their regular and turbulent components. The turbulent field is generated on a nested grid which allows spatial resolution down to fractions of a parsec. Assuming sufficiently frequent Galactic CR sources, the dipole amplitude computed for a mostly light or intermediate primary composition exceeds the dipole bounds measured by the Auger collaboration around E ~ 10^18 eV. Therefore, a transition at the ankle or above would require a heavy composition or a rather extreme Galactic magnetic field with strength >~ 10 muG. Moreover, the fast rising proton contribution suggested by KASCADE-Grande data between 10^17 eV and 10^18 eV should be of extragalactic origin. In case heavy nuclei dominate the flux at E >~ 10^18 eV, the transition energy can be close to the ankle, if Galactic CRs are produced by sufficiently frequent transients as e.g. magnetars.
    Journal of Cosmology and Astroparticle Physics 12/2011; 2012(07). · 6.04 Impact Factor
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    G. Giacinti, M. Kachelriess, D. V. Semikoz, G. Sigl
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    ABSTRACT: In this work, we present detailed simulations for propagation of ultra-high energy (UHE) heavy nuclei, with E > 60 EeV, within recent Galactic Magnetic Field (GMF) models. We investigate the impacts of the regular and turbulent components of the GMF. We show that with UHE heavy nuclei, there is no one-to-one correspondence between the arrival directions of cosmic rays (CR) measured at Earth and the direction of their extragalactic sources. Sources can have several distorted images on the sky. We compute images of galaxy clusters and of the supergalactic plane in recent GMF models and show the challenges, and possibilities, of "UHECR astronomy" with heavy nuclei. Finally, we present a quantitative study of the impact of the GMF on the (de-)magnification of source fluxes, due to magnetic lensing effects. We find that for 60 EeV iron nuclei, sources located in up to about one fifth of the sky would have their fluxes so strongly demagnified that they would not be detectable at Earth, even by the next generation of UHECR experiments.
    08/2011;
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    M. Kachelriess, S. Ostapchenko, R. Tomas
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    ABSTRACT: A Monte Carlo program for the simulation of electromagnetic cascades initiated by high-energy photons and electrons interacting with extragalactic background light (EBL) is presented. Pair production and inverse Compton scattering on EBL photons as well as synchrotron losses and deflections of the charged component in extragalactic magnetic fields (EGMF) are included in the simulation. Weighted sampling of the cascade development is applied to reduce the number of secondary particles and to speed up computations. As final result, the simulation procedure provides the energy, the observation angle, and the time delay of secondary cascade particles at the present epoch. Possible applications are the study of TeV blazars and the influence of the EGMF on their spectra or the calculation of the contribution from ultrahigh energy cosmic rays or dark matter to the diffuse extragalactic gamma-ray background. As an illustration, we present results for deflections and time-delays relevant for the derivation of limits on the EGMF.
    Computer Physics Communications 06/2011; · 2.41 Impact Factor
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    G. Giacinti, M. Kachelriess, D. V. Semikoz, G. Sigl
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    ABSTRACT: In this work we study how the turbulent component of the Galactic magnetic field (GMF) affects the propagation of ultrahigh energy heavy nuclei. We investigate first how the images of individual sources and of the supergalactic plane depend on the properties of the turbulent GMF. Then we present a quantitative study of the impact of the turbulent field on (de-) magnification of source fluxes, due to magnetic lensing effects. We also show that it is impossible to explain the Pierre Auger data assuming that all ultrahigh energy nuclei are coming from Cen A, even in the most favorable case of a strong, extended turbulent field in the Galactic halo.
    Astroparticle Physics 04/2011; 35(4). · 4.78 Impact Factor
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    M. Kachelriess, S. Ostapchenko, R. Tomas
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    ABSTRACT: We calculate the energy spectra of cosmic rays (CR) and their secondaries produced in a supernova remnant (SNR), taking into account the time-dependence of the SNR shock. We model the trajectories of charged particles as a random walk with a prescribed diffusion coefficient, accelerating the particles at each shock crossing. Secondary production by CRs colliding with gas is included as a Monte Carlo process. We find that SNRs produce less antimatter than suggested previously: The positron/electron ratio and the antiproton/proton ratio are a few percent and few $\times 10^{-5}$, respectively. Moreover, the obtained positron/electron ratio decreases with energy, while the antiproton/proton ratio rises at most by a factor of two above 10 GeV.
    The Astrophysical Journal 03/2011; 733(2). · 6.73 Impact Factor
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    ABSTRACT: Ultrahigh energy cosmic ray (UHECR) protons interacting with the cosmic microwave background (CMB) produce UHE electrons and gamma-rays that in turn initiate electromagnetic cascades on CMB and infrared photons. As a result, a background of diffuse isotropic gamma-radiation is accumulated in the energy range E≲100 GeV. The Fermi-LAT Collaboration has recently reported a measurement of the extragalactic diffuse background finding it less intense and softer than previously measured by EGRET. We show that this new result constrains UHECR models and the flux of cosmogenic neutrinos. In particular, it excludes models with cosmogenic neutrino fluxes detectable by existing neutrino experiments, while next-generation detectors as e.g. JEM-EUSO can observe neutrinos only for extreme parameters.
    Physics Letters B 01/2011; · 4.57 Impact Factor
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    K. Dolag, M. Kachelriess, S. Ostapchenko, R. Tomas
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    ABSTRACT: High energy photons from blazars can initiate electromagnetic pair cascades interacting with the extragalactic photon background. The charged component of such cascades is deflected and delayed by extragalactic magnetic fields (EGMF), reducing thereby the observed point-like flux and leading potentially to multi degree images in the GeV energy range. We calculate the fluence of 1ES 0229+200 as seen by Fermi-LAT for different EGMF profiles using a Monte Carlo simulation for the cascade development. The non-observation of 1ES 0229+200 by Fermi-LAT suggests that the EGMF fills at least 60% of space with fields stronger than {\cal O}(10^{-16}-10^{-15})G for life times of TeV activity of {\cal O}(10^2-10^4)yr. Thus the (non-) observation of GeV extensions around TeV blazars probes the EGMF in voids and puts strong constraints on the origin of EGMFs: Either EGMFs were generated in a space filling manner (e.g. primordially) or EGMFs produced locally (e.g. by galaxies) have to be efficiently transported to fill a significant volume fraction, as e.g. by galactic outflows. Comment: 5 pages, 5 eps figures; v2: added discussion of time delays
    The Astrophysical Journal 09/2010; · 6.73 Impact Factor
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    G. Giacinti, M. Kachelriess, D. V. Semikoz, G. Sigl
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    ABSTRACT: Observations are consistent with a significant fraction of heavy nuclei in the cosmic ray flux above a few times 10^19 eV. Such nuclei can be deflected considerably in the Galactic magnetic field, with important implications for the search of their sources. We perform detailed simulations of heavy nuclei propagation within recent Galactic magnetic field models. While such models are not yet sufficiently constrained to predict deflection maps in detail, we find general features of the distribution of (de-) magnified flux from sources. Since in most theoretical models sources of heavy nuclei are located in the local large scale structure of galaxies, we show examples of images of several nearby galaxy clusters and of the supergalactic plane. Such general features may be useful to develop efficient methods for source reconstruction from observed ultrahigh energy cosmic ray arrival directions. Comment: 17 pages, 11 figures. Published in JCAP
    Journal of Cosmology and Astroparticle Physics 06/2010; · 6.04 Impact Factor

Publication Stats

2k Citations
229.87 Total Impact Points

Institutions

  • 2006–2013
    • NTNU Samfunnsforskning
      Nidaros, Sør-Trøndelag, Norway
  • 2005–2013
    • Teknologisk Institutt Norway
      Kristiania (historical), Oslo County, Norway
    • Collège de France
      Lutetia Parisorum, Île-de-France, France
  • 2012
    • Norwegian University of Science and Technology
      Nidaros, Sør-Trøndelag, Norway
  • 2009
    • University of Hamburg
      • II. Institut für Theoretische Physik
      Hamburg, Hamburg, Germany
  • 2002–2006
    • Max Planck Institute of Physics
      München, Bavaria, Germany
  • 2000–2002
    • CERN
      • Physics Department (PH)
      Genève, Geneva, Switzerland
  • 1995–1998
    • Ruhr-Universität Bochum
      Bochum, North Rhine-Westphalia, Germany