M. Kachelriess

NTNU Samfunnsforskning, Nidaros, Sør-Trøndelag, Norway

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Publications (114)361.17 Total impact

  • V. Savchenko, M. Kachelriess, D. V. Semikoz
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    ABSTRACT: We study numerically the anisotropy of the cosmic ray (CR) flux emitted by a single source calculating the trajectories of individual CRs. We show that the contribution of a single source to the observed anisotropy is instead determined solely by the fraction the source contributes to the total CR intensity, its age and its distance,and does not depend on the CR energy at late times. Therefore the observation of a constant dipole anisotropy indicates that a single source dominates the CR flux in the corresponding energy range. A natural explanation for the plateau between 2--20 TeV observed in the CR anisotropy is thus the presence of a single, nearby source. For the source age of 2 Myr, as suggested by the explanation of the antiproton and positron data from PAMELA and AMS-02 through a local source [arXiv:astro-ph/1504.06472], we determine the source distance as $\sim 200$ pc. Combined with the contribution of the global CR sea calculated in the escape model, we can explain qualitatively the data for the dipole anisotropy. Our results suggest that the assumption of a smooth CR source distribution should be abandoned between 200 GeV and 1 PeV.
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    M. Kachelriess, A. Neronov, D. V. Semikoz
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    ABSTRACT: The locally observed cosmic ray spectrum has several puzzling features, such as the excess of positrons and antiprotons above $\sim 20$ GeV and the discrepancy in the slopes of the spectra of cosmic ray protons and heavier nuclei in the TeV-PeV energy range. We show that these features are consistently explained by a nearby source which was active $\sim 2$ Myr ago and has injected $(1-2)\times 10^{50}$ erg in cosmic rays. The transient nature of the source and its overall energy budget point to the supernova origin of this local cosmic ray source. The age of the supernova suggests that the local cosmic ray injection was produced by the same supernova that has deposited $^{60}$Fe isotopes in the deep ocean crust.
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    ABSTRACT: A dramatic increase in the accuracy and statistics of space-borne cosmic ray (CR) measurements has yielded several breakthroughs over the last several years. The most puzzling is the rise in the positron fraction above ~10 GeV over the predictions of the propagation models assuming pure secondary production. The accuracy of the antiproton production cross section is critical for astrophysical applications and searches for new physics since antiprotons in CRs seem to hold the keys to many puzzles including the origin of those excess positrons. However, model calculations of antiproton production in CR interactions with interstellar gas are often employing parameterizations that are out of date or are using outdated physical concepts. That may lead to an incorrect interpretation of antiproton data which could have broad consequences for other areas of astrophysics. In this work, we calculate antiproton production in pp-, pA-, and AA-interactions using EPOS-LHC and QGSJET-II-04, two of the most advanced Monte Carlo (MC) generators tuned to numerous accelerator data including those from the Large Hadron Collider (LHC). We show that the antiproton yields obtained with these MC generators differ by up to an order of magnitude from yields of parameterizations commonly used in astrophysics.
    The Astrophysical Journal 02/2015; 803(2). DOI:10.1088/0004-637X/803/2/54 · 6.28 Impact Factor
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    G. Giacinti, M. Kachelriess, D. V. Semikoz
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    ABSTRACT: We show that the cosmic ray (CR) knee can be entirely explained by energy-dependent CR leakage from the Milky Way, with an excellent fit to all existing data. We test this hypothesis calculating the trajectories of individual CRs in the Galactic magnetic field. We find that the CR escape time $\tau_{\rm esc}(E)$ exhibits a knee-like structure around $E/Z={\rm few}\times 10^{15}$ eV for small coherence lengths and strengths of the turbulent magnetic field. The resulting intensities for different groups of nuclei are consistent with the ones determined by KASCADE and KASCADE-Grande, using simple power-laws as injection spectra. The transition from Galactic to extragalactic CRs is terminated at $\approx 2\times 10^{18}$ eV, while extragalactic CRs contribute sizeable to the subdominant proton flux already for $\gtrsim 2\times 10^{16}$ eV. The natural source of extragalactic CRs in the intermediate energy region up to the ankle are in this model normal and starburst galaxies. The escape model provides a good fit to $\ln(A)$ data; it predicts that the phase of the CR dipole varies strongly in the energy range between $1\times 10^{17}$ and $3\times 10^{18}$ eV, while our estimate for the dipole magnitude is consistent with observations.
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    ABSTRACT: The concept of the nuclear enhancement factor has been used since the beginning of gamma-ray astronomy. It provides a simple and convenient way to account for the contribution of nuclei (A>1) in cosmic rays (CRs) and in the interstellar medium (ISM) to the diffuse gamma-ray emission. An accurate treatment of the dominant emission process, such as hadronic interactions of CRs with the ISM, enables one to study CR acceleration processes, CR propagation in the ISM, and provides a reliable background model for searches of new phenomena. The Fermi Large Area Telescope (Fermi-LAT) launched in 2008 provides excellent quality data in a wide energy range 30 MeV - 1 TeV where the diffuse emission accounts for the majority of photons. Exploiting its data to the fullest requires a new study of the processes of gamma-ray production in hadronic interactions. In this paper we point out that several commonly used studies of the nuclear enhancement factor miss to account for the spectrally averaged energy loss fraction which ensures that the energy fraction transferred to photons is averaged properly with the spectra of CR species. We present a new calculation of the spectrally averaged energy loss fraction and the nuclear enhancement factor using the QGSJET-II-04 and EPOS-LHC interaction models.
    The Astrophysical Journal 05/2014; 789(2). DOI:10.1088/0004-637X/789/2/136 · 6.28 Impact Factor
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    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.
    Physical Review D 05/2014; 90(8). DOI:10.1103/PhysRevD.90.083002 · 4.86 Impact Factor
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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.
    Physical Review D 03/2014; 90(4). DOI:10.1103/PhysRevD.90.041302 · 4.86 Impact Factor
  • 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). DOI:10.1103/PhysRevD.88.023010 · 4.86 Impact Factor
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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.
    The European Physical Journal Conferences 06/2013; 53:06004-. DOI:10.1051/epjconf/20135306004
  • 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.
    The European Physical Journal Conferences 06/2013; 53:06002-. DOI:10.1051/epjconf/20135306002
  • 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. DOI:10.1016/j.nuclphysbps.2013.04.093 · 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). DOI:10.1103/PhysRevD.87.047301 · 4.86 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 07/2012; 375(5). DOI:10.1088/1742-6596/375/1/052030
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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). DOI:10.1103/PhysRevD.86.103536 · 4.86 Impact Factor
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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). DOI:10.1103/PhysRevD.86.043004 · 4.86 Impact Factor
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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). DOI:10.1103/PhysRevLett.108.261101 · 7.73 Impact Factor
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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.
    01/2012; 170(1):102-109. DOI:10.4213/tmf6748
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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). DOI:10.1007/s11232-012-0008-7 · 0.70 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). DOI:10.1088/1475-7516/2012/07/031 · 5.88 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.

Publication Stats

2k Citations
361.17 Total Impact Points

Institutions

  • 2007–2015
    • NTNU Samfunnsforskning
      Nidaros, Sør-Trøndelag, Norway
  • 2006–2012
    • Norwegian University of Science and Technology
      Nidaros, Sør-Trøndelag, Norway
  • 2005–2010
    • Teknologisk Institutt Norway
      Kristiania (historical), Oslo County, Norway
  • 2008
    • Joint Institute for Nuclear Research
      Dubno, Moskovskaya, Russia
  • 2002–2005
    • Max Planck Institute of Physics
      München, Bavaria, Germany
  • 2000–2002
    • CERN
      • Physics Department (PH)
      Genève, Geneva, Switzerland
  • 1999
    • Tufts University
      • Tufts Institute of Cosmology
      Бостон, Georgia, United States
  • 1995–1998
    • INFN - Istituto Nazionale di Fisica Nucleare
      Frascati, Latium, Italy
  • 1995–1997
    • Ruhr-Universität Bochum
      • Institut für Theoretische Physik I
      Bochum, North Rhine-Westphalia, Germany