On the knee in the energy spectrum of cosmic rays
TL;DR: In this article, direct and indirect measurements of cosmic rays are reviewed, with emphasis given to the understanding of the knee in the energy spectrum, and the data are compared to contemporary models for the knee.
About: This article is published in Astroparticle Physics.The article was published on 2003-05-01 and is currently open access. It has received 414 citations till now. The article focuses on the topics: Cosmic-ray observatory & Cosmic ray.
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TL;DR: The ALICE Collaboration as mentioned in this paper is a general-purpose heavy-ion experiment designed to study the physics of strongly interacting matter and the quark-gluon plasma in nucleus-nucleus collisions at the LHC.
Abstract: ALICE is a general-purpose heavy-ion experiment designed to study the physics of strongly interacting matter and the quark–gluon plasma in nucleus–nucleus collisions at the LHC. It currently involves more than 900 physicists and senior engineers, from both the nuclear and high-energy physics sectors, from over 90 institutions in about 30 countries.The ALICE detector is designed to cope with the highest particle multiplicities above those anticipated for Pb–Pb collisions (dNch/dy up to 8000) and it will be operational at the start-up of the LHC. In addition to heavy systems, the ALICE Collaboration will study collisions of lower-mass ions, which are a means of varying the energy density, and protons (both pp and pA), which primarily provide reference data for the nucleus–nucleus collisions. In addition, the pp data will allow for a number of genuine pp physics studies.The detailed design of the different detector systems has been laid down in a number of Technical Design Reports issued between mid-1998 and the end of 2004. The experiment is currently under construction and will be ready for data taking with both proton and heavy-ion beams at the start-up of the LHC.Since the comprehensive information on detector and physics performance was last published in the ALICE Technical Proposal in 1996, the detector, as well as simulation, reconstruction and analysis software have undergone significant development. The Physics Performance Report (PPR) provides an updated and comprehensive summary of the performance of the various ALICE subsystems, including updates to the Technical Design Reports, as appropriate.The PPR is divided into two volumes. Volume I, published in 2004 (CERN/LHCC 2003-049, ALICE Collaboration 2004 J. Phys. G: Nucl. Part. Phys. 30 1517–1763), contains in four chapters a short theoretical overview and an extensive reference list concerning the physics topics of interest to ALICE, the experimental conditions at the LHC, a short summary and update of the subsystem designs, and a description of the offline framework and Monte Carlo event generators.The present volume, Volume II, contains the majority of the information relevant to the physics performance in proton–proton, proton–nucleus, and nucleus–nucleus collisions. Following an introductory overview, Chapter 5 describes the combined detector performance and the event reconstruction procedures, based on detailed simulations of the individual subsystems. Chapter 6 describes the analysis and physics reach for a representative sample of physics observables, from global event characteristics to hard processes.
587 citations
TL;DR: In this paper, an isotropic, unbroken power-law flux with a normalization at 100 TeV neutrino energy of (0.90 -0.27 +0.30) × 10-18 Gev-1 cm-2 s-1 sr-1 and a hard spectral index of γ = 2.13 ± 0.13.
Abstract: The IceCube Collaboration has previously discovered a high-energy astrophysical neutrino flux using neutrino events with interaction vertices contained within the instrumented volume of the IceCube detector. We present a complementary measurement using charged current muon neutrino events where the interaction vertex can be outside this volume. As a consequence of the large muon range the effective area is significantly larger but the field of view is restricted to the Northern Hemisphere. IceCube data from 2009 through 2015 have been analyzed using a likelihood approach based on the reconstructed muon energy and zenith angle. At the highest neutrino energies between 194 TeV and 7.8 PeV a significant astrophysical contribution is observed, excluding a purely atmospheric origin of these events at 5.6s significance. The data are well described by an isotropic, unbroken power-law flux with a normalization at 100 TeV neutrino energy of (0.90 -0.27 +0.30) × 10-18 Gev-1 cm-2 s-1 sr-1and a hard spectral index of γ = 2.13 ± 0.13. The observed spectrum is harder in comparison to previous IceCube analyses with lower energy thresholds which may indicate a break in the astrophysical neutrino spectrum of unknown origin. The highest-energy event observed has a reconstructed muon energy of (4.5 ± 1.2) PeV which implies a probability of less than 0.005% for this event to be of atmospheric origin. Analyzing the arrival directions of all events with reconstructed muon energies above 200 TeV no correlation with known γ-ray sources was found. Using the high statistics of atmospheric neutrinos we report the current best constraints on a prompt atmospheric muon neutrino flux originating from charmed meson decays which is below 1.06 in units of the flux normalization of the model in Enberg et al.
503 citations
TL;DR: In this article, the spectral features of extragalactic protons interacting with the cosmic microwave background (CMB) are calculated in a model-independent way using the power-law generation spectrum.
Abstract: We argue that an astrophysical solution to the ultrahigh energy cosmic ray (UHECR) problem is viable. The detailed study of UHECR energy spectra is performed. The spectral features of extragalactic protons interacting with the cosmic microwave background (CMB) are calculated in a model-independent way. Using the power-law generation spectrum $\ensuremath{\propto}{E}^{\ensuremath{-}{\ensuremath{\gamma}}_{g}}$ as the only assumption, we analyze four features of the proton spectrum: the GZK cutoff, dip, bump, and the second dip. We found the dip, induced by electron-positron production on the CMB, to be the most robust feature, existing in energy range $1\ifmmode\times\else\texttimes\fi{}{10}^{18}\char21{}4\ifmmode\times\else\texttimes\fi{}{10}^{19}\text{ }\text{ }\mathrm{eV}$. Its shape is stable relative to various phenomena included in calculations: discreteness of the source distribution, different modes of UHE proton propagation (from rectilinear to diffusive), local overdensity or deficit of the sources, large-scale inhomogeneities in the universe, and interaction fluctuations. The dip is well confirmed by observations of the AGASA, HiRes, Fly's Eye, and Yakutsk detectors. With two free parameters (${\ensuremath{\gamma}}_{g}$ and flux normalization constant) the dip describes about 20 energy bins with ${\ensuremath{\chi}}^{2}/\mathrm{d}.\mathrm{o}.\mathrm{f}.\ensuremath{\approx}1$ for each experiment. The best fit is reached at ${\ensuremath{\gamma}}_{g}=2.7$, with the allowed range 2.55\char21{}2.75. The dip is used for energy calibration of the detectors. For each detector independently, the energy is shifted by factor $\ensuremath{\lambda}$ to reach the minimum ${\ensuremath{\chi}}^{2}$. We found ${\ensuremath{\lambda}}_{\mathrm{Ag}}=0.9$, ${\ensuremath{\lambda}}_{\mathrm{Hi}}=1.2$, and ${\ensuremath{\lambda}}_{\mathrm{Ya}}=0.75$ for the AGASA, HiRes, and Yakutsk detectors, respectively. Remarkably, after this energy shift the fluxes and spectra of all three detectors agree perfectly, with discrepancy between AGASA and HiRes at $Eg1\ifmmode\times\else\texttimes\fi{}{10}^{20}\text{ }\text{ }\mathrm{eV}$ being not statistically significant. The excellent agreement of the dip with observations should be considered as confirmation of UHE proton interaction with the CMB. The dip has two flattenings. The high energy flattening at $E\ensuremath{\approx}1\ifmmode\times\else\texttimes\fi{}{10}^{19}\text{ }\text{ }\mathrm{eV}$ automatically explains ankle, the feature observed in all experiments starting from the 1980s. The low-energy flattening at $E\ensuremath{\approx}1\ifmmode\times\else\texttimes\fi{}{10}^{18}\text{ }\text{ }\mathrm{eV}$ reproduces the transition to galactic cosmic rays. This transition is studied quantitatively in this work. Inclusion of primary nuclei with a fraction of more than 20% upsets the agreement of the dip with observations, which we interpret as an indication of the acceleration mechanism. We study in detail the formal problems of spectra calculations: energy losses (the new detailed calculations are presented), the analytic method of spectrum calculations, and the study of fluctuations with the help of a kinetic equation. The UHECR sources, AGN and GRBs, are studied in a model-dependent way, and acceleration is discussed. Based on the agreement of the dip with existing data, we make the robust prediction for the spectrum at $1\ifmmode\times\else\texttimes\fi{}{10}^{18}\char21{}1\ifmmode\times\else\texttimes\fi{}{10}^{20}\text{ }\text{ }\mathrm{eV}$ to be measured in the nearest future by the Auger detector. We also predict the spectral signature of nearby sources, if they are observed by Auger. This paper is long and contains many technical details. For those who are interested only in physical content we recommend the Introduction and Conclusions, which are written as autonomous parts of the paper.
483 citations
TL;DR: In this article, a review of high-energy neutrinos (E ν > 100 GeV ) with the main topics as follows are: • The production mechanism of high energy neutrino in astrophysical shocks.
307 citations
TL;DR: In this paper, a review summarizes recent developments in the understanding of high-energy cosmic rays focusing on galactic and presumably extragalactic particles in the energy range from the knee (1015 eV ) up to the highest energies observed ( > 10 20 eV).
300 citations
References
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TL;DR: In this article, the central idea of diffusive shock acceleration is presented from microscopic and macroscopic viewpoints; applied to reactionless test particles in a steady plane shock, the mechanism is shown to produce a power law spectrum in momentum with a slope which, to lowest order in the ratio of plasma to particle speed, depends only on the compression in the shock.
Abstract: The central idea of diffusive shock acceleration is presented from microscopic and macroscopic viewpoints; applied to reactionless test particles in a steady plane shock the mechanism is shown to produce a power law spectrum in momentum with a slope which, to lowest order in the ratio of plasma to particle speed, depends only on the compression in the shock. The associated time scale is found (also by a macroscopic and a microscopic method) and the problems of spherical shocks, as exemplified by a point explosion and a stellar-wind terminator, are treated by singular perturbation theory. The effect of including the particle reaction is then studied. It is shown that if the scattering is due to resonant waves these can rapidly grow with unknown consequences. The possible steady modified shock structures are classified and generalised Rankine-Hugoniot conditions found. Modifications of the spectrum are discussed on the basis of an exact, if rather artificial, solution, a high-energy asymptotic expansion and a perturbation expansion due to Blandford. It is pointed out that no steady solution can exist for very strong shocks; the possible time dependence is briefly discussed.
1,616 citations
TL;DR: In this paper, a method for the numerical computation of the propagation of primary and secondary nucleons, primary electrons, and secondary positrons and electrons is described, and the height of the halo propagation region is determined using recent 10Be/9Be measurements.
Abstract: We describe a method for the numerical computation of the propagation of primary and secondary nucleons, primary electrons, and secondary positrons and electrons. Fragmentation and energy losses are computed using realistic distributions for the interstellar gas and radiation fields, and diffusive reacceleration is also incorporated. The models are adjusted to agree with the observed cosmic-ray B/C and 10Be/9Be ratios. Models with diffusion and convection do not account well for the observed energy dependence of B/C, while models with reacceleration reproduce this easily. The height of the halo propagation region is determined using recent 10Be/9Be measurements as >4 kpc for diffusion/convection models and 4-12 kpc for reacceleration models. For convection models, we set an upper limit on the velocity gradient of dV/dz < 7 km s-1 kpc-1. The radial distribution of cosmic-ray sources required is broader than current estimates of the supernova remnant (SNR) distribution for all halo sizes. Full details of the numerical method used to solve the cosmic-ray propagation equation are given.
1,048 citations
TL;DR: The present status of abundance information for elements in meteorites and in the Sun is reviewed, and a new table of abundances of the elements, which should be characteristic of the primitive solar nebula, is compiled and presented.
Abstract: The present status of abundance information for elements in meteorites and in the Sun is reviewed, and a new table of abundances of the elements, which should be characteristic of the primitive solar nebula, is compiled and presented. Special attention is called to the elemental abundances in the silicon-to-calcium region, where many of the abundances are rather poorly determined, and where these abundances have an impact on theories of nucleosynthesis of the elements. To each elemental isotope is assigned a mechanism of nucleosynthesis which may have been responsible for production of most of that isotope, and brief comments are made concerning the present status of understanding of the different mechanisms of nucleosynthesis.
825 citations
TL;DR: A review of the history of research in this energy regime and critical assessment of the observational results on the energy spectrum, arrival directions, and composition of the primary cosmic rays based on observations made by six experiments is given in this paper.
Abstract: The authors define ``ultrahigh-energy cosmic rays'' (UHECRs) as those cosmic rays with energies above ${10}^{18}\mathrm{eV}.$ It had been anticipated that there would be a cutoff in the energy spectrum of primary cosmic rays around $6\ifmmode\times\else\texttimes\fi{}{10}^{19}\mathrm{eV}$ induced by the interaction of the particles with the 2.7-K primordial photons. However, recent experimental data have established that particles exist with energies greatly exceeding this. It follows that the sources of such particles are probably nearby, on a cosmological scale. However, although the trajectories of such energetic particles through the galactic and intergalactic magnetic fields may be nearly rectilinear, no astronomical sources have as yet been identified. This is the enigma of the highest-energy cosmic rays. The paper reviews the history of research in this energy regime and critically assesses the observational results on the energy spectrum, arrival directions, and composition of the primary cosmic rays based on observations made by six experiments. The detection methods currently available are described. Special techniques have been developed as particles of ${10}^{20}\mathrm{eV}$ or higher occur at a rate of only about 1 per ${\mathrm{km}}^{2}$ per century. Errors in measurement are given particular attention. The authors also review the theoretical predictions for a number of candidate sources of cosmic rays beyond the predicted cutoff. Finally, the four major projects planned to address the question of the origin of UHECRs are briefly described.
718 citations
Journal Article•
TL;DR: Gockel and Gockel as mentioned in this paper reported on the first of these to the scientific meeting of Karlsruhea In both flights no essential variation in the radiation could be observed up to heights of,aa meters.
Abstract: Last year I had the opportunity to investigate the penetrating radiation during two balloon flights. I reported on the first of these to the scientific meeting of Karlsruhea In both flights no essential variation in the radiation could be observed up to heights of ,aa meters. Gockel, also, in two balloon °ights, was unable to detect the expected diminution in intensity of the radiation with heighta From this it was con- cluded that besides the radiation from the radioactive element in the earth's crust there must be another source of penetrating radiationa Two Wulf radiation apparatuses of 3 mm, wall thickness were used for the observationsa Apparatus Noa I had an ionization cell with a value of 2a39 cc and a capacity of a59a cma Apparatus Noa 2 had a volume of 29aa cc and a capacity of aa9a cma A charge loss corresponding to a decrease of volt per hour thus rep- resented an intensity of ionization of = a56 ions per cc per second in Apparatus No and = aaa355 ions per cc per second in Apparatus Noa 2a Whereas all observers of the penetrating radiation on the top of towers have always con rmed a decrease of the penetrating radiation, Gockel and I in balloon °ights could not detect such a decrease with certaintya In order to obtain reliable mean values it was necessary to carry out observation in long lasting flights at modest heights.
466 citations