High Energy Cosmic Ray Nuclei Research Articles

Publisher’s Note: High-energy cosmic ray nuclei from tidal disruption events: Origin, survival, and implications [Phys. Rev. D 96 , 063007 (2017)

Publisher’s Note: High-energy cosmic ray nuclei from tidal disruption events: Origin, survival, and implications [Phys. Rev. D <b>96</b> , 063007 (2017)

High-energy cosmic ray nuclei from tidal disruption events: Origin, survival, and implications

Tidal disruption events (TDEs) by supermassive or intermediate mass black holes have been suggested as candidate sources of ultrahigh-energy cosmic rays (UHECRs) and high-energy neutrinos. Motivated by the recent measurements from the Pierre Auger Observatory, which indicates a metal-rich cosmic-ray composition at ultrahigh energies, we investigate the fate of UHECR nuclei loaded in TDE jets. First, we consider the production and survival of UHECR nuclei at internal shocks, external forward and reverse shocks, and nonrelativistic winds. Based on the observations of Swift J1644+57, we show that the UHECRs can survive for external reverse and forward shocks, and disk winds. On the other hand, UHECR nuclei are significantly disintegrated in internal shocks, although they could survive for low-luminosity TDE jets. Assuming that UHECR nuclei can survive, we consider implications of different composition models of TDEs. We find that the tidal disruption of main sequence stars or carbon-oxygen white dwarfs does not successfully reproduce UHECR observations, namely the observed composition or spectrum. The observed mean depth of the shower maximum and its deviation could be explained by oxygen-neon-magnesium white dwarfs, but they may be too rare to be the sources of UHECRs.

New measurements of the energy spectra of high-energy cosmic-ray protons and helium nuclei with the calorimeter in the PAMELA experiment

New measurements of the energy spectra of cosmic-ray protons and helium nuclei with significantly increased statistics owing to an improvement of the event selection technique and the involvement o ...

Analytic calculations of the spectra of ultra high energy cosmic ray nuclei. II. The general case of background radiation

We discuss the problem of ultra high energy nuclei propagation in extragalactic background radiations. The present paper is the continuation of the accompanying paper I where we have presented three new analytic methods to calculate the fluxes and spectra of ultra high energy cosmic ray nuclei, both primary and secondary, and secondary protons. The computation scheme in this paper is based on the analytic solution of coupled kinetic equations, which takes into account the continuous energy losses due to the expansion of the universe and pair-production, together with photo-disintegration of nuclei. This method includes in the most natural way the production of secondary nuclei in the process of photo-disintegration of the primary nuclei during their propagation through extragalactic background radiations. In paper I, in order to present the suggested analytical schemes of calculations, we have considered only the case of the cosmic microwave background radiation, in the present paper we generalize this computation to all relevant background radiations, including infra-red and visible/ultra-violet radiations, collectively referred to as extragalactic background light. The analytic solutions allow transparent physical interpretation of the obtained spectra. Extragalactic background light plays an important role at intermediate energies of ultra high energy cosmic ray nuclei. The most noticeable effect of the extragalactic background light is the low-energy tail in the spectrum of secondary nuclei.

High-energy cosmic-ray nuclei from high- and low-luminosity gamma-ray bursts and implications for multimessenger astronomy

Gamma-ray bursts (GRBs) are one of the candidates of ultrahigh-energy ($\ensuremath{\gtrsim}{10}^{18.5}\text{ }\text{ }\mathrm{eV}$) cosmic-ray (UHECR) sources. We investigate high-energy cosmic-ray acceleration including heavy nuclei in GRBs by using Geant 4, and discuss its various implications, taking both high-luminosity (HL) and low-luminosity (LL) GRBs into account. This is because LL GRBs may also make a significant contribution to the observed UHECR flux if they form a distinct population. We show that not only protons, but also heavier nuclei can be accelerated up to ultrahigh energies in the internal, (external) reverse, and forward shock models. We also show that the condition for ultrahigh-energy heavy nuclei such as iron to survive is almost the same as that for $\ensuremath{\sim}\mathrm{TeV}$ gamma rays to escape from the source and for high-energy neutrinos not to be much produced. The multimessenger astronomy by neutrino and GeV-TeV gamma-ray telescopes such as IceCube and KM3Net, GLAST and MAGIC will be important to see whether GRBs can be accelerators of ultrahigh-energy heavy nuclei. We also demonstrate expected spectra of high-energy neutrinos and gamma rays, and discuss their detectabilities. In addition, we discuss implications of the GRB-UHECR hypothesis. We point out, since the number densities of HL GRBs and LL GRBs are quite different, its determination by UHECR observations is also important.

Germ cell mutagenesis in medaka fish after exposures to high-energy cosmic ray nuclei: A human model

Astronauts beyond the Earth's orbit are exposed to high-energy cosmic-ray nuclei with high values of linear energy transfer (LET), resulting in much more biological damage than from x-rays or gamma-rays and may result in mutations and cancer induction. The relative biological effectiveness of these nuclei depends on the LET, rising to as high as approximately 50 at LET values of approximately 100-200 keV/microm. An endpoint of concern is germ cell mutations passed on to offspring, arising from exposure to these nuclei. A vertebrate model for germ cell mutation is Medaka fish (Oryzias latipes). We exposed wild type males to doses of 1 GeV per nucleon Fe nuclei or to 290 MeV per nucleon C nuclei. They were mated to females with recessive mutations at five-color loci. The transparent embryos from >100 days of mating (representing exposed sperm, spermatids, or spermatogonia) were observed so as to detect dominant lethal mutations and total color mutations, even though the embryos might not hatch. The relative number of mutant embryos as a function of dose were compared with those induced by gamma-rays. The relative biological effectiveness values for dominant lethal mutations and total color mutations for exposed sperm and spermatids were 1.3-2.1 for exposure to C nuclei and 1.5-3.0 for exposure to Fe nuclei. (The spermatogonial data were uncertain.) These low values, and the negligible number of viable mutations, compared with those for mutations in somatic cells and for neoplastic transformation, indicate that germ cell mutations arising from exposures to cosmic ray nuclei are not a significant hazard to astronauts.

High energy cosmic ray nuclei results on Ulysses: 1. Mission overview

High energy cosmic ray nuclei results on Ulysses: 1. Mission overview

High energy cosmic-ray nuclei results on Ulysses: 2. Effects of a recurrent high-speed stream from the southern polar coronal hole

High energy cosmic-ray nuclei results on Ulysses: 2. Effects of a recurrent high-speed stream from the southern polar coronal hole

High Energy cosmic neutrinos

We discuss the production of neutrinos in interactions of high energy cosmic ray nuclei accelerated in different astrophysical objects. Neutrino fluxes of different magnitude and energy spectra are produced in interactions on diffuse galactic matter and possibly at or close to the acceleration site. Different potential sources inside and outside our galaxy are discussed with an increased attention to neutrinos generated in photoproduction interactions at active galactic nuclei. The observability of these neutrinos with current and future generation detectors is estimated.

Nucleus-nucleus collisions and interpretation of cosmic-ray cascades.

We describe a multiple scattering model of nucleus-nucleus collisions for use in simulation of atmospheric cascades produced by high-energy cosmic-ray nuclei. We emphasize the importance of a realistic treatment of nuclear fragmentation of the incident nucleus for fluctuations in quantities such as high-energy muon bundles and longitudinal development of giant air showers. The model is realized in a cascade program that can be combined with any treatment of hadronic interactions.

Astromag: Particle astrophysics magnet facility for space station freedom

In June 1989 three particle astrophysics investigations were selected for the Astromag superconducting magnet facility to be flown as a U.S.-Italy project on Space Station Freedom in the late 1990s. The science goals include investigating the origin and evolution of matter in the galaxy by direct sampling of galactic material; examining cosmological models by searching for antimatter and evidence of the nature of dark matter; and studying the origin of extremely energetic particles and their effects on the dynamics and evolution of the galaxy. By augmenting Astromag's strong magnetic field with a variety of specialized detectors, state-of-the-art spectometers will be employed to address the experimental objectives. Measurements of high energy cosmic ray nuclei and electrons will be made with precision and sensitivity 10–1000 times that of previous experiments. The Space Station is an ideal spacecraft for Astromag, because it provides both the assembly and servicing capabilities needed for change-out of experiments and replenishment of liquid helium to extend the life of the facility.

Chemical Composition of High-Energy Cosmic-Ray Nuclei and its Possible Origin in Type-II Supernova

High energy cosmic ray spectrum has been known to have an interesting bump in the energy range 1014 − 1016 eV. Various models to explain the spectral break in this energy range have been so far proposed; which incorporate either a large-scale termination of galactic wind, shocks with greater age and spatial extent associated with hypothetical super-bubbles powered by multiple supernovae, intersection of two quantum-gravitational components, extra-galactic component, red-shift of big-bang remnant, or a proton component from pulsars. More recently, their possible origin in type-II supernovae with magnetic acceleration mechanism is proposed by considering direct observational results of chemical composition near the bump regime of cosmic ray spectrum.

Isotopic analysis of high energy cosmic-ray nuclei

The isotopic and chemical composition of primary cosmic-ray nuclei of a given magnetic rigidity does not change as the particles penetrate the magnetosphere. Their velocity spectra, however, are strongly modified. These modifications depend on the charge-to-mass ratio of each nuclear component. By comparing the velocity spectra of pairs of elements, their isotopic composition can be obtained. A detailed knowledge of geomagnetic cut-off values or of the transmission functions in the penumbra region is not required for such an analysis. The precision of isotopic composition analysis is limited by statistical fluctuation, nuclear interactions, and distortion of the velocity spectra by the measuring instruments. These effects have been evaluated. It is concluded that in the region of rigidities between 3 and 20 GV/ c a reasonably dimensioned Cherenkov counter telescope in a near-earth orbit, making use of established techniques, can measure with considerable precision the isotopic composition of the most abundant elements in the primary cosmic radiation including many elements of special interest from the astrophysical point of view.

Nuclear interactions by high-energy cosmic ray nuclei with light nuclei in emulsion

The mechanism of particle production in nucleus-nucleus and nucleus-nucleon collisions produced by high-energy cosmic ray nuclei (6<or=Z<or=26) in nuclear emulsion has been studied. Theoretical formulae to estimate the lntan theta distributions of the individual groups of secondaries have been derived and used for the analysis. It is found that a large proportion of relativistic alpha particles and protons are produced through the knock-on process as distinct from the fragmentation process. Kaplon's and the present formulae for the fragmentation alpha particles or protons if applied to all the relativistic alpha particles or protons, would give an underestimation of the primary energy. Mesons are produced more through the isobar than the fireball process in the primary energy interval from 10 to 30 GeV/nucleon, but the meson multiplicity due to the latter process increases faster with increasing energy than for the former process.

Determination of energy and charge spectra of high energy cosmic ray nuclei using gas Čerenkov counter

Suitability of gas Čerenkov counter for the determination of energy spectra of cosmic ray nuclei as well as charge composition from few GeV to few tens of GeV has been investigated in this paper. It is found that for a counter with 5 GeV/nuc threshold energy and 100 cm radiating length the energy resolution is 40% for proton up to 21 GeV and for alpha particles 30 GeV/nuc. With 10 GeV/nuc. threshold energy and for the same radiating length these limits are at 27.5 GeV for protons and 39 GeV/nuc. for alpha particles for the same resolution. This resolution, however, steadily improves at lower energies. These results show that gas Čerenkov counters are superior in resolving power to most of the ionization spectrometer likely to be constructed for balloon and satellite payload. Comparison with theoretical results show that ionization spectrometer in this energy interval has indeed inferior resolution.

Energy Loss of High-Energy Cosmic Rays in Pair-Producing Collisions with Ambient Photons

General and essentially exact formulas for the energy-loss process $A+\ensuremath{\gamma}\ensuremath{\rightarrow}A+{e}^{+}+{e}^{\ensuremath{-}}$ are given for high-energy cosmic-ray nuclei traversing an isotropic radiation field of arbitrary energy spectrum. These formulas are obtained by integrating the appropriate differential cross section in the rest frame of the cosmic-ray particle. Results are then given for the case of a Planckian photon distribution at arbitrary temperature. The effect of this energy loss on a universal flux of cosmic rays is then investigated along with the possibility that the observed "knee" at high energies is due to pair production. Finally, the energy-loss formula is applied to quasistellar objects, and it is shown that if these objects are at cosmological distances, they are opaque to particles above a certain energy which depends upon the size of the object.