The Tibet ASγ experiment just reported their measurement of sub-PeV diffuse gamma-ray emission from the Galactic disk, with highest energy up to 957 TeV. These gamma rays are most likely hadronic origin by cosmic ray (CR) interaction interstellar gas in galaxy. This provides direct evidence hypothesis that Cosmic Rays (GCRs) can be accelerated beyond PeV energies. In this work, we try explain s...

In this chapter I give an overview of shock acceleration , including a discussion of the maximum energies possible and the shape of the spectrum near cutoff , interactions of high energy cosmic rays with, and propagation through, the background radiation, and the resulting electron-photon cascade. Possible sources of the highest energy cosmic rays are discussed including active galaxies , gamma...

The first balloon flight of the TRACER instrument in 1999 led to a new measurement of the energy spectra of cosmic ray nuclei from Z=8 to Z=26 at energies from a few GeV/nucleon to several TeV/nucleon. We will present and discuss the results, compare them with other recent measurements and examine the implications for current cosmic ray propagation and acceleration models. Finally, we will comm...

Underground muon events detected by the MACRO experiment at Gran Sasso have been studied for different purposes. The studies include the vertical muon intensity measurement, multiplicity distribution, lateral and angular muon distribution and searches for substructures inside muon bundles. These analyses have contributed to bring new insights in cosmic ray physics, in particular in the framewor...

Present data on cosmic-ray elemental and isotopic relative abundances are shown to be unable to distinguish between various models of cosmic-ray sources and their composition. For example, the model of freshly nucleosynthesized material from supernova explosions as the cosmic-ray source is unable to account for some measured, key cosmic-ray elemental abundances. This and two other models are ev...

Precision measurements of the positron component in the cosmic radiation provide important information about the propagation of cosmic rays and the nature of particle sources in our Galaxy. The satellite-borne experiment PAMELA has been used to make a new measurement of the cosmic-ray positron flux and fraction that extends previously published measurements up to 300 GeV in kinetic energy. The ...

In this chapter I give an overview of shock acceleration , including a discussion of the maximum energies possible and the shape of the spectrum near cut-oo, interactions of high energy cosmic rays with, and propagation through, the background radiation, and the resulting electron-photon cascade. Possible sources of the highest energy cosmic rays are discussed including active galaxies , gamma ...

We present the results of a new estimation of the photodisintegration and propagation of ultrahigh energy cosmic-ray (UHCR) nuclei in intergalactic space. The critical interactions for energy loss and photodisintegration of UHCR nuclei occur with photons of the infrared background radiation (IBR). We have reexamined this problem making use of a new determination of the IBR based on empirical da...

The CEM2k and LAQGSM codes have been recently developed at Los Alamos National Laboratory to simulate nuclear reactions for a number of applications. We have benchmarked our codes against most available data measured at incident particle energies from 10 MeV to 800 GeV and have compared our results with predictions of other current models used by the nuclear community. Here, we present a brief ...

Scattering processes in the cosmic microwave background limit the propagation of ultra high energy charged particles in our Universe. For extragalactic proton sources resonant photopion production results in the famous Greisen-Zatsepin-Kuzmin (GZK) cutoff at about 4×10 GeV expected in the spectrum observed on Earth. The faint flux of ultra high energy cosmic rays of less than one event per year...