Aims. We investigate whether the high energy tail detected by the Fermi/LAT for the short GRB 081024B can be caused by synchrotron and self-Compton emission in the context of either the internal or external shock models. Methods. For the internal shock scenario, we explore the possibility of generating the high energy photons directly by means of the synchrotron process, or inverse Compton emis...

At high red shift, the temperature of cosmic microwave background is sufficiently high for the ultrahighenergy photons to pair-produce muons and pions through interactions with the background photons. At the same time, the radio background and magnetic fields are too weak to drain energy out of the electromagnetic cascade before the muons and pions are produced. Decays of the energetic muons an...

Using CompHEP package we’ve made the detailed estimate of the influence of double ee pair production (DPP) by photons on the propagation of ultra high energy electromagnetic (EM) cascade. We show that in the models in which cosmic ray photons energy reaches few×103 EeV refined DPP analysis may lead to substantial difference in predicted photon spectrum compared to previous rough estimates.

The density matrix is obtained for short-wavelength photons passing through a medium. For sufficiently large thicknesses of a target this matrix is expressed by the forward scattering amplitude of a photon. For multi-GeV photons scattering via virtual e+ e− pairs is the most important process. Its amplitude in a crystal is calculated. The results obtained are used to find the optimal thicknesse...

Introduction: In radionuclide imaging, object scatter is one of the major factors leading to image quality degradation. Therefore, the correction of scattered photons might have a great impact on improving the image quality. Regarding this, the present study aimed to determine the main and sub-energy windows for triple energy window (TEW) scatter correction method usin...

A tuneable repetition rate extreme ultraviolet source (Harmonium) for time resolved photoelectron spectroscopy of liquids is presented. High harmonic generation produces 30-110 eV photons, with fluxes ranging from ∼2 × 10(11) photons/s at 36 eV to ∼2 × 10(8) photons/s at 100 eV. Four different gratings in a time-preserving grating monochromator provide either high energy resolution (0.2 eV) or ...

The observation of photons with energies above 10 eV would open a new window in cosmic-ray research, with possible impact on astrophysics, particle physics, cosmology and fundamental physics. Current and planned air shower experiments, particularly the Pierre Auger Observatory, offer an unprecedented opportunity to search for such photons and to complement efforts of multi-messenger observation...

The possibility of discerning extensive air showers initiated by ultra-high energy (UHE) photons from those induced by hadrons is studied. Two effects characteristic only for UHE photons are taken into account: LPM effect and photon conversion/cascading in the geomagnetic field. First conclusions about the possibility of identification of photons in the UHE cosmic-ray spectrum are presented and...

A search for new particle s which might be produced by photons of energy up to 18 GeV is described. No new particles were found. Calculations of the Beth&-Heitler process are described which make it possible to state that this exper.iment would have detected non-strongly interacting particles whose mass and lifetime lay in a definite range, did they exist.

The processes of double ionization by absorption or inelastic (Compton) scattering of a photon from atomic systems are of fundamental interest. This is due to the fact that the two-electron emission is exclusively caused by the electron-electron interaction, the accurate treatment of which is still one of the main tasks for different theoretical approaches. As a target, it is usual to use the n...