Related papers: On parton distributions in a photon gas
Ultrahigh energy neutrinos can provide important information about the distant astronomical objects and the origin of the Universe. Precise knowledge about their interactions and production rates is essential for estimating background,…
Generalized parton distributions (GPDs) have become a standard QCD tool for analyzing and parametrizing the non perturbative parton structure of hadron targets. GPDs might be viewed as non-diagonal overlaps of light-cone wave functions and…
We obtain the photon spectrum induced by a cosmic background of unstable neutrinos. We study the spectrum in a variety of cosmological scenarios and also we allow for the neutrinos having a momentum distribution (only a critical matter…
Synchrotron radiation from cosmic rays is a key observational probe of the galactic magnetic field. Interpreting synchrotron emission data requires knowledge of the cosmic ray number density, which is often assumed to be in energy…
Various jet observables in photoproduction are studied and compared to data from HERA. The feasibility of using a dijet sample for constraining the parton distributions in the photon is then studied. For the current data the experimental…
We explore scenarios where the highest energy cosmic rays are produced by new particle physics near the grand unification scale. Using detailed numerical simulations of extragalactic nucleon, gamma-ray, and neutrino propagation, we show the…
After the successful detection of cosmic high-energy neutrinos, the field of multiwavelength photon studies of active galactic nuclei (AGN) is entering an exciting new phase. The first hint of a possible neutrino signal from the blazar TXS…
The observation of the diffuse Galactic gamma ray flux is the most powerful tool to study cosmic rays in different regions of the Galaxy, because the energy and angular distributions of the photons encode information about the density and…
We briefly recall the main physical features of the parton distributions in the quantum statistical picture of the nucleon. Some predictions from a next-to-leading order QCD analysis are compared to recent experimental results.
Existing and planned observatories for cosmic neutrinos open up a huge window in energy from 10^7 to 10^17 GeV. Here, we discuss in particular the possibilities to use extremely energetic cosmic neutrinos as a diagnostic of astrophysical…
The Compton process with the initial states of photons and neutrons described by the density matrices of a general form is studied for low energies of photons. The coherent contribution to the inclusive probability to record a photon is…
Compton scattering is a key process shaping spectra formation and accretion flow dynamics in accreting strongly magnetized neutron stars. A strong magnetic field affects the scattering cross section and makes it dependent on photon energy,…
At energies above the threshold for $W$ production the process $\nu \gamma \to l W^+$ is competive with $\nu \nu$ scattering at the same center of mass energies. In a cosmological setting, absorption of ultra high energy neutrinos by the…
The carrier or medium of electromagnetic waves has been vainly searched for many years, and now it has been caught after the establishment of the dynamic equations in photon gas. The photon's rest mass has been estimated from the cosmic…
In the inner regions of an accretion disk around a black hole, relativistic protons can interact with ambient matter to produce electrons, positrons and $\gamma$-rays. The resultant steady state electron and positron particle distributions…
High-energy cosmic ray electrons interaction with Dark Matter particles are considered. In particular, a weakening of energy spectrum of cosmic electrons is predicted resulting from inelastic electron scattering on hyper-pions in the…
The QCD treatment of the parton structure of virtual photons is briefly recalled, and possible limitations and open questions are pointed out. Various models for these densities are compared, completed by a short discussion of the treatment…
The dilute ionized gas is very popular in the Universe. Usually only the Compton interactions, the "Sunyaev-Zel'dovich" effect, were considered while photons propagated in this medium. In this paper the "soft-photon process" is considered.…
Physics perspectives are shown for future experiments in electron or positron scattering on nucleons, towards a deep and comprehensive understanding of the angular momentum structure of the nucleon in the context of Quantum Chromodynamics.…
We argue that existing measurements of ep collisions at HERA --in which an energetic photon is made via a QED `Compton' subprocess-- can provide rather detailed information on the photonic parton density of the proton. This function and its…