High-energy photons from pair annihilation of dark matter particles contribute to the cosmic gamma-ray background (CGB) observed in a wide energy range. Since dark matter particles are weakly interacting, annihilation can happen only in high density regions such as dark matter halos. The precise shape of the energy spectrum of CGB depends on the nature of dark matter particles — their mass and ...

In the literature on positron annihilation lifetime spectroscopy (PALS) numerous papers are devoted to the temperature dependence of annihilation parameters: lifetime and relative intensity of various modes of decay. The number of studies on pressure dependence of the same parameters is in great contrast to the previously mentioned: the number is very low. The pressure studies certainly deserve...

A system of particles is studied in which the stochastic processes are one-particle type-change (or one-particle diffusion) and multi-particle annihilation. It is shown that, if the annihilation rate tends to zero but the initial values of the average number of the particles tends to infinity, so that the annihilation rate times a certain power of the initial values of the average number of the...

On the basis of phenomenological model of the orthopositronium annihilation ‘isotope anomaly’ in gaseous neon (lifetime spectra, positrons source Na) the realistic estimation of an additinal mode (∼ 0.2%) of the orthopositronium annihilation is received. PACS: 36.10.Dr, 13.90.+i, 06.09.+v In huge volume of the data on lifetime spectra of annihilation in substance of positrons from β-decay Na Na...

In light harvesting complex II (LHCII) of higher plants and green algae, carotenoids (Cars) have an important function to quench chlorophyll (Chl) triplet states and therefore avoid the production of harmful singlet oxygen. The resulting Car triplet states lead to a non-linear self-quenching mechanism called singlet-triplet (S-T) annihilation that strongly depends on the excitation density. In ...

We discuss the possibility to observe the products of dark matter annihilation that was going on in the early Universe. Of all the particles that could be generated by this process we consider only photons, as they are both uncharged and easily detectable. The earlier the Universe was, the higher the dark matter concentration n and the annihilation rate (proportional to n) were. However, the em...

The outcomes of annihilation are known, including some of the intermediary products, and the process can be represented by Feynman diagrams and modelled mathematically. However the mechanisms of annihilation at a deeper fundamental level are unknown. How exactly does matter and antimatter convert into photons? How does mass change into energy? This paper develops an answer by providing a theory...

Large positron annihilation cross sections have been observed for a variety of molecules at various energies below the threshold for positronium formation. These large values are due to vibrational Feshbach resonances VFRs , in which the positron attaches to the molecule while exciting a vibration. This leads to rates of annihilation far greater than those expected for a simple collision. The d...