Phase transition in annihilation-limited processes

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 tend to infinity, so that the annihilation rate times a certain power of the initial values of the average number of the particles remain constant (the double scaling) then if the initial state of the system is a multi-Poisson distribution, the system always remains in a state of multi-Poisson distribution, but with evolving parameters. The large time behavior of the system is also investigated. The system exhibits a dynamical phase transition. It is seen that for a k-particle annihilation, if k is larger than a critical value k_c, which is determined by the type-change rates, then annihilation does not enter the relaxation exponent of the system; while for k < k_c, it is the annihilation (in fact k itself) which determines the relaxation exponent.     

Dark matter spikes and annihilation radiation from the galactic center

The annihilation rate of weakly interacting cold dark matter particles at the galactic center could be greatly enhanced by the growth of a density spike around the central supermassive black hole (SBH). Here we discuss the effects of hierarchical mergers on the central spike. Mergers between halos containing SBHs lead to the formation of SBH binaries which transfer energy to the dark matter particles, lowering their density. The predicted flux of annihilation photons from the galactic center is several orders of magnitude smaller than in models that ignore the effects of SBHs and mergers. Measurement of the annihilation radiation could in principle be used to constrain the merger history of the galaxy.     

Creation and annihilation phenomena of electron and positron pairs in an oscillating field

The combination of an oscillating and a static field is used to study the creation and annihilation phenomena during the pair creation process. The time evolution, spatial density and momentum distribution of the created particles for a fermionic system are presented, which demonstrate that with the increasing static field intensity, the number of the created particles experiences a distinguishable decrease in every period of the oscillating field, which is caused by the annihilation phenomena between the created electrons and positrons.     

Self-trapping of positively charged particles in metals

It is shown that the existence of a metastable state in which positrons in metals are “self-trapped” by strong interaction with the lattice gives rise to an anomalous temperature dependence in positron annihilation properties. The “intermediate” temperature variation of the shape of the annihilation photon line discovered by MacKenzieet al. is well accounted for by this mechanism; alternative interpretations in terms of thermal expansion effects may be refuted. This result calls for considerable revision of some of the published monovacancy formation energies obtained from positron annihilation measurements. Approximate criteria for the existence and the metastability of a selftrapped state of positively charged particles in metals are given. It is found that metastable self-trapping may occur for positrons; hydrogen isotopes and positive muons should be self-trapped in configurations that are always stable relative to the Bloch-wave states of these particles.     

THE CONTROLLED ANNIHILATION PRINCIPLE OF PARTICLES AND ANTIPARTICLES

In this paper, a controlled annihilation principle of particles and antiparticles is suggested. The particles and antiparticles are kept in a common space by an electromagnetic field to form an equipartisma or semiequipartisma. The equipartisma and simiequipartisma are new meaterial form, they can annihilate themselves and liberate their energy at usual temperature. One may control the annihilation life-time and energy liberated speed with adjustment of the particle and antiparticle density.     

Signals of excited quarks and leptons

e⁺e^? annihilation to two photons (including beam polarization) and quark-antiquark annihilation to gluons are discussed as possible tools to investigate the existence (and handedness) of excited electrons and quarks. Properties of these particles can also be explored in eγ and ep colliders; production cross sections and the impact of these particles on structure functions are derived.     

Nonlinearity of Quantum Mechanics and Solution of the Problem of Wave Function Collapse

The problem of the wave function collapse (a problem of measurement in quantum mechanics) is considered. It is shown that it can be solved based on quantum mechanics and does not require any additional assumptions or new theories. The particle creation and annihilation processes, which are described based on quantum field theory, play a key role in the measurement processes. Superposition principle is not valid for the system of equations of quantum field theory for particles and fields, because this system is a non-linear. As a result of the creation (annihilation) of a particle, an additional uncertainty arises, which "smears" the interference pattern. The imposition of such a large number of uncertainties in the repetitive measurements leads to the classical behavior of particles. The decoherence theory also implies the creation and annihilation of particles, and this processes are the consequence of non-linearity of quantum mechanics. In this case, the term "collapse of the wave function" becomes a consequence of the other statements of quantum mechanics instead of a separate postulate of quantum mechanics.     

Nonlinearity of Quantum Mechanics and Solution of the Problem of Wave Function Collapse

The problem of the wave function collapse(a problem of measurement in quantum mechanics) is considered.It is shown that it can be solved based on quantum mechanics and does not require any additional assumptions or new theories. The particle creation and annihilation processes, which are described based on quantum field theory, play a key role in the measurement processes. Superposition principle is not valid for the system of equations of quantum field theory for particles and fields, because this system is a non-linear. As a result of the creation(annihilation) of a particle,an additional uncertainty arises, which "smears" the interference pattern. The imposition of such a large number of uncertainties in the repetitive measurements leads to the classical behavior of particles. The decoherence theory also implies the creation and annihilation of particles, and this processes are the consequence of non-linearity of quantum mechanics. In this case, the term "collapse of the wave function" becomes a consequence of the other statements of quantum mechanics instead of a separate postulate of quantum mechanics.     

Estimation of the Density of the Self-Interacting Dark-Matter Component within a Clump with Allowance for Recombination

The model of dark matter featuring a component in the form of free particles and antiparticles (a, ā ) possessing self-interaction of the Coulomb type is considered. Darkmattermay form small-scale clumps where the annihilation of particles a and ā is enhanced. This annihilation may lead to observable effects (in cosmic rays, for example) and/or to the destruction of these clumps. However, there is an ambiguity in describing the annihilation (via recombination) of very slow particles, which may include a and ā in clumps. The effect of annihilation (in terms of the residual number of free particles a and ā in clumps) is estimated within two approaches (simplified quantum-mechanical and classical) at chosen parameter values.     

Upper bound on the dark matter total annihilation cross section

We consider dark matter annihilation into standard model particles and show that the least detectable final states, namely, neutrinos, define an upper bound on the total cross section. Calculating the cosmic diffuse neutrino signal, and comparing it to the measured terrestrial atmospheric neutrino background, we derive a strong and general bound. This can be evaded if the annihilation products are dominantly new and truly invisible particles. Our bound is much stronger than the unitarity bound at the most interesting masses, shows that dark matter halos cannot be significantly modified by annihilations, and can be improved by a factor of 10-100 with existing neutrino experiments.     

Annihilating cold dark matter

Structure formation with cold dark matter (CDM) predicts halos with a central density cusp, which are observationally disfavored. If CDM particles have an annihilation cross section sigmav approximately 10(-29)(m/GeV) cm(2), then annihilations will soften the cusps. We discuss plausible scenarios for avoiding the early Universe annihilation catastrophe that could result from such a large cross section. The predicted scaling of core density with halo mass depends upon the velocity dependence of sigmav, and s-wave annihilation leads to a core density nearly independent of halo mass, which seems consistent with observations.     

A study of the sintering effect on ultrafine silver particles by means of positron annihilation

Angular correlation curves of two-photon annihilation in ultrafine silver particles are shown to become similar to that of bulk silver with increasing degree of sintering.     

On the four-photon annihilation of the electron-positron pairs

The four-photon annihilation of electron-positron pairs is considered. In our treatment the energies of the colliding particles can be arbitrary. We also discuss the lower-energy limit of the cross-section of three-photon annihilation of the (e^-, e⁺)-pair.     

Phase transition in a three-states reaction-diffusion system

A one-dimensional reaction-diffusion model consisting of two species of particles and vacancies on a ring is introduced. The number of particles in one species is conserved while in the other species it can fluctuate because of creation and annihilation of particles. It has been shown that the model undergoes a continuous phase transition from a phase where the currents of different species of particles are equal to another phase in which they are different. The total density of particles and also their currents in each phase are calculated exactly.     

Instabilities and Annihilation Blockade of Macrospheres in the Gravitationally Neutral Universe Model

Corrections to the spectra describing Jeans instability and acoustic vibrations due to the consideration of annihilation processes in the hydrodynamic model of the gravitationally neutral Universe are obtained. The problem of annihilation of galactic clusters and anticlusters arising at the stages of the formation of massive gravitational clusters in the period following recombination of charged particles of the early Universe is also discussed. By the example of spherical macroscopic objects, it is shown that gravitational repulsion between cluster and anticluster results in the impossibility of their annihilation due to the existence of the finite closest approach distance if the latter exceeds the distance between macrosphere centers.     

A useful quantity for studying jet structure in e+e− annihilation

We propose a new variable for studying the deviation from perfect two-jet structure in e⁺e^? annihilation. This involves only charged particles in the final state. We calculate this in QCD. We also discover a strong-interaction independent prediction in e⁺e^? annihilation.     

Constraints on dark matter annihilation from M87

As the largest mass concentrations in the local Universe, nearby clusters of galaxies and their central galaxies are prime targets in searching for indirect signatures of dark matter annihilation (DMA). We seek to constrain the dark matter annihilation emission component from multi-frequency observations of the central galaxy of the Virgo cluster. The annihilation emission component is modeled by the prompt and inverse-Compton gamma rays from the hadronization of annihilation products from generic weakly interacting dark matter particles. This component is fitted to the excess of the observed data above the spectral energy distribution (SED) of the jet in M87, described with a best-fit synchrotron-self-Compton (SSC) spectrum. While this result is not sufficiently significant to claim a detection, we emphasize that a dark matter “double hump signature” can be used to unambiguously discriminate the dark matter emission component from the variable jet-related emission of M87 in future, more extended observation campaigns.     

One-photon annihilation of an electron-positron pair in the field of pulsed circularly polarized light wave

The one-photon annihilation of an electron-positron pair in the pulsed light field is investigated theoretically. The pulsed laser field is described by the plane circularly polarized electromagnetic wave with the envelope function. The analytical expressions for an amplitude and probability of the studied process are derived. The conditions for an observation of the one-photon annihilation the pulsed light field are ascertained. It is demonstrated, that the region of numerical values of the initial particles parameters within which the one-photon annihilation in the pulsed light field may be possibly realized is significantly broader in comparison with the monochromatic wave case. Within the observation domain the probability of one-photon annihilation process in the pulsed light field essentially exceeds the correspondent one the external field absence, except the points with the strong suppression of the probability which is the result of an interference of the amplitude’s parts; the last ones correspond to the contributions of the front and posterior segments of the pulse.     

Anti-deuterons from heavy Dark Matter

We study the fluxes of anti-deuterons that could be produced by annihilations in the galactic halo of Dark Matter particles with multi-TeV mass and a large annihilation cross section, as indicated by the recent PAMELA results. The model of Minimal Dark Matter (MDM) is an example in this category. We find that the fluxes are well within the reach of planned experiments for DM candidates that annihilate mainly into quark pairs, and also extend into the multi-GeV range above the expected astrophysical background. They are instead less promising if the main annihilation channel is into gauge bosons.