The production and annihilation of antiprotons in the hadronic phase of heavy-ion collisions is evaluated within a thermal equilibrium approach. It is shown that the inverse reaction of pp̄ annihilation (i.e., multi-pion annihilation Nππ → pp̄ with Nπ ≃ 5-7) in connection with oversaturation of pion phase space (i.e., finite pion chemical potentials) plays an important role in understanding the o...

In this note D9and anti-D9-brane annihilation in type I string theory is probed by a D1-brane. We consider the covariant Green-Schwarz or twistor formulation of the probe theory. We expect the theory to be κ-invariant after the annihilation is completed. Conditions of the κ-invariance of the theory impose constraints on the background tachyon field. Solutions to the constraints define tachyon v...

The Galactic positrons, as observed by their annihilation gamma-ray line at 0.511 MeV, are difficult to account for with astrophysical sources. It has been proposed that they are produced instead by dark matter annihilation or decay in the inner Galactic halo. To avoid other constraints, these processes are required to occur "invisibly," such that the eventual positron annihilation is the only ...

Nanoparticles embedded in a matrix can trap positrons under certain conditions. In such cases nanoparticles can be effectively studied by means of positron annihilation because positron annihilation characteristics contain information related to nanoparticles’ electronic and atomic structure. Of great importance is to calculate the positron response from such nanoparticles. Then, nanoparticles ...

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 par...

The order and the nature of the finite-temperature phase transition of QCD with two flavors of dynamical quarks is investigated. An analysis of the critical exponent of the specific heat is performed through finite-size and finite-mass scaling of various susceptibilities. Dual superconductivity of QCD vacuum is investigated using a disorder parameter, namely the v.e.v. of a monopole creation op...

In this paper all deformations of the general linear group, subject to certain restrictions which in particular ensure a smooth passage to the Lie group limit, are obtained. Representations are given in terms of certains sets of creation and annihilation operators. These creation and annihilation operators may belong to a generalisation of the q-quark type or q-hadronic type, of q-boson or q-fe...

Annihilation of the electron-positron pairs (or (e−, e)−pairs, for short) in various polyelectrons e n e− m = e− m e n (where n ≥ 1 and m ≥ 1) is considered. In particular, we discuss the threeand four-photon annihilation of the (e−, e)−pairs in the three-body Ps− ion and four-body bi-positronium system Ps2. It is shown that the five-body e + 2 e − 3 ion is an unbound system. The closed form ex...

We analyze the decay B → φK within the framework of QCD-improved factorization. We found that although the twist-3 kaon distribution amplitude dominates the spectator interactions, it will suppress the decay rates slightly. The weak annihilation diagrams induced by (V −A)(V +A) penguin operators, which are formally power-suppressed by order (ΛQCD/mb) 2, are chirally and in particular logarithmi...