In-medium modification and decay asymmetry of omega mesons in cold nuclear matter

We discuss an asymmetry of the decay $\omega->e^+e^-$ in nuclear matter with respect to the electron and positron energies. This asymmetry is sensitive to the properties of the $\omega$ meson self-energy and, in particular, it has a non-trivial dependence on the $\omega$ energy and momentum. Therefore, this asymmetry may serve as a powerful tool in studying the properties of the $\omega$ meson in the nuclear medium.Comment: 19 pages, 9 figure

Selected vector-meson decay-distributions in reactions of polarized photons with protons

We develop a formalism for studying vector meson ($V$) photo-production at the proton ($p$) with polarized photons, $\vec\gamma p \to V p$, through an analysis of the decay distribution in the channel $V\to\pi^0\gamma$. We show that this decay distribution differs noticeably from the distributions of purely hadronic decays, like $\phi\to K^+K^-$, $\omega\to \pi^0\pi^+\pi^-$. Formulas for the decay distributions are presented which are suitable for data analysis and interpretation.Comment: 3 pages, 2 figure

Korshunov instantons out of equilibrium

Zero-dimensional dissipative action possesses non-trivial minima known as Korshunov instantons. They have been known so far only for imaginary time representation that is limited to equilibrium systems. In this work we reconstruct and generalise Korshunov instantons using real-time Keldysh approach. This allows us to formulate the dissipative action theory for generic non-equilibrium conditions. Possible applications of the theory to transport in strongly biased quantum dots are discussed..Comment: 6 pages, 2 figure

Isoscalar-Isovector Interferences in πN→Ne+e−\pi N \to N e^+ e^- Reactions as a Probe of Baryon Resonance Dynamics

The isoscalar-isovector ($\rho-\omega$) interferences in the exclusive reactions $\pi^- p \to n e^+ e^-$ and $\pi^+ n \to p e^+ e^-$ near the $\omega$ threshold leads to a distinct difference of the dielectron invariant mass distributions depending on beam energy. The strength of this effect is determined by the coupling of resonances to the nucleon vector-meson channels and other resonance properties. Therefore, a combined analysis of these reactions can be used as a tool for determining the baryon resonance dynamics

Production of \phi Mesons in Near-Threshold \pi N and N N Reactions

We analyze the production of $\phi$ mesons in $\pi N$ and NN reactions in the near-threshold region, using throughout the conventional ``non-strange'' dynamics based on such processes which are allowed by the non-ideal $\omega-\phi$ mixing. We show that the occurrence of the direct $\phi NN$ interaction may show up in different unpolarized and polarization observables in $\pi N\to N\phi$ reactions. We find a strong non-trivial difference between observables in the reactions $pp\to pp\phi$ and $pn\to pn\phi$ caused by the different role of the spin singlet and triplet states in the entrance channel. A series of predictions for the experimental study of this effect is presented.Comment: 35 pages including 18 figure

Diamagnetism of metallic nanoparticles as the result of strong spin-orbit interaction

The magnetic susceptibility of an ensemble of clean metallic nanoparticles is shown to change from paramagnetic to diamagnetic one with the onset of spin-orbit interaction. The effect is quantified on the basis of symmetry analysis with the help of the random matrix theory. In particular, the magnetic susceptibility is investigated as the function of symmetry breaking parameter representing magnetic flux in the crossover from symplectic to unitary and from orthogonal to unitary ensembles. Corresponding analytical and numerical results provide a qualitative explanation to the experimental data on diamagnetism of an ensemble of gold nanorods.Comment: 6 pages, 5 figures; extended versio

Exclusive charm production in pbar p collisions at s^1/2 <15 GeV

We discuss the open charm production in peripheral reactions $\bar pp\to \bar Y_cY_c$ and $\bar pp\to M_c\bar M_c$, where $Y_c$ and $M_c$ stand for $\Lambda_c^+,\Sigma_c^+$ and $D,D^*$, respectively, at $\sqrt{s}\lesssim 15$ GeV, which corresponds to the energy range of FAIR. Our consideration is based on the topological decomposition of the planar quark and diquark diagrams which allows to estimate consistently meson and baryon exchange trajectories and energy scale parameters as well. The spin dependence is determined by the effective interaction of lowest exchanged resonance. Unknown parameters are fixed by an independent analysis of open strangeness production in $\bar pp\to \bar YY$ and $\bar pp\to \bar KK$ reactions and of SU(4) symmetry. We present the corresponding cross sections and longitudinal double-spin asymmetries for exclusive binary reactions with open charm mesons and baryons in the final state. The polarization observables have a non-trivial $t$ and $s$ dependence which is sensitive to details of the open charm production mechanism.Comment: 26 pages, 18 figure

Magnon activation by hot electrons via non-quasiparticle states

We consider the situation when a femtosecond laser pulse creates a hot electron state in half-metallic ferromagnet (e. g. ferromagnetic semiconductor) on a picosecond timescale but do not act directly on localized spin system. We show that the energy and magnetic moment transfer from hot itinerant electrons to localized spins is facilitated by the so-called non-quasiparticle states, which are the scattering states of a magnon and spin-majority electron. The magnon distribution is described by a quantum kinetic equation that we derive using the Keldysh diagram technique. In a typical ferromagnetic semiconductor such as EuO magnons remain essentially in non-equilibrium on a scale of the order of microsecond after the laser pulse.Comment: 8 pages, 2 figure