Channel coupling effects in ρ\rho-meson photoproduction

We investigate $\rho$-meson photoproduction in a coupled-channels formulation. It is shown that channel coupling effects are large and account for discrepancies observed in several single-channel treatments.Comment: 8 pages, 5 figures; small textual corrections and notation change

K-Lambda and K-Sigma photoproduction in a coupled channels framework

A coupled channels analysis, based on the K-matrix approach, is presented for photo-induced kaon production. It is shown that channel coupling effects are large and should not be ignored. The importance of contact terms in the analysis, associated with short range correlations, is pointed out. The extracted parameters are compared with SU(3)-model predictions.Comment: 15 pages, 10 figures; Submitted to Physical Review C. v2: A figure showing the effect of P13(1900) added v3: Small spelling corrections, one reference update

Interaction effects in assembly of magnetic nanoparticles

A specific absorption rate of a dilute assembly of various random clusters of iron oxide nanoparticles in alternating magnetic field has been calculated using Landau- Lifshitz stochastic equation. This approach simultaneously takes into account both the presence of thermal fluctuations of the nanoparticle magnetic moments, and magneto-dipole interaction between the nanoparticles of the clusters. It is shown that for usual 3D clusters the intensity of magneto- dipole interaction is determined mainly by the cluster packing density eta = Np*V/Vcl, where Np is the average number of the particles in the cluster, V is the nanoparticle volume, and Vcl is the cluster volume. The area of the low frequency hysteresis loop and the assembly specific absorption rate have been found to be considerably reduced when the packing density of the clusters increases in the range of 0.005 < eta < 0.4. The dependence of the specific absorption rate on the mean nanoparticle diameter is retained with increase of eta, but becomes less pronounced. For fractal clusters of nanoparticles, which arise in biological media, in addition to considerable reduction of the absorption rate, the absorption maximum is shifted to smaller particle diameters. It is found also that the specific absorption rate of fractal clusters increases appreciably with increase of the thickness of nonmagnetic shells at the nanoparticle surfaces.Comment: The paper is accepted for Nanoscale Res. Let

Multi-reaction-channel fitting calculations in a coupled-channel model:Photoinduced strangeness production

To describe photo- and meson-induced reactions on the nucleon, one is faced with a rather extensive coupled-channel problem Ignoring the effects of channel coupling, as one would do in describing a certain reaction at the tree level; invariably creates a large inconsistency between the different reactions that are described In addition, the imaginary parts of the amplitude, which are related through the optical theorem, to total cross-sections, are directly reflected in certain polarization observables. Performing a full coupled-channel calculation thus offers the possibility to implement the maximum number of constraints The drawback one is faced with is to arrive at a simultaneous fit of a large number of reaction channels. While some of the parameters are common to many reactions; one is still faced with the challenge to optimize a large number of parameters in a highly non-linear calculation Here we show that such an approach is possible and present some results for photoinduced strangeness productio