Chiral Magnetic Skyrmions with Arbitrary Topological Charge ("skyrmionic sacks")

We show that continuous and spin-lattice models of chiral ferro- and antiferromagnets provide the existence of an infinite number of stable soliton solutions of any integer topological charge. A detailed description of the morphology of new skyrmions and the corresponding energy dependencies are provided. The considered model is general, and is expected to predict a plethora of particle-like states which may occur in various chiral magnets including atomic layers, e.g., PdFe/Ir(111), rhombohedral GaV$_4$S$_8$ semiconductor, B20-type alloys as Mn$_{1-x}$Fe$_x$Ge, Mn$_{1-x}$Fe$_x$Si, Fe$_{1-x}$Co$_x$Si, Cu$_2$OSeO$_3$, acentric tetragonal Heusler compounds

New type of stable particle like states in chiral magnets (Chiral bobbers)

We present a new type of a thermodynamically stable magnetic state at interfaces and surfaces of chiral magnets. The state is a soliton solution of micromagnetic equations localized in all three dimensions near a boundary and contains a singularity, but nevertheless has a finite energy. Both features combine to a quasi-particle state for which we expect unusual transport and dynamical properties. It exhibits high thermal stability and thereby can be considered as promising object for fundamental research and practical applications in spintronic devices. We provide arguments that such a state can be found in different B20-type alloys e.g. Mn$_{1-x}$Fe$_x$Ge, Mn$_{1-x}$Fe$_x$Si, Fe$_{1-x}$Co$_x$Si.Comment: accepted in PR

Two-particle decays of B_c meson into charmonium states

The factorization of hard and soft contributions into the hadronic decays of B_c meson at large recoils is explored in order to evaluate the decay rates into the S, P and D-wave charmonia associated with rho and pi. The constraints of approach applicability and uncertainties of numerical estimates are discussed. The mode with the J/psi in the final state is evaluated taking into account the cascade radiative electromagnetic decays of excited P-wave states, that enlarges the branching ratio by 20-25%.Comment: 13 pages, LaTeX axodraw-style, 1 figure, 2 table

Semileptonic Bc−→D∗0ℓνB_{c}^{-}\to D^{*0}\ell\nu transition in three--point QCD sum rules and HQET with gluon condensate corrections

Taking into account the gluon condensate contributions, the form factors of the semileptonic $B_c^- \to D^{*0}\ell\nu$ transition with $l=\tau, e$ are calculated in the framework of the three point QCD sum rules. The heavy quark effective theory limit of the form factors are also computed. The relevant total decay width as well as the branching ratio are evaluated and compared with the predictions of the other non-perturbative approaches.Comment: 27 Pages, 4 Figures and 4 Table

Theory of stripe domains in magnetic shape memory alloys

The evolution of multivariant patterns in thin plates of magnetic shape memory materials with an applied magnetic field was studied theoretically. A geometrical domain-model is considered composed of straight stripe-like martensite variants with constant internal magnetization (high anisotropy limit) and magnetic domain wall orientation fixed by the twin boundaries. Through integral transforms of the demagnetization energy, the micromagnetic energy is cast into a form convenient for direct numerical evaluation and analytical calculations. The equilibrium geometrical parameters of multivariant patterns with straight and oblique twin boundaries have been derived as functions of the applied field and the material parameters of a plate. It is shown that the oblique multivariant states exist only in plates with thicknesses L larger than a certain critical value L_0. In samples with L < L_0 a magnetic-field-driven transformation occurs directly between single variant states.Comment: Materials for E-MRS Fall Meeting, Warsaw 2007. Corrected figure

Leptonic constant of pseudoscalar B_c meson

We calculate the leptonic constant for the ground pseudoscalar state of B_c meson in the framework of QCD-motivated potential model taking into account the two-loop anomalous dimension for the heavy quark current in the nonrelativistic QCD as matched with the full QCD.Comment: 6 pages, RevTeX4 file, 3 eps-figures, several references and remarks adde

Prospects for the Bc Studies at LHCb

We discuss the motivations and perspectives for the studies of the mesons of the (bc) family at LHCb. The description of production and decays at LHC energies is given in details. The event yields, detection efficiencies, and background conditions for several Bc decay modes at LHCb are estimated.Comment: 20 pages, 5 eps-figure