Extraction of Kaon Formfactors from K^- -> mu^- nu_mu gamma Decay at ISTRA+ Setup

The radiative decay K->mu nu gamma has been studied at ISTRA+ setup in a new kinematical region. About 22K events of K^- -> mu^- nu_mu gamma have been observed. The sign and value of Fv-Fa have been measured for the first time. The result is Fv-Fa=0.21(4)(4).Comment: 11 pages, 21 figures, submitted to Phys. Lett.

Aspects of radiative K^+_e3 decays

We re-investigate the radiative charged kaon decay K+- --> pi0 e+- nu_e gamma in chiral perturbation theory, merging the chiral expansion with Low's theorem. We thoroughly analyze the precision of the predicted branching ratio relative to the non-radiative decay channel. Structure dependent terms and their impact on differential decay distributions are investigated in detail, and the possibility to see effects of the chiral anomaly in this decay channel is emphasized.Comment: 15 pages, 6 figure

Structure and Mechanical Properties of TiAlSiY Vacuum-Arc Coatings Deposited in Nitrogen Atmosphere

The effect of a negative bias potential applied to the substrate on elemental composition, structure, and mechanical properties of vacuum-arc TiAlSiY nitride coatings is investigated by different methods. It is ascertained that applying a high (up to –500 V) bias voltage leads to a selective sputtering of target as well as significant microdeformation of the coating, small-sized growth of crystallites, and their preferred orientation along the [110] direction. In this case, the coating deposited has a low hardness H = 6.95 GPa and propensity to intense wear under scratch and tribological tests. Crystallites with stoichiometric composition ~140 nm in size and [111] preferred orientation perpendicular to the surface of growth are formed at the bias potential about –200 V, and superhard (H = 49.5 GPa) and wear-resistant coatings are grown under such conditions. The mechanisms of formation of the structure of multielement coatings are discussed. It is shown that for- mation of an amorphous phase and nanocrystal [110] texture takes place at a high bias potential owing to the process of radiation-stimulated selective spraying of the target. Formation of microstrained crystallites 10 nm in size caused by the weakening of interatomic bonds is observed in the coating under such deposition condi- tions, and it leads to the decrease in coating hardness and fast destruction during tribological testing. Sub- stantial bias voltage dependence of deposited coating properties is established in our investigations

Search for a strongly decaying neutral charmed pentaquark

We present a search for a charmed pentaquark decaying strongly to $D^{(*)-}p$. Finding no evidence for such a state, we set limits on the cross section times branching ratio relative to $D^{*-}$ and $D^-$ under particular assumptions about the production mechanism.Comment: To be published in Physics Letters

Metal Matrix Composites Reinforced With Nanoparticles for the Needs of Space Exploration

International audienceAluminum (Al) matrix composite materials reinforced with small amounts (0,01 – 0,15 % vol.) of aluminum or zirconium oxides nanoparticles were fabricated by tradition powder metallurgy (PM) techniques with cold pressing and vacuum sintering. Nanoparticles and their clusters were located on grain boundaries of a matrix. The microhardness of the produced composites was dramatically increased than bulk pure Al, by increasing the amount of nanoparticles. The tensile strength of the produced composites was dramatically increased (more than 2 times) than bulk pure Al, by increasing the amount of nanoparticles. This powder metallurgical approach could also be applied to other nanoreinforced composites, such as ceramics or complex matrix materials