Transmission electron microscopy and x-ray diffraction investigation of the microstructure of nanoscale multilayer TiAlN/VN grown by unbalanced magnetron deposition

Cubic NaCl-B1 structured multilayer TiAlN/VN with a bi-layer thickness of approximately 3 nm and atomic ratios of (Ti+Al)/V = 0.98 to 1.15 and Ti/V = 0.55 to 0.61 were deposited by unbalanced magnetron sputtering at substrate bias voltages between -75 and -150 V. In this paper, detailed transmission electron microscopy and x-ray diffraction revealed pronounced microstructure changes depending on the bias. At the bias -75 V, TiAlN/VN followed a layer growth model led by a strong (110) texture to form a T-type structure in the Thornton structure model of thin films, which resulted in a rough growth front, dense columnar structure with inter-column voids, and low compressive stress of -3.8 GPa. At higher biases, the coatings showed a typical Type-II structure following the strain energy growth model, characterized by the columnar structure, void-free column boundaries, smooth surface, a predominant (111) texture, and high residual stresses between -8 and -11.5 GPa

Performance of nano-structured multilayer PVD coating TiAlN/VN in dry high speed milling of aerospace aluminium 7010-T7651

A low-friction and wear resistant TiAlN/VN multilayer coating with TiAlN/VN bilayer thickness 3 nm has been grown by using the combined cathodic arc etching and unbalanced magnetron sputtering deposition on high speed steel tools for dry cutting of aluminium alloys. In this paper, in-lab and industrial high speed milling tests have been performed on an aerospace aluminium alloy 7010-T7651. The results show that the TiAlN/VN coated tools achieved lower cutting forces, lower metal surface roughness, and significantly longer tool lifetime by three times over the uncoated tools as a result of the low friction and eliminated tool-metal adhesion. Under the same conditions, a TiAlN based multicomponent coating TiAlCrYN also increased the tool lifetime by up to 100% despite the high cutting forces measured

Electromagnetic Meson Form Factors in the Salpeter Model

We present a covariant scheme to calculate mesonic transitions in the framework of the Salpeter equation for $q\bar{q}$-states. The full Bethe Salpeter amplitudes are reconstructed from equal time amplitudes which were obtained in a previous paper\cite{Mue} by solving the Salpeter equation for a confining plus an instanton induced interaction. This method is applied to calculate electromagnetic form factors and decay widths of low lying pseudoscalar and vector mesons including predictions for CEBAF experiments. We also describe the momentum transfer dependence for the processes $\pi^0,\eta,\eta'\rightarrow\gamma\gamma^*$.Comment: 22 pages including 10 figure

On the Particle Data Group evaluation of Psi' and chi_c Branching Ratios

I propose a new evaluation of $\psi'(2S)$ and $\chi_c(1P)$ branching ratios which avoids the correlations affecting the current Particle Data Group evaluation. These correlations explain the apparent technique-dependent discrepancies between the available determinations of the ${\cal B}(\chi_c(1P)\to p\bar p)$ and $\Gamma(\chi_c(1P)\to \gamma\gamma)$ under the hypotesis that the current values of the $\psi'(2S)\to\chi_c(1P)\gamma$ branching ratios are overestimated. In the process I also noticed that Particle Data Group has not restated many of the older measurements, when necessary, for the new value of ${\cal B}(J/\psi\to l^+l^-)$, which significantly affects the evaluation of some relevant $\psi'(2S)$ and $\chi_c(1P)$ exclusive branching ratios.Comment: 13 pages. Revised version. Submitted to Phys. Rev.

Towards resolution of the scalar meson nonet enigma

By the application of a linear mass spectrum to a composite system of both the pseudoscalar and scalar meson nonets, we find three mass relations for the masses of the scalar states which suggest the $q\bar{q}$ assignment for the scalar meson nonet: $a_0(1320),$ $K_0^\ast (1430),$ $f_0(1500),$ $f_0'(980).$Comment: 16 pages, LaTe

A unified meson-baryon potential

We study the spectra of mesons and baryons, composed of light quarks, in the framework of a semirelativistic potential model including instanton induced forces. We show how a simple modification of the instanton interaction in the baryon sector allows a good description of the meson and the baryon spectra using an interaction characterized by a unique set of parameters.Comment: 7 figure

Baryon spectra with instanton induced forces

Except the vibrational excitations of $K$ and $K^*$ mesons, the main features of spectra of mesons composed of quarks $u$, $d$, and $s$ can be quite well described by a semirelativistic potential model including instanton induced forces. The spectra of baryons composed of the same quarks is studied using the same model. The results and the limitations of this approach are described. Some possible improvements are suggested.Comment: 5 figure

Strong Decays of Strange Quarkonia

In this paper we evaluate strong decay amplitudes and partial widths of strange mesons (strangeonia and kaonia) in the 3P0 decay model. We give numerical results for all energetically allowed open-flavor two-body decay modes of all nsbar and ssbar strange mesons in the 1S, 2S, 3S, 1P, 2P, 1D and 1F multiplets, comprising strong decays of a total of 43 resonances into 525 two-body modes, with 891 numerically evaluated amplitudes. This set of resonances includes all strange qqbar states with allowed strong decays expected in the quark model up to ca. 2.2 GeV. We use standard nonrelativistic quark model SHO wavefunctions to evaluate these amplitudes, and quote numerical results for all amplitudes present in each decay mode. We also discuss the status of the associated experimental candidates, and note which states and decay modes would be especially interesting for future experimental study at hadronic, e+e- and photoproduction facilities. These results should also be useful in distinguishing conventional quark model mesons from exotica such as glueballs and hybrids through their strong decays.Comment: 69 pages, 5 figures, 39 table

The rho -> gamma pi and omega -> gamma pi decays in quark-model approach and estimation of coupling for pion emission by quark

In the framework of the relativistic and gauge invariant spectral integral technique, we calculate radiative decays rho(770)-> gamma pi(140) and omega(780)-> gamma pi(140) supposing all mesons (pi, rho and omega) to be quark-antiquark states. The q anti-q wave functions found for mesons and photon lead to a reasonably good description of data ($\Gamma^{(exp)}_{\rho^{\pm} \to\gamma\pi^{\pm}}=68\pm 30$ keV, $\Gamma^{(exp)}_{\rho^{0}\to\gamma\pi^0}=77\pm 28$ keV, $\Gamma^{(exp)}_{\omega\to\gamma\pi^0}=776\pm 45$ keV) that makes it possible to estimate the coupling for the bremsstrahlung emission of pion by quarks $g_\pi\equiv g_\pi (u\to d \pi)$. We have found two values for the pion bremsstrahlung coupling: $|g_\pi|=16.7 \pm 0.3 ^{+0.1}_{-2.3}$ (Solution I) and $|g_\pi|=3.0 \pm 0.3 ^{+0.1}_{-2.1}$ (Solution II). Within SU(6)-symmetry for nucleons, Solution I gives us for pi NN coupling the value $16.4 \le g_{\pi NN}^2/(4\pi) \le 23.2$ that is in qualitative agreement with the pi N scattering data, $g_{\pi NN}^2/(4\pi)\simeq 14$. For excited states, we have estimated the partial widths in Solution I as follows: $\Gamma (\rho_{2S}^\pm\to \gamma\pi)\simeq 10 - 130$ keV, $\Gamma (\rho_{2S}^0\to \gamma\pi)\simeq 10 -130$ keV, $\Gamma (\omega_{2S}\to \gamma\pi)\simeq 60 - 1080$ keV. The large uncertainties emphasise the necessity to carry out measurements of the meson radiative processes in the region of large masses.Comment: 23 pages in IOP forma

Determination of V_cb from exclusive decays in a relativistic quark model

In the framework of a relativistic covariant Bethe-Salpeter model for the quark-antiquark system we present a renewed determination of the Cabbibo-Kobayashi-Maskawa matrix element $|V_{cb}|$. Complementing an earlier analysis applied to the whole decay spectrum for $B\to D^* e\nu$ we now also employ the ``zero-recoil method'' that uses the end point of the decay spectrum ($\omega=1$) and is suited for heavy-to-heavy transitions. The averaged experimental value extracted from the data at zero recoil, $|V_{cb}|{\cal F}(\omega=1)=0.0343\pm0.0015$, then leads to $|V_{cb}|=0.0360\pm 0.0016$. This value is somewhat larger than the one that uses the whole decay spectrum for the model analysis. We also contrast this result to a nonrelativistic model and to recent experiments on the $B\to D e\nu$ semileptonic decay.Comment: 7 pages, 4 figures, RevTe