Energy Gap from Tunneling and Metallic Sharvin Contacts onto MgB2: Evidence for a Weakened Surface Layer

Point-contact tunnel junctions using a Au tip on sintered MgB2 pellets reveal a sharp superconducting energy gap that is confirmed by subsequent metallic Sharvin contacts made on the same sample. The peak in the tunneling conductance and the Sharvin contact conductance follow the BCS form, but the gap values of 4.3 meV are less than the weak-coupling BCS value of 5.9 meV for the bulk Tc of 39 K. The low value of Delta compared to the BCS value for the bulk Tc is possibly due to chemical reactions at the surface.Comment: 3 pages, 3 figure

Multibeam Maser Survey of methanol and excited OH in the Magellanic clouds: new detections and maser abundance estimates

‘The definitive version is available at www.blackwell-synergy.com.’ Copyright Blackwell Publishing DOI: 10.1111/j.1365-2966.2008.12888.xPeer reviewe

Supersymmetric predictions for the inclusive b→sγb\to s\gamma decay

We study the penguin induced transition $b\to s\ \gamma$ in the minimal N=1 supersymmetric extension of the Standard Model with radiative breaking of the electroweak group. We include the effects of one-loop corrections to the Higgs potential and scalar masses. We show that the present upper and lower experimental limits on the inclusive decay sharply constrain the parameter space of the model in a wide range of $\tan\beta$ values. The implications of the recently advocated relation $|B|\ge 2$ for the bilinear SUSY soft breaking parameter in grand unified theories are also analyzed.Comment: 23 pages + 12 figures (hardcopies available on request), LATEX, SISSA 40/94/E

Implications of the Top Quark Mass Measurement for the CKM Parameters, xsx_s and CP Asymmetries

Motivated by the recent determination of the top quark mass by the CDF collaboration, \mt =174 \pm 10 ^{+13}_{-12} GeV, we review and update the constraints on the parameters of the quark flavour mixing matrix $V_{CKM}$ in the standard model. In performing our fits, we use inputs from the measurements of the following quantities: (i) \abseps, the CP-violating parameter in $K$ decays, (ii) \delmd, the mass difference due to the \bdbdbar\ mixing, (iii) the matrix elements \absvcb and \absvub, and (iv) $B$-hadron lifetimes. We find that the allowed region of the unitarity triangle is very large, mostly due to theoretical uncertainties. (This emphasizes the importance of measurements of CP-violating rate asymmetries in the $B$ system.) Nevertheless, the present data do somewhat restrict the allowed values of the coupling constant product $f_{B_d}\sqrt{\hat{B}_{B_d}}$ and the renormalization-scale invariant bag constant $\hat{B}_K$. With the updated CKM matrix we present the currently-allowed range of the ratio $\vert V_{td}/V_{ts} \vert$, as well as the standard model predictions for the \bsbsbar\ mixing parameter \xs and the quantities $\sin 2\alpha$, $\sin 2\beta$ and $\sin^2\gamma$, which characterize the CP-asymmetries in $B$-decays. The ALEPH collaboration has recently reported a significant improvement on the lower limit on the \bs-\bsb mass difference, $\Delta M_s/\Delta M_d > 11.3$ (95\% C.L.). This has interesting consequences for the CKM parameters which are also worked out. NOTE: this is a revised and updated version of our previous paper.Comment: LaTeX, 27 pages, 16 uuencoded figures (enclosed), CERN-TH.7398/94, UdeM-GPP-TH-94-0

Associated production of charged Higgs bosons and top quarks with POWHEG

The associated production of charged Higgs bosons and top quarks at hadron colliders is an important discovery channel to establish the existence of a non-minimal Higgs sector. Here, we present details of a next-to-leading order (NLO) calculation of this process using the Catani-Seymour dipole formalism and describe its implementation in POWHEG, which allows to match NLO calculations to parton showers. Numerical predictions are presented using the PYTHIA parton shower and are compared to those obtained previously at fixed order, to a leading order calculation matched to the PYTHIA parton shower, and to a different NLO calculation matched to the HERWIG parton shower with MC@NLO. We also present numerical predictions and theoretical uncertainties for various Two Higgs Doublet Models at the Tevatron and LHC.Comment: 36 page

Evaluation of the possibility of using diatomite natural mineral as a composite agent in acrylic coating

WOS: 000427736200014In the present study the possibility of the commercially available acryl and diatomite earth (DE) mineral as a composite coating for corrosion protection of Mg alloys has been evaluated. The acrylic coating is used as a top coating in a wide field of applications like automotive, aerospace, medicine and electronics where it shows beneficial properties. Diatomite-dispersed acrylic paint was applied over the substrate by conventional spray technique with an air pressure of 3 kg cm(-2). Firstly the acryl was mixed with hardener and then the DE was added to the mixture. Four types of coating with 0, 2, 4, 8 g/L DE have been prepared. The results show that adding up to 4 g/L of the DE improved the corrosion resistance and produced a coating with acceptable surface roughness

Production and Decay of D_1(2420)^0 and D_2^*(2460)^0

We have investigated $D^{+}\pi^{-}$ and $D^{*+}\pi^{-}$ final states and observed the two established $L=1$ charmed mesons, the $D_1(2420)^0$ with mass $2421^{+1+2}_{-2-2}$ MeV/c$^{2}$ and width $20^{+6+3}_{-5-3}$ MeV/c$^{2}$ and the $D_2^*(2460)^0$ with mass $2465 \pm 3 \pm 3$ MeV/c$^{2}$ and width $28^{+8+6}_{-7-6}$ MeV/c$^{2}$. Properties of these final states, including their decay angular distributions and spin-parity assignments, have been studied. We identify these two mesons as the $j_{light}=3/2$ doublet predicted by HQET. We also obtain constraints on {\footnotesize $\Gamma_S/(\Gamma_S + \Gamma_D)$} as a function of the cosine of the relative phase of the two amplitudes in the $D_1(2420)^0$ decay.Comment: 15 pages in REVTEX format. hardcopies with figures can be obtained by sending mail to: [email protected]