Heavy-to-light transition form factors and their relations in light-cone QCD sum rules

The improved light-cone QCD sum rules by using chiral current correlator is systematically reviewed and applied to the calculation of all the heavy-to-light form factors, including all the semileptonic and penguin ones. By choosing suitable chiral currents, the light-cone sum rules for all the form factors are greatly simplified and depend mainly on one leading twist distribution amplitude of the light meson. As a result, relations between these form factors arise naturally. At the considered accuracy these relations reproduce the results obtained in the literature. Moreover, since the explicit dependence on the leading twist distribution amplitudes is preserved, these relations may be more useful to simulate the experimental data and extract the information on the distribution amplitude.Comment: 1+16 pages, no figure

Lepton polarization correlations in B→K∗τ−τ+B \to K^* \tau^- \tau^+

In this work we will study the polarizations of both leptons ($\tau$) in the decay channel $B\to K^* \tau^- \tau^+$. In the case of the dileptonic inclusive decay $B\to K^* \ell^- \ell^+$, where apart from the polarization asymmetries of single lepton $\ell$, one can also observe the polarization asymmetries of both leptons simultaneously. If this sort of measurement is possible then we can have, apart from decay rate, FB asymmetry and the six single lepton polarization asymmetries (three each for $\ell^-$ and $\ell^+$), nine more double polarization asymmetries. This will give us a very useful tool in more strict testing of SM and the physics beyond. We discuss the double polarization asymmetries of $\tau$ leptons in the decay mode $B\to K^* \tau^- \tau^+$ within the SM and the Minimal Supersymmetric extensions of it.Comment: 21 pages, 21 figures; version to match paper to appear in PR

Semileptonic Bs ->DsJ(2460)l nu decay in QCD

Using three point QCD sum rules method, the form factors relevant to the semileptonic Bs ->DsJ (2460)l nu decay are calculated. The q2 dependence of these form factors is evaluated and compared with the heavy quark effective theory predictions. The dependence of the asymmetry parameter alpha, characterizing the polarization of DsJ meson, on q2 is studied .The branching ratio of this decay is also estimated and is shown that it can be easily detected at LHC.Comment: 21 pages, 5 figures and 1 Tabl

Thermal-Mechanical Properties of Polyurethane-Clay Shape Memory Polymer Nanocomposites

Shape memory nanocomposites of polyurethane (PU)-clay were fabricated by melt mixing of PU and nano-clay. Based on nano-indentation and microhardness tests, the strength of the nanocomposites increased dramatically as a function of clay content, which is attributed to the enhanced nanoclay–polymer interactions. Thermal mechanical experiments demonstrated good mechanical and shape memory effects of the nanocomposites. Full shape memory recovery was displayed by both the pure PU and PU-clay nanocomposites.

QCD sum rules analysis of the rare B_c \rar X\nu\bar{\nu} decays

Taking into account the gluon correction contributions to the correlation function, the form factors relevant to the rare B_c \rar X \nu\bar{\nu} decays are calculated in the framework of the three point QCD sum rules, where $X$ stands for axial vector particle, $AV(D_{s1})$, and vector particles, $V(D^*,D^*_s)$. The total decay width as well as the branching ratio of these decays are evaluated using the $q^2$ dependent expressions of the form factors. A comparison of our results with the predictions of the relativistic constituent quark model is presented.Comment: 21 Pages, 2 Figures and 5 Table

General analysis of the rare Bc->D^*_s l^+ l^- decay beyond the standard model

The general analysis of the rare Bc->D^*_s l^+ l^- decay is presented by using the most general, model independent effective Hamiltonian. The dependencies of the branching ratios, longitudinal, normal and transversal polarization asymmetries for l^- and the combined asymmetries for l^- and l^+ on the new Wilson coefficients are investigated. Our analysis shows that the lepton polarization asymmetries are very sensitive to the scalar and tensor type interactions, which will be very useful in looking for new physics beyond the standard model.Comment: 27 Pages, 14 Figure

Structural and Magnetic Properties of Pyrochlore Solid Solutions (Y,Lu)2Ti2-x(Nb,Ta)xO7+/-y

The synthesis and characterization of the pyrochlore solid solutions, Y2Ti2-xNbxO7-y, Lu2Ti2-xNbxO7-y, Y2Ti2-xTaxO7-y and Lu2TiTaO7-y (-0.4<y<0.5), is described. Synthesis at 1600 C, and 10-5 Torr yields oxygen deficiency in all systems. All compounds are found to be paramagnetic and semiconducting, with the size of the local moments being less, in some cases substantially less, than the expected value for the number of nominally unpaired electrons present. Thermogravimetric analysis (TGA) shows that all compounds can be fully oxidized while retaining the pyrochlore structure, yielding oxygen rich pyrochlores as white powders. Powder neutron diffraction of Y2TiNbO7-based samples was done. Refinement of the data for oxygen deficient Y2TiNbO6.76 indicates the presence of a distribution of oxygen over the 8b and 48f sites. Refinement of the data for oxygen rich Y2TiNbO7.5 shows these sites to be completely filled, with an additional half filling of the 8a site. The magnetic and TGA data strongly suggest a preference for a Ti3+/(Nb,Ta)5+ combination, as opposed to Ti4+/(Nb,Ta)4+, in this pyrochlore family. In addition, the evidence clearly points to Ti3+ as the source of the localized moments, with no evidence for localized Nb4+ moments.Comment: Accepted to Journal of Solid State Chemistr

Polarized Dirac fermions in de Sitter spacetime

The tetrad gauge invariant theory of the free Dirac field in two special moving charts of the de Sitter spacetime is investigated pointing out the operators that commute with the Dirac one. These are the generators of the symmetry transformations corresponding to isometries that give rise to conserved quantities according to the Noether theorem. With their help the plane wave spinor solutions of the Dirac equation with given momentum and helicity are derived and the final form of the quantum Dirac field is established. It is shown that the canonical quantization leads to a correct physical interpretation of the massive or massless fermion quantum fields.Comment: 19 pages, LaTeX w AMS sym

Propiedades antioxidantes de dos nuevos derivados lipofílicos del ácido gálico

The effectiveness of two lipophilic derivatives of the natural phenol, gallic acid (GA), synthesized using methyl gallate as starting material was investigated. The antioxidant activities of these novel phenolics compared to GA,&nbsp;tert-butylhydroquinone (TBHQ) and butylated hydroxytoluene (BHT) were evaluated in bulk oil, emulsion and the DPPH systems. The results showed that the new compounds effectively delayed lipid oxidation much better than GA and other antioxidants under Rancimat (100-140 °C) and emulsion tests. In the bulk oil system at 65 °C, they still behaved better than GA, but TBHQ had the highest activity. Thus, replacing the electron-withdrawing carboxylic group on GA by covalently linking sterically hindered phenols to its phenyl ring increased its lipophilicity and also resulted in synergistic effects which improved overall antioxidant activity through stabilization of the phenoxy radical. These new antioxidant variants satisfy industrial demands for bioactive ingredients with strong antioxidant potentials under different food processing conditions.Se aporta información sobre de la eficacia de dos derivados lipofílicos de fenoles naturales derivados del ácido gálico (GA) y sintetizados utilizando galato de metilo como material de partida. Las actividades antioxidantes de estos nuevos compuestos fenólicos en comparación con el GA, terc-butilhidroquinona (TBHQ) y butil hidroxitolueno (BHT) se evaluaron en aceites, sistemas emulsionados y mediante DPPH. Los resultados mostraron que los nuevos compuestos retrasaron efectivamente la oxidación de lípidos mucho más fuerte que el GA y otros antioxidantes mediante Rancimat (100-140 °C) y pruebas de emulsión. En el aceite a 65 °C, se comportaron mejor que el GA, pero el TBHQ tuvo la actividad más alta. Por lo tanto, reemplazar el grupo carboxílico en GA al unir covalentemente fenoles impedidos estéricamente a su anillo de fenilo ayudó a aumentar su lipofilia y también dio como resultado efectos sinérgicos que mejoraron la actividad antioxidante general a través de la estabilización del radical fenoxi. Estas nuevas variantes de antioxidantes satisfacen la demanda industrial de ingredientes bioactivos con un fuerte potencial antioxidante en diferentes condiciones de procesamiento de alimentos

Light-cone QCD Sum Rules for the Λ\Lambda Baryon Electromagnetic Form Factors and its magnetic moment

We present the light-cone QCD sum rules up to twist 6 for the electromagnetic form factors of the $\Lambda$ baryon. To estimate the magnetic moment of the baryon, the magnetic form factor is fitted by the dipole formula. The numerical value of our estimation is $\mu_\Lambda=-(0.64\pm0.04)\mu_N$, which is in accordance with the experimental data and the existing theoretical results. We find that it is twist 4 but not the leading twist distribution amplitudes that dominate the results.Comment: 13 page, 7 figures, accepted for publication in Euro. Phys. J.