Determination of the magnetic susceptibility of the quark condensate using radiative heavy meson decays

We use a light-cone sum rule (LCSR) analysis of the branching ratios of radiative meson decays to contrain the value of the magnetic susceptibility of the quark condensate $\chi(\mu)$. For the first time, we use a complete set of three-particle distribution amplitudes that enables us to give a consistent prediction for the branching ratios. Furthermore we will make use of a very recent update of several non-perturbative parameters. Our final result for $\chi(\mu= 1 {\rm GeV})= 2.85 \pm 0.5 {\rm GeV}^{-2}$ (assuming asymptotic wave functions) agrees with the currently used value of $3.15 \pm 0.3 {\rm GeV}^{-2}$.Comment: 21 pages, 4 figures, references adde

QCD sum rules with finite masses

The concept of QCD sum rules is extended to bound states composed of particles with finite mass such as scalar quarks or strange quarks. It turns out that mass corrections become important in this context. The number of relevant corrections is analyzed in a systematic discussion of the IR- and UV-divergencies, leading in general to a finite number of corrections. The results are demonstrated for a system of two massless quarks and two heavy scalar quarks.Comment: 15 pages, including two pictures to be found in an extra file. Latex neads epsf.st

Twist-3 Distribute Amplitude of the Pion in QCD Sum Rules

We apply the background field method to calculate the moments of the pion two-particles twist-3 distribution amplitude (DA) $\phi_p(\xi)$ in QCD sum rules. In this paper,we do not use the equation of motion for the quarks inside the pion since they are not on shell and introduce a new parameter $m_0^p$ to be determined. We get the parameter $m_0^p\approx1.30GeV$ in this approach. If assuming the expansion of $\phi_p(\xi)$ in the series in Gegenbauer polynomials $C_n^{1/2}(\xi)$, one can obtain its approximate expression which can be determined by its first few moments.Comment: 12 pages, 3 figure

On Possible Light-Torsion Mixing in Background Magnetic Field

The interaction of the light with propagating axial torsion fields in the presence of an external magnetic field has been investigated. Axial torsion fields appearing in higher derivative quantum gravity possess two states, with spin one and zero, with different masses. The torsion field with spin-0 state is a ghost that can be removed if its mass is infinite. We investigate the possibility when the light mixes with the torsion fields resulting in the effect of vacuum birefringence and dichroism. The expressions for ellipticity and the rotation of light polarization axis depending on the coupling constant and the external magnetic field have been obtained.Comment: 12 pages, title changed, shortened journal version, accepted in Eur.Phys.J.

D∗DπD^*D\pi and B∗BπB^*B\pi couplings in QCD

We calculate the $D^*D\pi$ and $B^*B\pi$ couplings using QCD sum rules on the light-cone. In this approach, the large-distance dynamics is incorporated in a set of pion wave functions. We take into account two-particle and three-particle wave functions of twist 2, 3 and 4. The resulting values of the coupling constants are $g_{D^*D\pi}= 12.5\pm 1$ and $g_{B^*B\pi}= 29\pm 3$. From this we predict the partial width \Gamma (D^{*+} \ra D^0 \pi^+ )=32 \pm 5~ keV . We also discuss the soft-pion limit of the sum rules which is equivalent to the external axial field approach employed in earlier calculations. Furthermore, using $g_{B^*B\pi}$ and $g_{D^*D\pi}$ the pole dominance model for the B \ra \pi and D\ra \pi semileptonic form factors is compared with the direct calculation of these form factors in the same framework of light-cone sum rules.Comment: 27 pages (LATEX) +3 figures enclosed as .uu file MPI-PhT/94-62 , CEBAF-TH-94-22, LMU 15/9

Interaction of the single-particle and collective degrees of freedom in non-magic nuclei: the role of phonon tadpole terms

A method of a consistent consideration of the phonon contributions to mass and gap operators in non-magic nuclei is developed in the so-called g^2 approximation, where g is the low-lying phonon creation amplitude. It includes simultaneous accounting for both the usual non-local terms and the phonon tadpole ones. The relations which allow the tadpoles to be calculated without any new parameters are derived. As an application of the results, the role of the phonon tadpoles in the single-particle strength distribution and in the single-particle energies and gap values has been considered. Relation to the problem of the surface nature of pairing is discussed.Comment: 22 pages, 7 figure

Biomorphic SiC from peas and beans

Biomorphic porous SiC ceramics produced by impregnation with liquid or vapor silicon of carbon matrices derived from peas (Pisum sativum L.) and beans (Phaseolus) precursors were investigated. Optical and scanning electron microscopy was used to study the structure of ceramics. It was shown that SiC ceramics made from endosperm of peas and beans seeds has inherited the alveolate structure and possesses many hierarchical pores with diameters varying between 20 to 100 µm. Raman spectroscopy investigations showed that the 3C polytype is formed at a synthesis temperature of about 1550 ⁰C, and that both 3C and 6H-SiC are formed at temperatures of about 1800 ⁰C. It is shown possibilities of production of ceramic articles of various forms from seeds

Изменения структуры и механической прочности кости после пункционной криодеструкции в эксперименте

Purpose of the study — to evaluate possible impact of cryoablation on a healthy bone and to identify probable causes of postoperative fractures.Materials and Methods. The authors performed cryoablation of the femur in the experiment on 8 mature rabbits of Soviet Chinchilla (SC) breed with a follow up for up to two months. Anitrogenous cryoprobe of 1.5 mm in diameter was introduced into the femur through a perforation hole. The bone was completely frozen up to -180°С in two cycles with continuous thermometry. Pathomorfological examinations were performed after 7 and 55 days along with assessment of bone hardness. Preparation of material stipulated sawing the bone at the fracture site along the bone axis. One half-bone was used for histological examination, and another one — for measuring mechanical properties by local pressing of a diamond indenter onto the bone at certain applied force. The distance between measurement points along the bone was 250 μm. Statistical processing included variance significance analysis using t-test.Results. The authors reported bone fractures at the site of cryodestruction in all animals in one week after the procedure. Statistical analysis of the measurements and histological examination demonstrated that freezing of the entire bone diameter up to -180°С results in its complete destruction. Strength reduction around the fracture site corresponded to the temperature distribution area in the range from -9ºС to -15ºС. However, areas of cooling below -40ºС exhibited some bone segments with normal hardness. Mosaic pattern of strength reduction is explained by microcirculation disorders. Histology confirmed thrombosis of intraosseous blood vessels in the area of cryotherapy. The first focal signs of osteomalacia emerged by the end of the first week after cryoablation. Subsequently, the bone preserved its regenerative properties, but by the end of the second month after the procedure the histogenesis was still not completed and the bone did not regain its strength.Conclusion. The authors believe that a limited number of cases, the specific features of the angioarchitecture of animal bones and their ability to produce a heavy periosteal response do not allow to apply obtained quantitative outcomes of the present study to clinical situations. However, complete freezing of the entire bone diameter inevitably results in fracture formation.Цель исследования — выявление возможных последствий криогенной обработки здоровой части кости и вероятных причин возникновения послеоперационных переломов.Материал и методы. Материалом для экспериментального исследования послужили бедренные кости 8 взрослых кроликов породы советская шиншилла. В бедренную кость через перфорационное отверстие вводили азотный криозонд диаметром 1,5 мм. Кость полностью промораживали до -180ºС в двух циклах с непрерывной термометрией. Через 7 и 55 дней выполняли патоморфологические исследования и определяли твердость кости. Подготовка препаратов включала распиливание кости в месте перелома вдоль оси. Одна половина направлялась на гистологическое исследование, вторая подвергалась измерению механической прочности путем локального вдавливания алмазного индентора в кость под действием определенной силы. Расстояние между точками измерения вдоль кости составляло 250 мкм. Статистическая обработка включала вариационный анализ с использованием критерия Стьюдента для определения значимости различий.Результаты. У всех животных через неделю возникли переломы кости в месте криодеструкции. Статистический анализ результатов измерений и гистологическое исследование показал, что охлаждение до -180ºС с замораживанием всего диаметра кости вызывает ее полное разрушение. Снижение прочности вокруг места перелома соответствовало зоне температурного распределения в диапазоне от -9ºС до -15ºС. Однако при этом в зоне охлаждения ниже -40ºС выявлялись участки кости с нормальной твердостью. Мозаичность снижения прочности объяснялась нарушением микроциркуляции. Гистологические исследования выявили тромбоз внутрикостных кровеносных сосудов в зоне криовоздействия. Первые очаговые признаки остеомаляции появлялись к концу первой недели после криоаблации. В дальнейшем кость сохраняла способность к регенерации, но к концу второго месяца гистогенез еще не завершался, кость не восстанавливала свою прочность.Заключение. Ограниченное число наблюдений, видовые особенности ангиоархитектоники кости животных и их способность к образованию мощной периостальной реакции не позволяют переносить количественные результаты исследования на клинические ситуации. Однако образование перелома оказывается неизбежным в случае полного промораживания всего диаметра кости

Strong Couplings of Heavy Mesons to A Light Vector Meson in QCD

We make a detailed analysis of the $BB\rho(DD\rho)$ and $B^*B\rho(D^{*}D\rho)$ strong couplings $g_{BB\rho}(g_{DD\rho})$ and $g_{B^*B\rho}(g_{D^{*}D\rho})$ using QCD light cone sum rules(LCSR). The existing some negligence is pointed out in the previous LCSR calculation on $g_{B^*B\rho} (g_{D^{\ast}D\rho}$) and an updated estimate is presented. Our findings can be used to understand the behavior of the $B,D \to \rho$ semileptonic form factors at large momentum transitions.Comment: 15 pages, latex, 2 figures, version appearing in PRD, typos correcte

Radiative B∗→BγB^{*}\to B\gamma and D∗→DγD^{*}\to D\gamma decays in light cone QCD sum rules

The radiative decays $B^{*} (D^{*})\rightarrow B(D) \gamma$ are investigated in the framework of light cone QCD sum rules. The transition amplitude and decay rates are estimated.It is shown that our results on branching ratios of D meson decays are in good agreement with the existing experimental data.Comment: 13 pages, Latex, 3 figure