Dynamics of strong and radiative decays of D_s-mesons in the hadrogenesis conjecture

The positive parity scalar D ＊ s0 （2317） and axial-vector D ＊ s1 （2460） charmed strange mesons are generated by coupled-channel dynamics through the s-wave scattering of Goldstone bosons off the pseudoscalar and vector D（D s ）-meson ground states.The specific masses of these states are obtained as a consequence of the attraction arising from the Weinberg-Tomozawa interaction in the chiral Lagrangian.Chiral corrections to order Q 2 χ are calculated and found to be small.The D ＊ s0 （2317） and D ＊ s1 （2460） mesons decay either strongly into the isospin-violating π 0 D s and π 0 D ？ s channels or electromagnetically.We show that the π 0-η and （K^ 0 D ^＋-K^ ＋ D^ 0 ） mixings act constructively to generate strong widths of the order of 140 keV and emphasize the sensitivity of this value to the KD component of the states.The one-loop contribution to the radiative decay amplitudes of scalar and axial-vector states is calculated using the electromagnetic Lagrangian to chiral order Q 2 χ .We show the importance of taking into account processes involving light vector mesons explicitly in the dynamics of electromagnetic decays.The radiative width are sensitive to both η D s and KD components,hence providing information complementary to the strong widths on the positive parity D s-meson structure.     

Direct pion emission in D*~+→D~+π decays

The QCD multipole expansion(QCDME) is based on quantum field theory and has been extensively applied to study transitions among Υ and ψ family members. As it refers to non-perturbative QCD, however, it has only a certain application range. Even though it successfully explains the transition data among members of the Υ(ψ) family, as Eichten indicates, beyond the production threshold of mediate states it fails to match data by several orders of magnitude. In this work, by studying a simple decay mode D*→D +π~0, where a pion may be emitted before D* transitions into D, we analyze the contribution of QCD multipole expansion. As the Dπ portal is open,the dominant contribution is an OZI-allowed process where a light quark-pair is excited out from vacuum, and its contribution can be evaluated by the ~3P_0 model. Since direct pion emission is OZI-suppressed and violates isospin conservation, its contribution must be much smaller than the dominant one. By a careful calculation, we estimate that the QCDME contribution should be 3–4 orders smaller than the dominant contribution and this result can offer a quantitative interpretation for Eichten's statement.     

Phenomenology of neutral D-meson decays and double-flavour oscillations

Decays of neutral D-mesons are considered phenomenologically without invoking any particular models. Special attention is given to cascade decays with intermediate neutral kaons where coherent double-flavour oscillations (CDFO) become possible. We show necessity and unique possibilities of experiments on CDFO. They allow to relate with each other widths and masses of D-meson eigenstates, to separate interference effects due to D ⁰-ˉD ⁰ mixing and/or Cabibbo-favoured vs. doubly-suppressed transitions. Such experiments provide the only known ways to unambiguous model-independent measurements of all CP-violating parameters and of Cabibbo-doubly-suppressed amplitudes, where the New Physics may have more prominent manifestations. Similar experiments would be useful and interesting also for charged D-meson decays to neutral kaons. Received: 13 August 1998     

Meson loops in the f0(980) and a0(980) radiative decays into ρ , ω

We calculate the radiative decay widths of the a ₀(980) and f ₀(980) scalar mesons into ργ and ωγ considering the dynamically generated nature of these scalar resonances within the realm of the chiral unitary approach. The main ingredient in the evaluation of the radiative width of the scalar mesons are the loops coming from the decay into their constituent pseudoscalar-pseudoscalar components and the subsequent radiation of the photon. The dominant diagrams with only pseudoscalar mesons in the loops are found to be convergent while the divergence of those with a vector meson in the loop are written in terms of the two-meson loop function easily regularizable. We provide results for all the possible charge channels and obtain results, with uncertainties, which differ significantly from quark loops models and some version of vector meson dominance.     

D0-(D-)0 mixing and other charm decays at Belle

The D0-D-0 mixing at Belle in different modes with corresponding methods is reported in this paper,there is a clear evidence for non-zero y D0 mixing parameter,and the measurement of D0 mixing parameter x is still a challenge.CP violation in the decays is not observed.Branching fractions of other charm decays are presented.     

Study of semileptonic and nonleptonic decays of the B<Subscript>c</Subscript><Superscript>-</Superscript> meson

We evaluate semileptonic and two-meson nonleptonic decays of the B _c ^- meson in the framework of a nonrelativistic quark model. The former are done in spectator approximation using one-body current operators at the quark level. Our model reproduces the constraints of heavy-quark spin symmetry obtained in the limit of infinite heavy-quark mass. For the two-meson nonleptonic decays we work in factorization approximation. We compare our results to the ones obtained in different relativistic approaches.     

Chiral SU(4) × SU(4) breaking: masses and decay constants of charmed hadrons

The (4, 4*) ⊕ (4*, 4) model of broken chiral SU (4) × SU (4) symmetry has been used to calculate the third-order coupling constants involving charmed and ordinary pseudoscalar mesons. These coupling constants are exploited to derive some interesting new relations among the masses and decay constants of these charmed particles. Using the known masses and decay constants as inputs, we exploit these relations to predict:F _D = −1·41F _π ,F _F = −1·13F _π ,F _D/F_F = 1·25,m(D _s) = 1·43 GeV,m(F _s) = 1·39 GeV andm(K _s) = 1·02 GeV.     

Study a0(980)-f0(980)mixing in charmonium decays

In this proceeding,we propose to directly measure the a00(980)-f0(980)mixing in J/ψ→φ f0(980)φa00(980)and χc1 →π0a00(980)→π0f0(980)with the upgraded Beijing Electron Positron Collider(BEPCII)with BESⅢ detector.We show that a narrow peak of about 8 MeV will be produced by the a00(980)-f0(980)mixing,and the predominant feature makes it standing out from the background contributions.The predicted branching ratios for these two reactions are both expected to be about O(10-6),which is unambiguously accessible with109 J/ψ and 3 × 108 χc1 at BESⅢ.     

Continuous wavelength tuning of InAs quantum dots on InP (1 0 0) and (3 1 1)A substrates by chemical-beam epitaxy

The growth of InAs quantum dots (QDs) on InP (1 0 0) and (3 1 1)A substrates by chemical-beam epitaxy is studied. The InAs QDs are embedded in a GaInAsP layer lattice-matched to InP. We demonstrate an effective way to continuously tune the emission wavelength of InAs QDs grown on InP (1 0 0). With an ultra-thin GaAs layer inserted between the QD layer and the GaInAsP buffer, the peak wavelength from the InAs QDs can be continuously tuned from above 1.6 μm down to 1.5 μm at room temperature. The major role of the thin GaAs layer is to greatly suppress the As/P exchange during the deposition of InAs and subsequent growth interruption under arsenic flux, as well as to consume the segregated In layer floating on the GaInAsP buffer. Moreover, it is found that InP (3 1 1)A substrates are particularly promising for formation of uniform InAs QDs. The growth of InAs on InP (3 1 1)A consists of two stages: nanowire formation due to strain-driven growth instability and subsequent QD formation on top of the wires. The excellent size uniformity of the InAs QDs obtained on InP (3 1 1)A manifests itself in the narrow photoluminescence line width of 26 meV at 4.8 K.     

Study of single crystal surfaces with polarized 8Li

NMR experiments on ⁸Li adsorbed on semiconductor and metallic surfaces are described (Si(1 1 1)−(7×7) and Ru(0 0 1)). They yield detailed information on LDOS (E_F), the local density of states at the nucleus and at Fermi energy. This revised version was published online in August 2006 with corrections to the Cover Date.     

The effect of phonon anisotropic scattering on the thermal conductivity of silicon thin films at 300K and 400K

Previous studies have shown that anisotropy in phonon transport exist because of the difference in phonon dispersion relation due to different lattice directions, as observed by a difference in in-plane and cross-plane thermal conductivities. Our current work intends to study the effect of anisotropy scattering on silicon thermal conductivity at 300 K and 400 K. We adopt the Henyey and Greenstein probability density function in our phonon Monte Carlo simulation to investigate the effect of highly forward and backward scattering events. The impact of applying the anisotropy scattering using this approach is discussed in detail. While the forward and backward scattering will increase and decrease thermal conductivity respectively, the extent of the effect is non-linear such that forward scattering has a more obvious effect on thermal conductivity than backward scattering.     

Numerical investigation of the effect of soot aggregation on the radiative properties in the infrared region and radiative heat transfer

The effect of aggregation on soot radiative properties in the infrared region of the spectrum is numerically investigated using Rayleigh-Debye-Gans theory for fractal aggregates (RDG-FA). In order to use the RDG-FA theory for a wide range of aggregate sizes and wavelengths, the predicted phase functions, scattering and absorption coefficients are compared with a more accurate theory, the integral equation formulation for scattering—IEFS. The importance of scattering when compared with absorption is investigated, as well as the effect of aggregation on the phase function shape and on the scattering cross section. It is concluded that in the case of small aggregates formed with small primary particles the scattering coefficient is negligible compared with the absorption coefficient, and scattering and aggregation of primary particles can be ignored. Thus, the Rayleigh approximation can be used leading to isotropic scattering. In the case of large aggregates constituted by large primary particles, aggregation becomes important and the scattering cross section is of the same order of magnitude of the absorption cross section. Moreover, the phase function becomes highly peaked in the forward direction. Therefore, the Rayleigh and the equivalent volume Mie sphere approximations are not valid, and the RDG-FA method emerges as a good compromise between accuracy and simplicity of application. However, radiative transfer calculations between two infinite, parallel, black walls show that scattering may always be neglected in the calculation of total radiative heat source and heat fluxes to the walls. The minor influence of scattering on the accuracy of the predictions is explained by the shift between the spectral region where scattering is important and the region where the spectral radiative heat source is large.     

Si(001)-(2*2*1):H表面O2吸附的密度泛函理论研究

建立了一种计算Si(001)-(2×2×1):H表面O2吸附的理论模型．在周期性边界条件下,采用基于密度泛函理论广义梯度近似的超软赝势法对Si(001)-(2×2×1):H表面O2吸附进行了第一性研究．通过占位能的计算,得到了Si(001)-(2×2×1):H表面O2的最佳吸附位置．计算结果表明吸附后的反应产物应为Si=O和H2O,从理论上支持了D．Kovalev等人提出反应机制．     

(1+2)维强非局域空间光孤子的相互作用

强非局域空间光孤子是指满足强非局域条件的空间孤子.在Snyder和Mitchell工作的基础上，获得了不共面对称斜入射(1+2)维强非局域空间光孤子对相互作用问题的精确解析解.结果表明，光束初始中心距离在大范围尺度内变化时，双孤子的演化都能形成类似DNA结构的稳定缠绕，这种稳定缠绕的结构与双孤子的初始相位差无关；光束中心在横截面上的投影轨迹一般是一个斜椭圆，通过改变两光束的初始中心距离和倾斜度可以控制该椭圆轨迹的变化.指出了利用(1+2)维强非局域空间光孤子的相互作用特性实现平面全光开关和全光互联的潜在可能性. 关键词： (1+2)维非局域非线性介质 空间光孤子的相互作用 全光开关 全光互联     

Adsorption and reaction of methanethiol on the Ru(0 0 0 1)-p(2 × 2)O surface: A TPD and XPS study

Methanethiol adsorbed on Ru(0 0 0 1)-p(2 × 2)O has been studied by TPD and XPS. The dissociation of methanethiol to methylthiolate and hydrogen at 90 K is evidenced by the observation of hydroxyl and water. The saturation coverage of methylthiolate is ∼0.15 ML, measured by both XPS and TPD. A detailed analysis suggests that only the hcp-hollow sites have been occupied. Upon annealing the surface, water and hydroxyl desorb from the surface at ∼210 K. Methylthiolate decomposes to methyl radical and atomic sulphur via C-S cleavage between 350 and 450 K. Some methyl radicals (0.05 ML) have been transferred to Ru atoms before they decompose to carbon and hydrogen. The rest of methyl radicals desorb as gaseous phase. No evidence for the transfer of methyl radical to surface oxygen has been found.     

Pressure Effect on Solvation Dynamics and Rotational Dynamics in Solution

Effects of pressure on solvation dynamics and rotational dynamics in solution were studied by picosecond time-dependent fluorescence Stokes shift (TDFSS) and picosecond time-dependent fluorescence rotational depolarization (TDFRD). The fluorescence lifetimes of solute probes, coumarin 153 and p -terphenyl, in various solvents were measured at high pressures by time-correlated single photon counting (TCSPC) technique with time resolution of 20-30 ps.     

The semileptonic form factors of B and D mesons in the Quark Confinement Model

The form factors of the weak currents, which appear in the semileptonic decays of the heavy pseudoscalar mesons are calculated within the quark confinement model by taking into account, for the first time, the structure of heavy-meson vertex and the finite quark mass contribution in the heavy-quark propagators. The results are in quite good agreement with the experimental data. Received: 9 June 2000 / Accepted: 15 August 2000