Pion-induced ${K}^{* }$ production with ${{\rm{\Sigma }}}^{* }$ baryon off proton target

In this work, the reaction ${\pi }^{-}p\to {K}^{* }{{\rm{\Sigma }}}^{* }$ is investigated with an effective Lagrangian approach. The contributions from the Born terms, including the s, t, and u channel, are considered, and the Regge model and the Feynman model are applied to treat the t -channel contribution. The existing experimental data can be reproduced with the best-fitted χ ² being 2.38 and 1.54 for the Feynman and Regge models, respectively. Moreover, it is found that the contribution from the t channel is dominant in the cross-section. The contribution of the u channel is mainly distributed at backward angles, and the contribution from the s channel is small and negligible. In the Feynman model, the contribution of the t -channel K exchange is much larger than the contribution of the ${K}^{* }$ exchange, while in the Regge model the contribution of the t -channel K exchange is comparable to that of the ${K}^{* }$ exchange. Prediction about the differential cross-section of the ${\pi }^{-}p\to {K}^{* }{{\rm{\Sigma }}}^{* }$ reaction is also presented, which is helpful for clarifying the role of the Regge treatment. The current results suggest high-precision experimental measurements which can be performed at J-PARC and COMPASS.     

Transportfunktionen von Stickstoff bis 26000 °K

TheE(I)-characteristic and a large number ofT(r, I)-distributions measured in a 5 mm ØN ₂ cascade arc at normal pressure are used to evaluate the transport properties of nitrogen up to 26,000 °K. The electrical conductivityσ(T) and from this the cross-section for atom-electron collision and the Coulomb-cross-section are determined directly from theE(I)- and severalT(r, I)-curves. For the evaluation of the thermal conductivityκ(T) three temperature regions are discerned: Up to about 10,000 °Kκ(T) is derived directly from the energy equation since here the energy transport by radiation does not play an important role. Between 10,000 and 15,000 °K the radiative energy flux for different arc currents, the thermal conductivity and from this the charge exchange cross-section are determined in a good approximation utilizing the large number of measured temperature distributions. Above 15,000 °K the already evaluated collision cross-sections are used to computeκ(T). Withκ(T) known the radial distribution of the balance between emission and absorption of radiative power per unit volume is evaluated for different arc currents. It turns out, that at the highest measured arc current, i.e. 570 A, in the axial region of the arc about 95% of the supplied energy is carried off by radiation.     

分子极性对类胡萝卜素共振拉曼光谱的影响

测量了非极性分子β胡萝卜素和极性分子角黄素, 在非极性溶剂CS₂和极性溶 剂1,2二氯乙烷中243–293 K的温度范围内的共振拉曼光谱. 结果表明, 溶质和溶剂的极性对拉曼光谱影响很大. 非极性分子β胡萝卜素在非极性溶剂CS₂中的拉曼散射截面最大, 线宽最窄, 而极性分子角黄素在极性溶剂1,2二氯乙烷中的拉曼散射截面最小, 线宽最大. 用溶剂效应及线性多烯分子的“相干弱阻尼电子-晶格振动”, “有效共轭长度”模型给予了解释.     

利用实验I(L)/I(K)比值改进薄膜无标样定量分析

利用透射扫描电子显微镜和X射线能谱仪,在入射电压V₀为40,80,100,120,160和200kV下,测定了从Ge到Sn八种元素薄膜的标识X射线强度比值I(L)/I(K),并结合Cliff-Lorimerk_XSi因子和它的内插值,扩充了目前仅有的少数几个L系的Cliff-Lorimer因子。为了确定哪个电离截面Q公式最好,比较了利用九种不同Q公式计算出的I(L)/I(K)和我们的实验值I(L)/I(K)。发现两者之间存在着很大的差别。进一步考虑计算强度公式中各物理参量引起的误差后,我们认为上述差别主要来源于不准确的Q公式,而且和实验值符合最好的Fabredela Ripelle的电离截面也需要进行修正。利用我们修正后的Q公式,在V₀为100和200kV下,分析了几种已知成分的样品并和EDAX的分析结果进行了比较。结果表明:在不同电压下,利用不同线系K—K,K—L,我们分析结果的误差有显著的降低。 关键词：     

Optimized 90° Polarization Shift Step Twists for Ku, K and Ka Bands

Optimized models for 90° polarization shift step twists for Ku, K and Ka bands are presented. The cross-section of the waveguide employed is similar to that of a rectangular one, with the difference that the walls of the shorter side are part of a circular one with the proper diameter. The optimized models have been found using the CST Microwave Studio simulation tool and in all cases the return loss is kept below -20 dB for a wide range of frequency spectrum. Two examples are given, one for Ku band and the other for K and Ka ones.     

Bs-->K(*)0 K(*)0 CP asymmetries: golden channels for new physics searches

We point out that time-dependent CP asymmetries in B_(s)-->K(*0) K[over](*0) decays probe the presence of new physics in b-->s transitions with an unprecedented theoretical accuracy. We show that, contrary to the case of B_(d)-->phiK_(S), it is possible to obtain a model-independent prediction for the coefficient S(B_(s)-->K(*0) K[over](*0)) in the standard model. We give an estimate of the experimental precision achievable with the next generation of B physics experiments. We also discuss how this approach can be extended to the case of B_(s)-->K[over](*0) K(0), B_(s)-->K(*0) K[over](0), and B_(s)-->K(0) K[over](0) decays and the different experimental challenges for these channels.     

Theoretical calculation of electron-impact resonance excitation of alkali atoms

Total cross-section for electron impact excitation of the resonance levels in Li, Na and K are calculated using the method due to Crothers and McCarroll. The results are compared with other available theoretical and experimental data.     

Formation of cross-sections for electron scattering by thermal lattice excitations in stainless steels

We present the results from experimental (in situ) measurements of the electrical resistance and thermal expansion of stainless steels in the temperature range 300–1000 K. Based on a correlation analysis of these properties, the decisive role of the thermal deformation of the atomic lattice in the formation of the electron scattering cross-section is established.     

Thermal conductivity of K0.3MoO3

Measurements of thermal conductivity of the blue bronze K_0.3MoO₃ are reported in the range 90–300K. A large anomaly at 183 K ascribed to the CDW transition and an overall good agreement of the experimental results with the estimations based on the Wiedemann-Franz are found.     

Near threshold photoionization of excited alkali atoms Ak(np) (Ak = Na, K, Rb, Cs; n = 3-6)

The effect of the polarization of the atomic core by the outer electron on near threshold photoionization of excited alkali atoms Ak(np) (Ak = Na-Cs; n=3-6) is investigated. Partial and total cross-sections for photo-ionization of the np-electron were computed utilizing the configuration interaction technique with Pauli-Fock atomic orbitals (CIPF) and including the long range core polarization potential (CP). To calculate the core polarization potential the variational principle is applied. Comparison with previous theoretical results and with available experimental data is made for the total cross-section , for the electron angular distribution parameter , for the ratio of the reduced electric dipole matrix elements and for the phase shift difference , associated with the d-wave and s-wave continua, respectively. In the comparison, new experimental results for , , and , measured for laser-excited, polarized ³⁹K(4p _3/2) atoms, have been included. Received 21 July 1999 and Received in final form 14 October 1999     

Absolute absorption cross-section measurements of Schumann-Runge continuum of O2 at 90 and 295 K

Laboratory measurements of the absorption cross-section of the Schumann-Runge continuum of O₂ at the temperatures 90 and 295 K have been made in the wavelength region 130-175 nm. The absolute absorption cross-sections at the same temperatures have been measured at several discrete wavelengths through the region. The absolute cross-sections of the O₂ continuum have been used to put relative cross-sections on a firm absolute basis throughout the region 130-175 nm. These recalibrated cross-sections are available as numerical compilations.     

2π→2K SCATTERING AND πK ELASTIC SCATTERING

The 2π→2K low energy scattering cross-section was obtained using the relation between field and current. The low energy πK elastic scattering cross-section and its scattering length were also obtained using cross symmetry.     

Photoionization of electrons and holes at oxygen donors in gallium phosphide

The spectral dependence of the photoionization cross-section for the oxygen donor in GaP is studied in the temperature range between 90 and 410°K by steady state photocurrent measurements using two different radiation sources. From a fit of Lucovsky's model to the experimental results, accurate information is obtained about the energy position of the oxygen donor at all temperatures. It is found that the oxygen level is pinned to the valence band for temperatures above 295 K and that at these temperatures the Franck-Condon shift is very small. This may indicate that there is little interaction between the impurity level and the surrounding lattice.     

Single-electron-capture cross sections for 0.4–5.0 keV He+ ions incident on alkali-vapor targets

Total cross sections for single-electron capture by He⁺ ions in vapor targets of Cs, Rb, K and Na have been determined in the energy range 0.4–5.0 keV. The energy dependence of the cross-section curves is very similar for all the targets. The cross sections for all the targets are maximum at about the same energy, 1.5 keV. Comparison is made with other reported experimental and theoretical results.     

Energy and decay width of the πK atom

The energy and the decay width of the πK atom are evaluated in the framework of the quasipotential-constraint theory approach. The main electromagnetic and isospin symmetry breaking corrections to the lowest-order formulas for the energy shift from the Coulomb binding energy and for the decay width are calculated. They are estimated to be of the order of a few per cent. We display formulas to extract the strong interaction S-wave πK scattering lengths from future experimental data concerning the πK atom.PACS 03.65.Pm; 11.10.St; 12.39.Fe; 13.40.Ks     

Radiative lifetime and oscillator strength determinations in potassium ions (K V, K VI and K VII)

Oscillator strengths have been calculated for the transitions depopulating levels of the 3s²3p³, 3s3p⁴ configurations of K V, of the 3s²3p², 3s3p³ configurations of K VI and of the 3s²3p, 3s3p², 3p³ and 3s3p3d configurations of K VII. A multiconfiguration Dirac-Fock method, incorporating the relativistic two-body Breit interaction and quantum electrodynamics corrections due to self-energy and vacuum polarization, has been used for the calculations. The reliability of this approach has been tested by comparison with relativistic Hartree-Fock calculations and also with some experimental measurements performed by beam-foil spectroscopy at a beam energy of 1.7 MeV.     

Energy levels of 37K

Angular distributions have been measured for six ³⁶Ar(p,γ)³⁷K resonances in the E_p = 0.9−3.0 MeV energy region. These experiments yield spin- and parity assignments to seven excited states of ³⁷K, γ-ray branching ratios for each state, together with the multipolarity mixing ratios of most transitions. Lifetimes have been deduced from the same data with the DSA method.Excitation energies have been determined with a precision up to 20 eV. A resonance- and excitation-energy measurement at the E_p = 918keV resonance yields a ³⁶Ar(p, γ)³⁷K Q-value of Q = 1857.57 ± 0.09 keV.The ³⁶Ar(p, p₁γ) yield curve, measured in the E_p = 2.6–3.3 MeV region, yields additional information on resonance and excitation energies of ³⁷K states with a typical precision of 0.6 keV.The new data on ³⁷K levels allow a detailed comparison of the level schemes of the mirror nuclei ³⁷Ar and ³⁷K. The present experimental data agree quite well with the results of previous shell-model calculations.     

Phonon-phonon scattering cross-sections from crossed phonon beams

In two crossed phonon beams generated by heatpulses the attenuation of high frequency phonons by phonon-phonon interaction was observed for the slow transverse phonons of the [1 1 0] branch of Si at 3.6 K. From the experimental data the phonon scattering cross-section for a three phonon normal process can be calculated.     

Observation of B+ --> K0K+ and B0 --> K0K0

We report observations of the b --> d penguin-dominated decays B+ --> K0K+ and B0 --> K0K0 in 316 fb(-1) of e+ e- collision data collected with the BABAR detector. We measure the branching fractions B(B+ --> K0K+) = (1.61+/-0.44+/-0.09) x 10(-6) and B(B0 --> K0K0 = (1.08+/-0.28+/-0.11) x 10(-6) and the CP-violating charge asymmetry A(CP)(K0K+) = 0.10+/-0.26+/-0.03. Using a vertexing technique previously employed in several analyses of all-neutral final states containing kaons, we report the first measurement of time-dependent CP-violating asymmetries in B0 --> K(S)0K(S)0, obtaining S = -1.28(-0.73-0.16)(+0.80+0.11) and C = -0.40+/-0.41+/-0.06. We also report improved measurements of the branching fraction B(B+ --> K0 pi+) = (23.9+/-1.1+/-1.0) x 10(-6) and CP-violating charge asymmetry A(CP)(K0 pi+) = -0.029+/-0.039+/-0.010.