PC Farms for Triggering and Online Reconstruction at HERA—B

The HERA-B data acquisition and triggering systems make use of Linux PC farms for triggering and online event reconstruction.We present in this paper the requirements,implementation and performance of both PC farms.They have been fully working during the year 2000 detector and trigger commissioning run.     

CATS：a Cellular Automation for Tracking in Silicon for the HERA—B Vertex Detector

A track reconstruction program CATS based on a cellular automaton has been developed for the vertex detector system of the HERA-B experiment at DESY,A segment model of the cellular automation used for tracking can be regarded as local discrete form of the Denby-Peterson neural net.Since 1999 CATS has been used to reconstruct data collected in HERA-B.Results on the tracking performance,and accuracy of estimates and computing time are presented.     

Studies for Optimization of Data Analysis Queries for HEP Using HERA—B Commissioning Data

In this paper we present an overview of the ongoing studies to build up a framework that supports the analysis after the reprocessing phase.This framework aims to develop a standard data query language for the HEP community,The related studies have been considering the relational database model as possible approach opposed to the object model.Several optimizing and tunning techniques are being used in technologies like DB2[3],Oracle[5] and Root[2],that are simultaneously being evaluated.The experience obtained can be seen as a valuable testbed for the future LHC and simultaneously as interesting input for the development of the GRID.     

Centrality Dependence of Flow in High—Energy Nucleus—Nucleus Collisions

Directed flow and elliptic flow of final state particles in high-energy nucleus-nucleus collisions in the EMU01 experiment have been studied.The dependences of directed flow and elliptic flow on incident energy and impact centrality of outgoing particles are presented.The results exhibit strong dependence of flow on centrality and energy.We also suggest a more reliable way to determine the event plane resolution here.     

Experimental Test of the Non—reproducibility of Cross Sections in Dissipative Reactions

Two independent measurements of cross sections for the ^19F ^93Nb dissipative heavy ion collisions have been performed at incident energies from 100 to 108MeV in steps of 250keV.In the two measurements,two independently prepared targets were used.All other experimental conditions were identical in both experiments.The data indicate that non-reproducibility of the non-self-averaging oscillation is yielded in the two measurements.This supports the recent theoretical predictions of spontaneous coherence,slow phase randomization and extreme sensitivity in highly excited complex quantum systems.     

Rare Decay B→Xsvv in the Two—Higgs—Doublet Model of Type—Ⅲ

In this paper, we calculated the new physics contribution to theoretically very clean rare decay B→X_sνν in the general two-Higgs-doublet model (model III). Within the considered parameter space, we found that (a) the new physics contribution can provide one to two orders of enhancement to the branching ratio B(B→X_sνν) and can saturate the experimental bound on B(B→X_sνν) in some regions of the parameter space; (b) besides the CLEO data of B→X_sγ, the ALEPH upper limit on B(B→X_sνν) also leads to further constraint on the size of the Yukawa coupling λ_tt: λ_tt< 6.4 for λ_bb=2.7 and m_H⁺=200 GeV.     

运用MUJ—ⅡB电脑计时器研究滑块的运动学问题

运用MUJ－ⅡB电脑计时器研究处于气垫导轨上滑块的运动情况,记录下各段预定位移的时间间隔及各点的瞬时速度,直观表现了滑块作匀加速运动的轨迹及特点,验证了滑块运动的速度公式,位移公式等。     

Effect of Metallic Film in Diamond Growth from an Fe—Ni—C System at High Temperature and High Pressure

The metallic film surrounding a diamond single crystal,which plays an important role the diamond growth from and Fe-Ni-C system,has been successfully investigated by using transmission-electron microscopy(TEM),Raman layer(near diamond)of the film by TEM and Raman spectroscopy,but a parallel relationship exists between the(111) plane of γ-(Fe,Ni) and the (100) plane of (Fe2Ni)3C in this region.Compared with that of the film has an increase of 0.9V.According to the microstructures on the film obtained by the TEM.Raman spectra,and XPS,the catalytic mechanism of the film may be assumed as follows.In the surface layer of the film,iron and nickel atoms in the γ-(Fe,Ni) lattice can absorb carbon atoms in the (Fe,Ni)3C lattice and make them transform to an sp^3-like state.Then carbon atoms with the sp^3-like structure are separated from the (Fe,Ni)3C and stack on the growing diamond crystal.This study provides a direct evidence for the diamond growth from a metallic catlayst-graphite system under high temperature and high pressure.     

Entropy in the NUT—Kerr—Newman Black Holes in the Background of de Sitter Spacetime

We calculate the entropy of the fermion field in the NUT-Kerr-Newman black holes in the background of the de Sitter spacetime by using the improved brick-wall method and the membrane model.Here the Euler characteristic of the black holes is over two.The results show that,as the cut-off is properly chosen,the entropy in the black hole satisfies the Bekenstein-Hawking area law.     

Coupled—Channel Investigation of the Collision of Protons and Antiprotons with hydrogen—Like Atoms in the 2s States

The influence of the electric charge of both the projectile and the target nucleus on the cross section of the inelastic collision of protons and antiprotons with atoms is investigated at energies ranging from 1 to 2500Kev,The impact parameter method is used to analyse the cross sections of the excitation of the n=3 states of H atom and He^ ,Li^2 ions being initially in the excited 2s states.The calculated cross sections for hydrogen atome are compared with the other theoretical results based on coupled-channels methods.     

Calculations of Electron Structure of Endohedrally Confined Helium Atom with B—Spline Type Functions

The B-spline basis set method is used to study the properties of helium confined endohedrally at the geometrical centre of a fullerene.The boundary conditions of the wavefunctions can be simply satisfied with this method.From our results,the phenomenon of “mirror collapse” is found in the case of confining belium.The interesting behaviors of confining helium are also discussed.     

Spectral Properties of Endohedrally Confined Hydrogen Atom and Hydrogen—Like Ions Obtained by Using B—Spline Basis Set

A B-spline method has been used to calculate the electron structure of endohedrally confined hydrogenlike atoms.The boundary conditions were conveniently satisfied with such the method.The evolution of the energy spectrum,as function of the depth of the confining well,exhibits a “mirror collapse”.Ions with higher ionicity have more “collapse lines”,the energies change more sharply at “collapse points”,and the oscillator strengths change more violently with the depth of the confining well.     

Impacts of the Soft—Gluon Exchanges on B→ππ Decays

We have investigated the role of soft-gluon exchanges in B→ππ,using the light-cone sum rules in quantum chromodynamics,The calculations are carried out not only for the tree operators but also for the penguin operators.We conclude that soft-gluon exchanges contribute to the decay amplitudes,noticeably on some decay channels,and thus cannot be neglected.     

Calculation of Kaon Electromagnetic Form Factor in the Framework of Coupled Schwinger—Dyson and Bethe—Salpeter Formulation

The kaon electromagnetic form factor is calculated in the framework of coupled Schwinger-Dyson equation in rainbow approximation and Bethe-Salpeter equation in ladder approximation with the modified flat-bottom potential,which is the combination of the flat-bottom potential with considerations for the infrared and ultraviolet asymptotic behaviours of the effective quark-gluon coupling.All our numerical results give good fit to experimental values and other theoretical results.     

Characterization of Mn—Doped Ba1—xSrxTiO3 Thin Films Prepared by the Sol—Gel Method

Undoped and Mn-doped Ba1-xSrxTiO3(BST) thin films have been fabricated on Pt/Ti/SiO2/Si by an aqueous acetate sol-gel method.The BST stock solution can be easily mixed with an aqueous metal ion solution and is stable at room temperature.The annealing temperature of the doped and undoped films is between 650-750℃.The x-ray photoelectron spectra results show that the Mn2p3/2 valence state in the BST is the sampe as that of the original Mn(Ⅱ） dopant,The dielectric constant of the BST thin films can be increased to 800,and the loss tangent can be decreased to 0.01 due to the Mn(Ⅱ） doping.The leakage current of the BST films can also be greatly reduced.     

Tight—binding calculation of the electronic states of bulk—terminated GaAs（311）A and B surfaces

We have carried out theoretical investigations on the electronic structure of GaAs(311)A and GaAs(311)B surfaces. The bulk electronic structure of GaAs has been described by the second-neighbour tight-binding formalism and the surface electronic structure was evaluated via an analytic Green function method. First, we present the surface band structure together with the projected bulk band of both Ga-terminated and As-terminated for GaAs(311)A and GaAs(311)B surfaces, respectively. In each case, the number of surface states is determined, and the localized surface features and orbital properties of these surface states along Γ-Y-S-X-Γ high symmetry lines of the surface Brillouin zone are discussed. For the Ga-terminated GaAs(311)A (1×1) surface, we have tested two possible structure models, i.e. "the bridge site" and "the hollow site" models. In comparison with the angle-resolved photoelectron spectroscopy studied recently, the results have shown that the surface electronic states of the hollow site model are in good agreement with the experiments, whereas those of the bridge site model are not. So we have concluded that the hollow site model is favourable for the Ga-terminated GaAs(311) (1×1) surface and the bridge site model should be excluded.     

Numerical Investigation for the Properties of Nonintegrable Quantum SYstems Eigenspace in the Line of Quantum—Classical Correspondence

The properties of the eigenspace of nonintegrable quantum systems are explored in detail in the light of the viewpoint of quantum-classical completely correspondence proposed recently by Xu et al.The changes of the topological structure in the state space of autonomous quantum system due to the nonlinear resonance are displayed numerically with the uncertainty measure of a special initial state ρα（λ） and the transformation matrix U(λ δλ-λ-δλ）,The statistical behavior of the subspace occupied by the state in eigenspace of quantum nonintegrable system is discussed carefully with the help of a special renormalization method.The results show that the randomness of effective Hamilonian matrix,the transition matrix and the nearest level spacings in this region can be described by random matrix theory.And the extent of agreement of our calculation with the prediction of GOE is in correspondence to the extent of the classical torus violation.     

Dependence of in—tube doping on the radius and helicity of single—wall carbon nanotubes

Using the Lennard－Jones interaction potential between the impurity atom and carbon atom, we have studied the dependence of in-tube impurity doping on the radius of a single-wall carbon nanotube (SWNT), as well as its helicity. The obtained results show that the radius of the most stably doped SWNT is different for different kinds of impurity atoms. This is useful for producing the required doped SWNT. In addition, it is found that the helicity of tube has a strong effect on the potential energy of the atoms doped in the SWNT.     

High pressure effects on the luminescent properties and crystal structure of magnesium 8—hydroxyquinoline complex

The fluorescence emission and X-ray diffraction of magenesium 8-hydroxyquinoline complex(Mgq2) have been measured at high pressure up to 14 GPa.It has been found that pressure can influence the emission dramatically.At relative lower pressure(less than 2.5GPa) the fluorescence of Mgq2 changes slightly,but the emission drops quickly with increase of the pressure when the pressure gets higher than 2.5GPa.The results of in situ energy dispersive X-ray diffraction at high pressure with synchrotron radiation indicate that there is a phase transition at about 2.5-3GPa for Mgq2 crystal.2001 Elsevier Science B.V.All rights reserved.     

Influence of Doping on the Mott Metal—Insulator Transition in Infinite Dimensions

We have studied the effect of hole-doping on the established scenerio of the first-order Mott metal-insulator transition (MIT) at half-filling using dynamical mean-field theory and exact diagonalization technique.The mott insulator state is changed into metallic state immediately as holes are doped into the system.The latter is expected to be Fermi liquid.The previously found unanalytical structure of MIT no longer exists for doping as small as 2 percent.We compare our results with that obtained from Gutzwiller approximation.