Simulation System of Internal-target Detector at HIRFL-CSRm

HIRFL-CSRm will accelerate the proton beam up to 2.8 GeV. The interesting physics, such as the hadron spectrum, di-baryon state and the rare decay mode of the neutral mesons can be investigated with such beams. The corresponding detector as introduced in Ref.[1] is an internal-target 4π detector which is composed of the forward detector (including position detector and hadron calorimeter) to detect particles emitted at forward angles, and the center detector (including tracker, plastic scintillator barrel and EM calorimeter) to measure momentum and energy loss of the charged particle, and the energy and emission angle of the high energy photon at central and backward angles. To design such a complex detector, the Monte-Carlo (MC) simulation is definitely necessary.     

Pd-Si Binary Bulk Metallic Glass Prepared at Low Cooling Rate

We report that binary bulk metallic glasses can be made up to 6ram in diameter in a Pd Si ahoy system by air cooling at slow cooling rate (about 8 K/s). The high stability of the undercooled liquid and the large glass-forming ability (GFA) of the binary alloy are contributed to the removing of heterogeneous impurities in the alloy melt by employing the fluxing technique. It has been found that decreasing cooling rate can increase the supercooled liquid region and thermal stability of the glassy alloy. After fluxing, a wider supercooled liquid region (△T = 58 K) and higher glass-forming ability have been obtained in a Pd81Si19 binary glassy alloy prepared by slow cooling rate.     

Stochastic perturbation in quasi—ideal dispersion—managed soliton system

The model of stochastic perturbation is built up systematically in quasi-ideal dispersion-managed soliton system,its influence on soliton propagation is investigated by both the variational approach and the numerical simulation,and it is found that the stochastic perturbation leads to disintegration of soliton and enhances the interaction between solitons.The nonlinear gain and filter are introduced to suppress effectively the influence on both soliton propagation and interaction.     

Transverse Momentum and Rapidity Distributions of Φ Mesons Produced in Pb-Pb Collisions at SPS Energies

To investigate the excitation degree of the interacting system and the penetrating power of the projectile nucleus and to understand their dependences on incident energy, the transverse momentum and rapidity distributions of particles produced in nucleus-nucleus collisions at high energies are studied by using a multisource ideal gas model. The calculated results are compared with the most recent NA49 experimental data of φ mesons produced in Pb-Pb collisions at the Super Proton Synchrotron （SPS） energies.     

Energy—Momentum Pseudo—tensor of Cylindrical Gravitational Waves of Both the Polarized States

According to the Einstein-Tolman expression of the energy-momentum pseudo-tensor(EMPT),we calculate the EMPT of cylindrical gravitational waves (CGW) of both the polarized states (BPS) in cylindrical polar coordinates and Cartesian coordinates.We find that Cartesian coordinates are the more suitable coordinates to describe the CGW of BPS.     

Stochastic flows,reaction — Diffusion processes,and morphogenesis

Recently, anexact procedure has been introduced [C. A. Walsh and J. J. Kozak,Phys. Rev. Lett. 47:1500 (1981)] for calculating the expected walk length 〈n〉 for a walker undergoing random displacements on a finite or infinite (periodic)d-dimensional lattice with traps (reactive sites). The method (which is based on a classification of the symmetry of the sites surrounding the central deep trap and a coding of the fate of the random walker as it encounters a site of given symmetry) is applied here to several problems in lattice statistics for each of whichexact results are presented. First, we assess the importance of lattice geometry in influencing the efficiency of reaction-diffusion processes in simple and multiple trap systems by reporting values of 〈n〉 for square (cubic) versus hexagonal lattices ind=2, 3. We then show how the method may be applied to variable-step (distance-dependent) walks for a single walker on a given lattice and also demonstrate the calculation of the expected walk length 〈n〉 for the case of multiple walkers. Finally, we make contact with recent discussions of “mixing” by showing that the degree of chaos associated with flows in certain lattice systems can be calibrated by monitoring the lattice walks induced by the Poincaré map of a certain parabolic function.     

Angular Momentum—Radius Entanglement for an Electron in a Uniform Magnetic Field

Noticing that the angular monentum operator Lz commutes with the square of radius operator,R^2,of the orbit track of an electron in a uniform magnetic field,we reveal that a new entanglement is inherent to the common eigenvector of the operators Lz and R^2.     

Boson—Fermion Correspondence on the Circle via Quantum Stochastic Calculus

The quantum stochastic differential formula dB = (–1)dA, known to relateboson and fermion fields A and B, respectively, on the Fock space over L ²(R₊),is shown to hold in a modified form in a Fock space associated with the nontrivialcomplex line bundle over the circle S ¹.     

Stochastic Multiresonance for Periodically Modulated Noise in a Single—Mode Laser

Multiplicatively introducing the noise and the signM into the gain-noise model of a single-mode laser system, we detect the two forms of stochastic resonance (the single-peak form stochastic resonance and stochastic multiresonance) in the curve of the dependence of signal-to-noise ratio upon the noise correlation time. Moreover, when the correlation coefficient and the intensities of both noises are changed, the two forms of stochastic resonance alternate.     

The Stochastic Approach in Analysis—the Structures with Vacancies and Impurities

The stochastic approach to the problem of deformed bulk structures is a unique possibility for obtaining a so–so real picture of physical processes in these structures. The chain of identical atoms with random distances between neighbours as well as the chain with random masses at equal distances is analysed. These analyses were generalized to complex chains, which are spatially and mass deformed. The approximations used were incommensurability; one and more rough, continual approximation. The probabilities are of exponential type. It means that the error in estimation on the basis of stochastical method can go to 100% maximally.     

Entanglement of the Common Eigenvector of Two Particles‘ Center—of—Mass Coordinate and Mass—Weighted Relative Momentum

We reveal that the common eigenvector of two particles‘ center-of-mass coordinate and mass-weighted relative momentum is an entangled state.Its Schmidt decomposition exhibits that the entanglement involves squeezing which depends on the ration of two particles‘ masses.The corresponding entangling operators are derived.     

Search for Scalar Resonance in the ωϕ System in the Pion-Nuclear Interaction at Momentum of 29 GeV/c

Physics of Atomic Nuclei - The charge-exchange reaction $${{\pi }^{ - }}p \to n\omega (783)\phi (1020)$$ , $$\omega \to {{\pi }^{ + }}{{\pi }^{ - }}{{\pi }^{0}}$$ , $$\phi \to {{K}^{ + }}{{K}^{ -...     

Stochastic resonance in parabolic—bistable potential system with an additive colour noise

We propose a new model (parabolic bistable system) with a colour noise source. In the presence of periodic input signal, we investigate the output signal to-noise ratio and the power spectral density of output signal, in which the self-correlation time may be an arbitrary value with no restriction. We find that the curves of signal-to-noise ratio versus the noise intensity D exhibits a bell-shape behaviour. The peak height increases with the increasing value of amplitude A_0 of the input signal. However, the position of peak does not shift. Moreover, the signal-to-noise ratio is insensitive to the modulation frequency Ω, which completely differs from result of Ref.[6]. The power spectral density also has similar behaviour.     

Momentum spectra of identified hadrons at e+e? annihilations: comparison with QCD calculations

Charged particle momentum distributions are studied in the reaction e⁺e⁻ → hadrons, using data collected with the AMY detector at center of mass energy of 58 GeV. The measured distributions and derived quantities in combination with the corresponding results obtained at both lower and higher center of mass energies are compared to QCD predictions in theoretical approach to study the energy dependence of the strong interaction, and to test QCD as the theory describing it. To achieve this, the mean charged particle multiplicity, the charged particle momentum spectrum and its peak position are compared with predictions of the modified-leading logarithmic approximation. In general, good agreement is observed between the data and the above approximation in the regions where the model is expected to be valid. In addition the strong coupling constant α _s is determined from a fit of the QCD prediction to x _p distribution of the Feynman scaling. When we leave α _s as a free parameter in the fit we obtain α _s = 0.115 ± 0.008.     

Energy and Angular Momentum ofthe Weak Gravitational Waves on the Schwarzschild Background — Quasilocal Gauge-invariant Formulation

A four-dimensional spherically covariantgauge-invariant quasilocal framework for theperturbation of the Schwarzschild metric is given. Animportant ingredient of the analysis is the concept ofquasilocality, which does duty for the separation ofangular variables in the usual approach. A precise andfull analysis for the mono-dipole part ofthe theory is presented. Direct construction (from theconstraints) of the reduced canonical structure for theinitial data and explicit formulae for thegaugeinvariants are proposed. The reduced symplecticstructure explains the origin of the axial and polarinvariants. This enables one to introduce an energy andangular momentum for the gravitational waves, which isinvariant with respect to the gauge transformations. Anexplicit expression for the energy and new proposition for angular momentum is introduced, inparticular, compatibility of theChristodoulou-Klainerman S.A.F. condition withwell-possedness of our functionals is checked. Bothgenerators (energy and angular momentum) represent quadratic approximation ofthe adm nonlinear formulae in terms of the perturbationsof the Schwarzschild metric. The previously knownresults are presented in a new geometric andself-consistent way. Both degrees of freedom fulfill thegeneralized scalar wave equation. For the axial degreeof freedom the radial part of the equation correspondsto the Regge-Wheeler result and for the polar one we get the Zerilli result.     

QCD at finite temperature—a variational approach

We develop here a nonperturbative framework to study quantum chromodynamics (QCD) at finite temperatures using the thermofield dynamics (TFD) method of Umezawa. The methodology considered here is selfconsistent and variational. There is a dynamical generation of a magnetic gluon mass. This eliminates the infrared problems associated with perturbative QCD calculations at finite temperatures. We obtain here the thermodynamical quantities like free energy density, pressure and entropy density. We also calculate the temperature dependence of SVZ parameter . The condensate vanishes at the critical temperature in accordance with recent hot sum rule calculations. The present method gives an insight to the vacuum structure in QCD at zero temperature as well as at finite temperatures in a coordinated manner.     

Kapitza resistance at the liquid—solid interface

Using equilibrium and non-equilibrium molecular dynamics simulations, we determine the Kapitza resistance (or thermal contact resistance) at a model liquid-solid interface. The Kapitza resistance (or the associated Kapitza length) can reach appreciable values when the liquid does not wet the solid. The analogy with the hydrodynamic slip length is discussed.