Studies of angular correlations in the decays Bs→J/ψφ by using the SIMUB generator

The performance of the method of angular moments on the ΔΓ_s determination from analysis of untagged decays is examined by using the SIMUB generator. The results of Monte Carlo studies with evaluation of measurement errors are presented. The method of angular moments gives stable results for the estimate of ΔΓ_s and is found to be an efficient and flexible tool for the quantitative investigation of the B⁰_s→J/ψφ decay. The statistical error of the ratio ΔΓ_s/Γ_s for values of this ratio in the interval [0.03,0.3] was found to be independent on this value, being 0.015 for 10⁵ events.     

Theoretical analysis of a remotely measurable soil evaporation transfer coefficient

Reducing soil evaporation (E) is an important way to increase water use efficiency for agriculture and sustainable water use. To achieve this goal, an accurate estimate of soil evaporation at the macro-scale level is necessary. By including the surface temperature of dry soil, the three temperatures model (3T model) was proposed as an estimate of E, and its temperature term was defined as the soil evaporation transfer coefficient (h_a). Although it has been primarily shown that h_a determines the boundaries of E, further studies of its properties are necessary because h_a has the application potential for remote sensing. The objectives of this study are to (1) investigate the relationships between h_a and those parameters that are important for E estimation but are not able to be remotely measured (aerodynamic resistance, soil surface resistance (r_s), and cumulative evaporation (E_c)); and (2) discuss the possibility for remote sensing application. Two experiments were carried out for these purposes: one in an open field and the other one in a closed growth chamber at constant temperature, humidity, and radiation. The following results were obtained: (1) Given the boundaries of 0 ≤ h_a ≤ 1, E was determined between its maximum value (potential evaporation rate) and minimum value (zero); (2) During the period when evaporation is controlled by r_s, a linear relation between h_a and log (r_s) is observed with a coefficient of determination r² = 0.76. Because h_a and r_s are independent variables with significant differences in properties and magnitudes, these results indicate that h_a and r_s are well related to each other; (3) During stage 1 of evaporation, cumulative evaporation (E_c) increased with time while h_a remained constant. Afterwards, h_a linearly increased with E_c. The relationships among h_a, E_c, r_a, and r_s would be useful for estimation of evapotranspiration by remote sensing.     

On s-uniform property of compressing sequences derived from primitive sequences modulo odd prime powers

Let Z/(p^e) be the integer residue ring modulo p^e with p an odd prime and e ≥ 2. We consider the suniform property of compressing sequences derived from primitive sequences over Z/(p^e). We give necessary and sufficient conditions for two compressing sequences to be s-uniform with α provided that the compressing map is of the form ?(x₀, x₁,...,x_e?1) = g(x_e?1) + η(x₀, x₁,..., x_e?2), where g(x_e?1) is a permutation polynomial over Z/(p) and η is an (e ? 1)-variable polynomial over Z/(p).     

A handy tool for history keeping of Geant4 tracks - J4HistoryKeeper

The Particle Flow Analysis (PFA) is currently under intense studies as the most promising way to achieve precision jet energy measurements required at the future linear e⁺e⁻ collider. In order to optimize detector configurations and to tune up the PFA it is crucial to identify factors that limit the PFA performance and clarify the fundamental limits on the jet energy resolution that remain even with the perfect PFA and an infinitely granular calorimeter. This necessitates a tool to connect each calorimeter hit in particle showers to its parent charged track, if any, and eventually all the way back to its corresponding primary particle, while identifying possible interactions and decays along the way. In order to realize this with a realistic memory space, we have developed a set of C++ classes that facilitates history keeping of particle tracks within the framework of Geant4. This software tool, hereafter called J4HistoryKeeper, comes in handy in particular when one needs to stop this history keeping for memory space economy at multiple geometrical boundaries beyond which a particle shower is expected to start. In this paper this software tool is described and applied to a generic detector model to demonstrate its functionality.     

fgh, a code for the calculation of Coulomb radial wave functions from series expansions

The code fgh is an up-dated version of a code coulfg (see [Seaton, Comput. Phys. Comm. 25 (1982) 87]), used for the calculation of the Coulomb functions f and g, analytic in the energy, for attractive potentials. The new code works for attractive and repulsive potentials and also gives the functions h which have simple asymptotic forms. There is an option to use either the variables (?,r) customary in atomic physics, or (for positive energies) (η,ρ) customary in nuclear physics. When (η,ρ) are used, the code also gives the functions F_?(η,ρ) and G_?(η,ρ).Use of series solutions can lead to loss of accuracy due to cancellation effects. fgh provides an indication of the number of significant figures lost due to cancellations.     

Development of a Geant4 solid for stereo mini-jet cells in a cylindrical drift chamber

Stereo mini-jet cells will be indispensable components of a future e⁺e⁻ linear collider central tracker such as JLC-CDC. There is, however, no official Geant4 solid available at present to describe such geometrical objects, which had been a major obstacle for us to develop a full Geant4-based simulator with stereo cells built in. We have thus extended Geant4 to include a new solid (TwistedTubs), which consists of three kinds of surfaces: two end planes, inner and outer hyperboloidal surfaces, and two so-called twisted surfaces that make slant and twisted φ-boundaries. Design philosophy and its realization in the Geant4 framework are described together with algorithmic details. We have implemented stereo cells with the new solid, and tested them using geantinos and Pythia events (e⁺e⁻→ZH at  GeV). The performance was found reasonable: the stereo cells consumed only 25% more CPU time than ordinary axial cells.     

Tension spline approach for the numerical solution of nonlinear Klein-Gordon equation

The nonlinear Klein-Gordon equation describes a variety of physical phenomena such as dislocations, ferroelectric and ferromagnetic domain walls, DNA dynamics, and Josephson junctions. We derive approximate expressions for the dispersion relation of the nonlinear Klein-Gordon equation in the case of strong nonlinearities using a method based on the tension spline function and finite difference approximations. The resulting spline difference schemes are analyzed for local truncation error, stability and convergence. It has been shown that by suitably choosing the parameters, we can obtain two schemes of O(k²+k²h²+h²) and O(k²+k²h²+h⁴). In the end, some numerical examples are provided to demonstrate the effectiveness of the proposed schemes.     

Collision dynamics of elliptically polarized solitons in Coupled Nonlinear Schrödinger Equations

We investigate numerically the collision dynamics of elliptically polarized solitons of the System of Coupled Nonlinear Schrödinger Equations (SCNLSE) for various different initial polarizations and phases. General initial elliptic polarizations (not sech$sech$-shape) include as particular cases the circular and linear polarizations. The elliptically polarized solitons are computed by a separate numerical algorithm. We find that, depending on the initial phases of the solitons, the polarizations of the system of solitons after the collision change, even for trivial cross-modulation. This sets the limits of practical validity of the celebrated Manakov solution. For general nontrivial cross-modulation, a jump in the polarization angles of the solitons takes place after the collision (‘polarization shock’). We study in detail the effect of the initial phases of the solitons and uncover different scenarios of the quasi-particle behavior of the solution. In majority of cases the solitons survive the interaction preserving approximately their phase speeds and the main effect is the change of polarization. However, in some intervals for the initial phase difference, the interaction is ostensibly inelastic: either one of the solitons virtually disappears, or additional solitons are born after the interaction. This outlines the role of the phase, which has not been extensively investigated in the literature until now.     

An implementation of granular dynamics for simulating frictional elastic particles based on the DL_POLY code

We have modified Daresbury Laboratory's replicated data strategy (RDS) parallel molecular dynamics (MD) package DL_POLY (version 2.13) to study the granular dynamics of frictional elastic particles. DL_POLY [Smith and Forester, The DL_POLY_2 User Manual v2.13, 2001; Forester and Smith, The DL_POLY_2 Reference Manual v2.13, 2001] is a MD package originally developed to study liquid state and macromolecular systems by accounting for various molecular interaction forces. The particles of interest in this study are macroscopic grains in pharmaceutical powders, with sizes ranging from tens to hundreds of microns. We have therefore substituted the molecular interaction forces with contact forces (including linear-dashpot, HKK interaction forces and Coulombic friction) while taking advantage of the RDS scheme. In effect, we have created a parallel Discrete Element Simulation (DES) code. In this paper, we describe the modifications made to the original DL_POLY code and the results from the validation tests of the granular dynamics simulations for systems of monodisperse spherical particles settling under gravity. The code can also be utilized to study particle packings generated via uniaxial compaction and, in some cases, simultaneous application of shear, at constant strain.     

Sputtered thin film piezoelectric aluminum nitride as a functional MEMS material

A comprehensive study on the complete process for the fabrication of AlN-based MEMS sensors and actuators is presented. Varying the bias voltage during the reactive rf sputtering enables to adjust the stress level in AlN films in the range of about 2?GPa. For the first time the influence of the rf bias power on the whole set of piezoelectric parameters was investigated. It could be shown that the dielectric permittivity, dielectric loss, rocking curve width, effective longitudinal piezoelectric coefficient d _33,f and effective transverse piezoelectric coefficient e _31,f remained unchanged. Further it was observed that piezoelectric AlN films could be deposited at low process temperatures of only 200?°C. Moreover an increase in the e _31,f coefficient with thicker films could be stated. Finally cone formation during wet etching was observed and revealed a formation of {01–12} planes which exhibit a slow etching rate. The c-textured growth of AlN starts directly at the Pt interface.     

A numerical differentiation library exploiting parallel architectures

We present a software library for numerically estimating first and second order partial derivatives of a function by finite differencing. Various truncation schemes are offered resulting in corresponding formulas that are accurate to order O(h), O(h²), and O(h⁴), h being the differencing step. The derivatives are calculated via forward, backward and central differences. Care has been taken that only feasible points are used in the case where bound constraints are imposed on the variables. The Hessian may be approximated either from function or from gradient values. There are three versions of the software: a sequential version, an OpenMP version for shared memory architectures and an MPI version for distributed systems (clusters). The parallel versions exploit the multiprocessing capability offered by computer clusters, as well as modern multi-core systems and due to the independent character of the derivative computation, the speedup scales almost linearly with the number of available processors/cores.

Program summary

Program title: NDL (Numerical Differentiation Library)Catalogue identifier: AEDG_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEDG_v1_0.htmlProgram obtainable from: CPC Program Library, Queen's University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 73 030No. of bytes in distributed program, including test data, etc.: 630 876Distribution format: tar.gzProgramming language: ANSI FORTRAN-77, ANSI C, MPI, OPENMPComputer: Distributed systems (clusters), shared memory systemsOperating system: Linux, SolarisHas the code been vectorised or parallelized?: YesRAM: The library uses O(N) internal storage, N being the dimension of the problemClassification: 4.9, 4.14, 6.5Nature of problem: The numerical estimation of derivatives at several accuracy levels is a common requirement in many computational tasks, such as optimization, solution of nonlinear systems, etc. The parallel implementation that exploits systems with multiple CPUs is very important for large scale and computationally expensive problems.Solution method: Finite differencing is used with carefully chosen step that minimizes the sum of the truncation and round-off errors. The parallel versions employ both OpenMP and MPI libraries.Restrictions: The library uses only double precision arithmetic.Unusual features: The software takes into account bound constraints, in the sense that only feasible points are used to evaluate the derivatives, and given the level of the desired accuracy, the proper formula is automatically employed.Running time: Running time depends on the function's complexity. The test run took 15 ms for the serial distribution, 0.6 s for the OpenMP and 4.2 s for the MPI parallel distribution on 2 processors.     

AFMM: A molecular mechanics force field vibrational parametrization program

AFMM (Automated Frequency Matching Method) is a program package for molecular mechanics force field parametrization. The method used fits the molecular mechanics potential function to both vibrational frequencies and eigenvector projections derived from quantum chemical calculations. The program optimizes an initial parameter set (either pre-existing or using chemically-reasonable estimation) by iteratively changing them until the optimal fit with the reference set is obtained. By implementing a Monte Carlo-like algorithm to vary the parameters, the tedious task of manual parametrization is replaced by an efficient automated procedure. The program is best suited for optimization of small rigid molecules in a well-defined energy minimum, for which the harmonic approximation to the energy surface is appropriate for describing the intra-molecular degrees of freedom.

Program summary

Title of program: AFMMCatalogue identifier: ADUZProgram summary URL:http://cpc.cs.qub.ac.uk/summaries/ADUZProgram obtainable from: CPC Program Library, Queen's University of Belfast, N. IrelandComputer: x86 PC, SGI, Sun MicrosystemsOperating system: GNU/Linux, BSD, IRIX, SolarisProgramming language used: PythonMemory required: 10 MbytesNo. of bits in a word: 32 or 64No. of processors used: 1Parallelized?: NoNo. of lines in distributed program, including test data, etc.:13 127No. of bytes in distributed program, including test data, etc.: 182 550Distribution format: tar.gzTypical running time: 24 hNature of the physical problem: Molecular mechanics force field parametrization.Method of solution:Fitting of the molecular mechanics potential to normal modes derived from quantum chemical calculations. The missing force field parameters are optimized via a merit function to obtain the optimal fit with the reference quantum mechanical set.     

Analysis of the efficiency of the Chor-Rivest cryptosystem implementation in a safe-parameter range

The Chor-Rivest cryptosystem, based on a high-density knapsack problem on a finite field F_q^h, was broken by Vaudenay for q≈200,h≈24, and h admitting a factor s verifying a certain condition. A new set of parameters q and h, which prevent this cryptosystem against Vaudenay’s attack, is presented and the computational aspects of its implementation in the Magma computational algebra system are analyzed.     

关于最优双环网的构造

在刘焕平等人工作的基础上,给出一个改进的h（h≥0）紧优双环网络的构造算法。利用VC++6.0编程来实现这一算法,对任意给定N,找出s（1<s<N）使得双环网络G（N;1,s）h（h≥0）紧优。首次给出了N在一亿之内,所有h（0≤h≤7）紧优双环网的个数及对应h的最小N值。并根据实验所得数据,指出Augilo和Fiol的求紧优双环网络算法的不足与错误。     

A scalable parallel algorithm for large-scale reactive force-field molecular dynamics simulations

A scalable parallel algorithm has been designed to perform multimillion-atom molecular dynamics (MD) simulations, in which first principles-based reactive force fields (ReaxFF) describe chemical reactions. Environment-dependent bond orders associated with atomic pairs and their derivatives are reused extensively with the aid of linked-list cells to minimize the computation associated with atomic n-tuple interactions (n?4 explicitly and ?6 due to chain-rule differentiation). These n-tuple computations are made modular, so that they can be reconfigured effectively with a multiple time-step integrator to further reduce the computation time. Atomic charges are updated dynamically with an electronegativity equalization method, by iteratively minimizing the electrostatic energy with the charge-neutrality constraint. The ReaxFF-MD simulation algorithm has been implemented on parallel computers based on a spatial decomposition scheme combined with distributed n-tuple data structures. The measured parallel efficiency of the parallel ReaxFF-MD algorithm is 0.998 on 131,072 IBM BlueGene/L processors for a 1.01 billion-atom RDX system.     

Stochastic optimization of ferroelectric ceramics for piezoelectric applications

An optimization model and numerical framework is developed to identify the optimal microstructure of ferroelectric (FE) materials. Piezoelectricity in polycrystalline ceramic FEs differs significantly from that of single crystals because of the presence of crystallites (grains) possessing crystallographic axes aligned imperfectly. The polarization and for that matter the piezoelectric properties of FEs are inextricably related to the orientation of individual crystallographic grains that constitute the polycrystal. The orientation of the grains fall in a Gaussian distribution after the poling process. The orientation distribution parameters, (viz., the standard deviation σ and mean μ) hence, would play the crucial role in the effective piezoelectric properties of FE polycrystals. We have applied a stochastic optimization combined with homogenization to determine the optimal distribution parameters which dictates the orientation distribution (texture) of an ideal ferroelectric polycrystal. This procedure would be used to find out the optimum piezoelectric properties characterised by the piezoelectric coefficients e_ijke_{\it ijk}. The method is applied with an objective to maximize the piezoelectricity of ferroelectric BaTiO₃ which in turn maximizes the electromechanical coupling. Convergence studies are made in order to arrive at a meaningful representative volume element for the computation. Focussing on the polar component of piezoelectric coefficient, e ₃₃, the optimization course is perfected. Apparent enhancement of piezoelectric coefficient e_ijke_{\it ijk} is observed in an optimally oriented BaTiO₃ single crystal. In polycrystalline ceramics, optimal grain configurations that shows better piezoelectric performance than polar ferroelectrics are derived. Our optimization model provides designs for materials with better piezoelectric performance, which would stimulate further studies involving materials possessing higher spontaneous polarization.     

Fittino, a program for determining MSSM parameters from collider observables using an iterative method

Provided that Supersymmetry (SUSY) is realized, the Large Hadron Collider (LHC) and the future International Linear Collider (ILC) may provide a wealth of precise data from SUSY processes. An important task will be to extract the Lagrangian parameters. On this basis the goal is to uncover the underlying symmetry breaking mechanism from the measured observables. In order to determine the SUSY parameters, the program Fittino has been developed. It uses an iterative fitting technique and a Simulated Annealing algorithm to determine the SUSY parameters directly from the observables without any a priori knowledge of the parameters, using all available loop-corrections to masses and couplings. Simulated Annealing is implemented as a stable and efficient method for finding the optimal parameter values. The theoretical predictions can be provided from any program with SUSY Les Houches Accord interface. As fit result, a set of parameters including the full error matrix and two-dimensional uncertainty contours are obtained. Pull distributions can automatically be created and allow an independent cross-check of the fit results and possible systematic shifts in the parameter determination. A determination of the importance of the individual observables for the measurement of each parameter can be performed after the fit. A flexible user interface is implemented, allowing a wide range of different types of observables and a wide range of parameters to be used.

Program summary

Program title: FittinoCatalogue identifier: ADWNProgram summary URL:http://cpc.cs.qub.ac.uk/summaries/ADWNLicensing provisions: GNU General Public LicenseProgramming language:C++Computer: any computerOperating system: Linux and other Unix flavorsRAM: ca. 22 MBNo. of lines in distributed program, including test data, etc.: 111 962No. of bytes in distributed program, including test data, etc.: 1 006 727Distribution format: tar.gzNumber of processors used: 1External routines: The ROOT data analysis framework, the SPheno spectrum calculator (included in the distribution). (SPheno may be replaced by any SUSY code which makes predictions for observables and communicates via the SLHA.)Nature of problem: Provided supersymmetry is realized in Nature, a wealth of data will become available at the Large Hadron Collider (LHC) and the International Linear Collider (ILC). One of the most important tasks will be to extract the SUSY Lagrangian parameters from the measured observables. The large number of SUSY parameters and complicated correlations induced by loop corrections make the parameter determination difficult. Starting a global SUSY parameter fit initialized with tree-level estimates turned out to be an insufficient approach because the MINUIT fitting algorithm is likely to get stuck in local minima.Solution method: To overcome the encountered problems without using a priori knowledge, two strategies have been implemented in Fittino. The first one performs the fit in several steps (sub-sector fit method). It starts fitting certain sub-sets of parameters to certain sub-sets of observables and thereby slowly improves the parameter values. Finally the values are good enough to start a global SUSY parameter fit.The second approach uses simulated annealing to improve the tree-level estimates of the parameters to an extend where MINUIT succeeds to perform a global SUSY parameter fit.Restrictions: The current version of Fittino (version 1.1.1) assumes that there is no CP violation in the SUSY sector, no mixing between generations and no mixing within the first two generations.Running time: Depending on the complexity of the problem, the running time varies from a few minutes to several weeks.     

On stabilization of energy for Hamiltonian systems

We study post-stabilization of numerical integrators for an autonomous Hamiltonian system in the form H=H₁+H₂, where H₁ and H₂ are two constants of motion. It is better to stabilize the two energies H₁ and H₂, respectively. As a particular case, the effectiveness of post-stabilization by the total energy is equivalent to one by the two independent energies when the splitting Hamiltonian becomes isotropic.     

Large scale fractal aggregates using the tunable dimension cluster-cluster aggregation

The tunable dimension cluster-cluster aggregation (tdCCA) [R. Thouy, R. Jullien, J. Phys. A: Math. Gen. 27 (1994) 2953] provides a computational model for creating fractal aggregates with a tunable fractal dimension. A straightforward implementation of this model requires a computational effort scaling with O(N_total⁴) of the number of particles N_total. By applying two minor changes to the algorithm the computational effort can be reduced to O(N_total²) and allows an efficient parallel implementation of the tdCCA. On a modern parallel computer a fractal aggregate of one million particles has been built in less than 24 h.     

An integrated tool for loop calculations: aITALC

aITALC, a new tool for automating loop calculations in high energy physics, is described. The package creates Fortran code for two-fermion scattering processes automatically, starting from the generation and analysis of the Feynman graphs. We describe the modules of the tool, the intercommunication between them and illustrate its use with three examples.

Program summary

Title of the program:aITALC version 1.2.1 (9 August 2005)Catalogue identifier:ADWOProgram summary URL:http://cpc.cs.qub.ac.uk/summaries/ADWOProgram obtainable from:CPC Program Library, Queen's University of Belfast, N. IrelandComputer:PC i386Operating system:GNU/Linux, tested on different distributions SuSE 8.2 to 9.3, Red Hat 7.2, Debian 3.0, Ubuntu 5.04. Also on SolarisProgramming language used:GNU Make, Diana, Form, Fortran77Additional programs/libraries used:Diana 2.35 (Qgraf 2.0), Form 3.1, LoopTools 2.1 (FF)Memory required to execute with typical data:Up to about 10 MBNo. of processors used:1No. of lines in distributed program, including test data, etc.:40 926No. of bytes in distributed program, including test data, etc.:371 424Distribution format:tar gzip fileHigh-speed storage required:from 1.5 to 30 MB, depending on modules present and unfolding of examplesNature of the physical problem:Calculation of differential cross sections for e⁺e⁻ annihilation in one-loop approximation.Method of solution:Generation and perturbative analysis of Feynman diagrams with later evaluation of matrix elements and form factors.Restriction of the complexity of the problem:The limit of application is, for the moment, the 2→2 particle reactions in the electro-weak standard model.Typical running time:Few minutes, being highly depending on the complexity of the process and the Fortran compiler.