17427337
SUSY23 V2.0 : an event generator for supersymmetric processes at e+e- colliders
Abstract S usy23 is a Monte Carlo package for generating supersymmetric (SUSY) processes at e + e − colliders. Twenty-three types of SUSY processes with 2 or 3 final state particles at tree level are included in version 2.0. S usy23 addresses event simulation requirements at e + e − colliders such as LEP. Matrix elements are generated by GRACE with the helicity amplitude method for processes involving massive fermions. The phase space integration of the matrix element gives the total and differential cross sections, then unweighted events are generated. Sparticle widths and decay branching ratios are calculated. Each final state particle may then decay according to these probabilities. Spin correlations are taken into account in the decays of sparticles. Corrections of initial state radiation (ISR) are implemented in two ways, one is based on the electron structure function formalism and the second uses the parton shower algorithm called QEDPS. Parton shower and hadronization of the final quarks are performed through an interface to JETSET.
117876117
Present Status of GRACE/SUSY-loop
GRACE/SUSY-loop is a program package for the automatic calculation of the MSSM amplitudes in one-loop order. We present features of GRACE/SUSY-loop, processes calculated using GRACE/SUSY-loop and an extension of the non-linear gauge formalism applied to GRACE/SUSY-loop.
7717301
Automatic one loop calculation of MSSM processes with GRACE
Abstract We have developed the system for the automatic computation of cross-sections, GRACE/SUSY , including the one-loop calculations for processes of the minimal supersymmetric extension of the standard model. For an application, we investigate the process e + e - → Z 0 h 0 .
14998834
Automatic Computation of Cross Sections in HEP ∗ Status of GRACE System
For the study of reactions in High Energy Physics (HEP) automatic computation systems have been developed and are widely used nowadays. GRACE is one of such systems and it has achieved much success in analyzing experimental data. Since we deal with the cross section whose value can be given by calculating hundreds of Feynman diagrams, we manage the large scale calculation, so that effective symbolic manipulation, the treat of singularity in the numerical integration are required. The talk will describe the software design of GRACE system and computational techniques in the GRACE. High energy experimental physics has produced excellent results thanks to the progress of the detectors and the development of the high energy accelerators with high luminosity. Accordingly, the accurate theoretical computation is required to compare experimental results with theoretical predictions. On the other hand, as the beam energy becomes higher, there appear the physics processes with many final state particles. As a matter of course the number of relevant Feynman diagrams becomes huge. This means that Feynman amplitude calculation is practically impossible when one calculates cross sections by hands. Since the perturbative calculation in quantum field theory is well-defined, it can be realized as an automatic computation system. There appeared several systems, for instance, CompHEP 1) and FeynArt/FeynCalc 2) , in HEP and nowadays the automatic computation of Feynman amplitudes becomes common. We have developed an automatic computation system named GRACE. 3) In section 2, we describe the feature of GRACE system as a concrete example of such system. In section 3, several physical achievements by GRACE are briefly explained. In section 4, we discuss the techniques in GRACE from the view point of computing.
5722422
The automatic computation for SUSY processes
AbstractWe have constructed a system for the automatic computation of cross-sectionsfor the processesof the SUSY QED by the extension of the GRACE system includinga Majorana fermion. The system has also been applied to another model includingMajorana fermions, MSSM, by the deﬁnition of the model ﬁle. IntroductionIthas been widely believed that there exists a symmetry called supersymmetry (SUSY)between bosons and fermions at the uniﬁcation-energy scale. It, however, is a brokensymmetry at the electroweak-energy scale. The relic of SUSY is expected to remain asa rich spectrum of SUSY particles, partners of usual matter fermions, gauge bosons andHiggs scalars, named sfermions, gauginos and higgsinos, respectively [1, 2, 3].The neutral gauginos and higgsinos are Majorana fermions, which become the mixedstates called neutralinos. Since anti-particles of Majorana fermions are themselves, thereexists so-called ‘Majorana-ﬂip’, the transition between particle and anti-particle. This hasbeen the most important problem which we should solve when we realize the automaticsystem for computation of the SUSY processes.1
119094900
A System for the Automatic Computation of Cross-Sections Including SUSY Particles
We introduce a new method to treat Majorana fermions on the GRACE system, which has already been developed for the computation of the matrix elements for the processes of the standard model. In the standard model, we already have included such particles as Dirac fermions, gauge bosons and scalar bosons in the system. On the other hand, there are four Majorana fermions called neutralinos in the minimal SUSY standard model (MSSM). In consequence, we have constructed a system for the automatic computation of cross-sections for the processes of the MSSM. It is remarkable that our system is also applicable for another model including Majorana fermions once the definition of the model file is given.
122391514
Density matrix of an impenetrable Bose gas and the fifth Painlevé transcendent
Abstract The quantal system of Bose particles described by the non-linear Schrodinger equation i∂φ/∂t = - 1 2 ∂2φ/∂x2 + cφ∗φ2, with c= cxf∞ and via the ground state with finite particle density, is the 1- dimensional gas of impenetrable bosons studied by M. Girardeau, T.D. Schultz, A. Lenard, H.G. Vaidya and C.A. Tracy. We show that the 2-point (resp. 2n-point) function, or the 1-particle (resp. n-particle) reduced density matrix, of this system satisfies a non-linear differential equation (resp. a system of non-linear partial differential equations) of Painleve type. Derivation of these equations is based on the link between field operators in a Clifford group and monodromy preserving deformation theory, which was previously established and applied to the 2-dimensional Ising model and other problems. Several related topics are also discussed.
119144130
Creation operators for the Fateev-Zamolodchikov spin chain
In previous works, we studied the problem of constructing a basis in the space of local operators for an anisotropic XXZ spin chain with spin 1/2 such that the vacuum expectation values have a simple form. For this, we introduced fermionic creation operators. Here, we extend this construction to the spin-1 case. Using a certain version of the fusion procedure, we find two doublets of fermionic creation operators and one triplet of bosonic creation operators. We prove that the basis obtained by the action of these operators satisfies the dual reduced quantum Knizhnik-Zamolodchikov equation.
119733514
Fermionic structure in the sine-Gordon model: Form factors and null-vectors
Abstract The form factor bootstrap in integrable quantum field theory allows one to capture local fields in terms of infinite sequences of Laurent polynomials called ‘towers’. For the sine-Gordon model, towers are systematically described by fermions introduced some time ago by Babelon, Bernard and Smirnov. Recently the authors developed a new method for evaluating one-point functions of descendant fields, using yet another fermions which act on the space of local fields. The goal of this paper is to establish that these two fermions are one and the same object. This opens up a way for answering the longstanding question about how to identify precisely towers and local fields.
119214853
Hidden Grassmann Structure in the XXZ Model II: Creation Operators
In this article we unveil a new structure in the space of operators of the XXZ chain. For each α we consider the space $${\mathcal W_\alpha}$$ of all quasi-local operators, which are products of the disorder field $${q^{\alpha \sum_{j=-\infty}^0\sigma ^3_j}}$$ with arbitrary local operators. In analogy with CFT the disorder operator itself is considered as primary field. In our previous paper, we have introduced the annhilation operators b(ζ), c(ζ) which mutually anti-commute and kill the “primary field”. Here we construct the creation counterpart b*(ζ), c*(ζ) and prove the canonical anti-commutation relations with the annihilation operators. We conjecture that the creation operators mutually anti-commute, thereby upgrading the Grassmann structure to the fermionic structure. The bosonic operator t*(ζ) is the generating function of the adjoint action by local integrals of motion, and commutes entirely with the fermionic creation and annihilation operators. Operators b*(ζ), c*(ζ), t*(ζ) create quasi-local operators starting from the primary field. We show that the ground state averages of quasi-local operators created in this way are given by determinants.
11333779
Algebraic Representation of Correlation Functions in Integrable Spin Chains
Abstract.Taking the XXZ chain as the main example, we give a review of an algebraic representation of correlation functions in integrable spin chains obtained recently. We rewrite the previous formulas in a form which works equally well for the physically interesting homogeneous chains. We discuss also the case of quantum group invariant operators and generalization to the XYZ chain.Communicated by Vincent Rivasseau