15619161
Automatic Calculation of SUSY-particle Production )
AbstractWe introduce a new method to treat Majorana fermions and interactions with fermion-number violation on the GRACE system which has been developed for the automatic com-putation of the matrix elements for the processes of the standard model. Thus we haveconstructed a system for the automatic computation of cross-sections for the processes of theminimal SUSY standard model (MSSM). 1 Introduction At the theoretical point of view, it has been a promising hypothesis that there exists a symmetry calledsupersymmetry (SUSY) between bosons and fermions at the uniﬁcation-energy scale. It, however, is abroken symmetry at the electroweak-energy scale. Thus the relic of SUSY is expected to remain as a richspectrum of SUSY particles, partners of usual matter fermions, gauge bosons and Higgs scalars, namedsfermions, gauginos and higgsinos, respectively [1].The quest of these new particles has already been one of the most important pursuits to the presenthigh-energyphysics[2]. Although suchparticleshavenot yet been discovered, massesofthem areexpectedto be O(10
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
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.
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 .
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.
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.
34870247
Vertex operators in solvable lattice models
The basic properties of q‐vertex operators are formulated in the context of the Andrews–Baxter–Forrester (ABF) series, as an example of face interaction models, the q‐difference equations satisfied by their correlation functions are derived, and their connection with representation theory established. The q‐difference equations of the Kashiwara–Miwa (KM) series are discussed as an example of edge interaction models. Next, the Ising model, the simplest special case of both ABF and KM series, is studied in more detail using the Jordan–Wigner fermions. In particular, all matrix elements of vertex operators are calculated.
122556189
Introduction to the {Yang-Baxter} Equation
15236365
QUANTUM AFFINE SYMMETRY IN VERTEX MODELS
We study the higher spin analogs of the six-vertex model on the basis of its symmetry under the quantum affine algebra . Using the method developed recently for the XXZ spin chain, we formulate the space of states, transfer matrix, vacuum, creation/ annihilation operators of particles, and local operators, purely in the language of representation theory. We find that, regardless of the level of the representation involved, the particles have spin 1/2, and that the n-particle space has an RSOS type structure rather than a simple tensor product of the one-particle space. This agrees with the picture proposed earlier by Reshetikhin.
2947742
Difference equations in spin chains with a boundary
Correlation functions and form factors in vertex models or spin chains are known to satisfy certain difference equations called the quantum Knizhnik-Zamolodchikov equations. We find similar difference equations for the case of semi-infinite spin chain systems with integrable boundary conditions. We derive these equations using the properties of the vertex operators and the boundary vacuum state, or alternatively through corner transfer matrix arguments for the eight-vertex model with a boundary. The spontaneous boundary magnetization is found by solving such difference equations. The boundary S-matrix is also proposed and compared, in the sine-Gordon limit, with Ghoshal-Zamolodchikov's result. The axioms satisfied by the form factors in the boundary theory are formulated.