117722201
POLARIZED CROSS-SECTIONS FOR e+ e- ---> W- lepton-sneutrino slepton+
We investigate the single W production associated with sleptons in longitudinally polarized e+e- beams. The polarized cross-sections and the angular distributions of W- are calculated for charged sleptons in left-handed and right-handed multiplets. It is shown that this process will be major background one for the standard one in the single W production at √s = 1 TeV.
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.
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.
117181820
Pair-production and Three-body Decay of the Lighter Stop at the ILC in One-loop Order in the MSSM
We have been developing a program package called GRACE/SUSY-loop which automatically calculates the MSSM amplitudes in one-loop order. We present numerical results of calculations for pair-production and three-body decay of the lighter stop ($\widetilde{t}_1$) at the International Linear Collider (ILC) using GRACE/SUSY-loop. Since the distributions of missing transverse energy (MET) depend on mass spectrum of SUSY particles, we consider two scenarios on three-body decay of $\widetilde{t}_1$. In these scenarios, both QCD and EW corrections have positive sign for decay widths and cross sections.
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.
14644136
Smirnov's integrals and the quantum Knizhnik-Zamolodchikov equation of level 0
We study the quantum Knizhnik-Zamolodchikov equation (1984) of level 0 associated with the spin 1/2 representation of Uq(SL2). We find an integral formula for solutions in the case of an arbitrary total spin and mod q mod <1. In the formula, different solutions can be obtained by taking different integral kernels with the cycle of integration being fixed.
117707944
Quantum R matrix related to the generalized Toda system: An algebraic approach
We report on some recent progress concerning the Yang-Baxter equation and related algebraic structures -the q-analogue 
 
of the universal enveloping algebra and the Hecke algebra. The results include 1) construction of trigonometric R matrices related to the vector representation of non-exceptional Lie algebras, ii) construction of representations of 
 
for 
 
, and iii) existence of R for a class of representations of 
 
.