Fukuko Yuasa

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.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.

Automatic Computation of Cross Sections in HEP

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.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.

Loop integration results using numerical extrapolation for a non-scalar integral

Abstract Loop integration results have been obtained using numerical integration and extrapolation. An extrapolation to the limit is performed with respect to a parameter in the integrand which tends to zero. Results are given for a non-scalar four-point diagram. Extensions to accommodate loop integration by existing integration packages are also discussed. These include: using previously generated partitions of the domain and roundoff error guards.

Numerical Evaluation of Feynman Integrals by a Direct Computation Method

A purely numerical method, Direct Computation Method is applied to evaluate Feynman integrals. This method is based on the combination of an efcient numerical integration and an efcient extrapolation. In addition, high-precision arithmetic and parallelization technique can be used in this method if required. We present the recent progress in development of this method and show results such as one-loop 5-point and two-loop 3-point integrals.

e+e− → bbudμ−νμ with a tt production

Abstract The cross section of e + e − → b b u d μ − ν μ process with a complete set of tree diagrams, 232 diagrams in the unitary gauge, was calculated at the energy range of s = 340−500 GeV by using GRACE system. A main contribution to the cross section comes from t t production, where t and t decay into bu d and b μ − ν μ , respectively. It was found that the interference between the diagrams with t t production and those with single- t through WW pair production amounts to 10% at the t t threshold energy region. In the energy region above twice of the top quark mass, more than 95% of the cross section comes from the t t diagrams.The cross section of

Quadpack computation of Feynman loop integrals

e^+e^- \to b \bar{b} u \bar{d} \mu^- \bar{\nu}_\mu

Numerical computation of two-loop box diagrams with masses

process with a complete set of tree diagrams, 232 diagrams in the unitary gauge, was calculated at the energy range of

Regularization and extrapolation methods for infrared divergent loop integrals

\sqrt{s}

Regularization of IR divergent loop integrals

= 340 - 500 GeV by using GRACE system. A main contribution to the cross section comes from

Transformation, reduction and extrapolation techniques for feynman loop integrals

t\bar{t}