1,712 research outputs found
GRACE/SUSY Automatic Generation of Tree Amplitudes in the Minimal Supersymmetric Standard Model
GRACE/SUSY is a program package for generating the tree-level amplitude and
evaluating the corresponding cross section of processes of the minimal
supersymmetric extension of the standard model (MSSM). The Higgs potential
adopted in the system, however, is assumed to have a more general form
indicated by the two-Higgs-doublet model. This system is an extension of GRACE
for the standard model(SM) of the electroweak and strong interactions. For a
given MSSM process the Feynman graphs and amplitudes at tree-level are
automatically created. The Monte-Carlo phase space integration by means of
BASES gives the total and differential cross sections. When combined with
SPRING, an event generator, the program package provides us with the simulation
of the SUSY particle productions.Comment: 39 page, 1 figur
Spin and spin-spin correlations in chargino pair production at future linear e+e- colliders
A possibility to measure the spin and spin-spin correlations of a chargino
pair is investigated in the process electron positron -> chargino_1
anti-chargino_1 -> (neutralino_1 quark anti-quark) (neutralino_1 quark
anti-quark) at future linear-collider energies. The total and the differential
cross sections are calculated by the GRACE system which allows for the full
spin correlation. Experimental sensitivity of the measurements are examined by
assuming the limited detector resolution, the initial state radiation and the
beam-beam effect (beamstrahlung). It is found that generally the spin-spin
correlation can only be measured with a lower sensitivity than the chargino
spin itself. The dependence of the correlation measurements on the relevant
SUSY parameters can be seen for a light sneutrino case, but the situation
becomes worse for a heavier sneutrino.Comment: 23 pages, 7 figures, 6 tables; added reference for section
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.Comment: 6 pages, Latex, ICCP
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