DIANA and selected applications

New developments concerning the extension of the Feynman diagram analyzer DIANA are presented. We discuss new graphics facilities, different approaches to automation of momenta distribution and parallel processing facilities. Furthermore applications to $t\bar t$ production and Bhabha scattering are shortly discussed.Comment: Latex, 5 pages, 4 eps figures, uses included npb.sty, presented by at RADCOR and Loops and Legs 2002 8-13 September 2002, in Kloster Banz, German

Calculation of Feynman diagrams with zero mass threshold from their small momentum expansion

A method of calculating Feynman diagrams from their small momentum expansion [1] is extended to diagrams with zero mass thresholds. We start from the asymptotic expansion in large masses [2] (applied to the case when all $M_i^2$ are large compared to all momenta squared). Using dimensional regularization, a finite result is obtained in terms of powers of logarithms (describing the zero-threshold singularity) times power series in the momentum squared. Surprisingly, these latter ones represent functions, which not only have the expected physical `second threshold' but have a branchcut singularity as well below threshold at a mirror position. These can be understood as pseudothresholds corresponding to solutions of the Landau equations. In the spacelike region the imaginary parts from the various contributions cancel. For the two-loop examples with one mass $M$, in the timelike region for $q^2 \approx M^2$ we obtain approximations of high precision. This will be of relevance in particular for the calculation of the decay $Z \to b\bar{b}$ in the $m_b=0$ approximation.Comment: 17 pages with figures and tables, PostScript file gzip'ed and uuencode

Steps towards full two-loop calculations for 2 fermion to 2 fermion processes: running versus pole masses schemes

Recent progress in the calculation of the two-loop on-shell mass counterterms within the electroweak Standard Model (SM) for the massive particles are discussed. We are in progress of developing a package for full two-loop SM calculations of 2 -> 2 fermion processes, with emphasis on the analytical approach where feasible. The complete two-loop on-shell renormalization is implemented. Substantial progress has been made in calculating the master integrals. We are able to compute in an efficient and stable manner up to a few thousands of diagrams of very complex mass structure.Comment: 4 pages, 1 style file. To appear in the proceedings of 9th International Workshop on Advanced Computing and Analysis Techniques in Physics Research (ACAT 03), Tsukuba, Japan, 1-5 Dec 200

Parallel Computation of Feynman diagrams with DIANA

Co-operation of the Feynman DIagram ANAlyzer (DIANA) with the underlying operational system (UNIX) is presented. We discuss operators to run external commands and a recent development of parallel processing facilities and an extension in the spirit of a component model.Comment: 23 pages, Latex using psfig, epsf and alltt, 3 figure

Some methods to evaluate complicated Feynman integrals

I discuss a progress in calculations of Feynman integrals based on the Gegenbauer Polynomial Technique and the Differential Equation Method.Comment: 2 pages, 1 figure, latex. Talk presented at the 8th International Workshop on Advanced Computing and Analysis Techniques in Physics Research (ACAT 2002), Moscow, Russia, June 200

Penguin Topologies, Rescattering Effects and Penguin Hunting with Bu,d→KKˉB_{u,d}\to K\bar{K} and B±→π±KB^\pm\to\pi^\pm K

In the recent literature, constraints on the CKM angle $\gamma$ arising from the branching ratios for $B^\pm\to\pi^\pm K$ and $B_d\to\pi^\mp K^\pm$ decays received a lot of attention. An important theoretical limitation of the accuracy of these bounds is due to rescattering effects, such as $B^+\to\{\pi^0K^+\}\to\pi^+K^0$. We point out that these processes are related to penguin topologies with internal up quark exchanges and derive SU(2) isospin relations among the $B^+\to\pi^+K^0$ and $B_d^0\to\pi^-K^+$ decay amplitudes by defining ``tree'' and ``penguin'' amplitudes in a proper way, allowing the derivation of generalized bounds on the CKM angle $\gamma$. We propose strategies to obtain insights into the dynamics of penguin processes with the help of the decays $B_{u,d}\to K\bar{K}$ and $B^\pm\to\pi^\pm K$, derive a relation among the direct CP-violating asymmetries arising in these modes, and emphasize that rescattering effects can be included in the generalized bounds on $\gamma$ completely this way. Moreover, we have a brief look at the impact of new physics.Comment: Some mistakes in the equations have been corrected, conclusions have been changed slightly. The complete paper, including figures, is also available via anonymous ftp at ftp://ttpux2.physik.uni-karlsruhe.de/, or via www at http://www-ttp.physik.uni-karlsruhe.de/cgi-bin/preprints

Régiók, határok és hálózatok [=Regions, Borders and Networks]

Regons, Borders and Networks The title of the conference "Borders and Regions" was considered by the majority of the lecturers as problems of a region at the border of a larger region (country, European Union). This lecture deals rather with the relation of a region to its own border: sets out the main functions of the frontiers of a region and concludes how certain networks can help to fulfil the same tasks. Nowadays both in strict sense and figuratively there is a shift from using sharp administrative borders towards creating indistinct frontiers. Sharp spatial borders become concentration of tension rather then solving problems (iron curtain, US—Mexican border etc.). As an analogy we can also refer to the general shift from regulation with sharp administrative limits towards market-type regulation with softer frontiers (in economy, environmental protection etc.). Over the roles supplied by a frontier zone (buffer, filter and barrier) it is a characteristic spatial structure within the region that has a chance to select the external effects arriving to the region. The physical networks that are spatial imprints of the existing relation systems have four possible roles as internal provision, external accessibility, to assure through-cut and of avoiding a region. The condition of the good operation of a region is the good local provision, that is the existence of appropriate internal networks. Out of its existence the pattern of the structure is also determining: creating appropriate internal transport network in a region it is an important target to built out multilateral net structures so, that a similar provisional position be able to decrease (and not increase) the differences originated from the position of there different localities. The measure of good accessibility is the multilaterality and multidirectionality of relations. There are two important levels of accessibility links to be distinguished: the direct main, large-scale axes and the transborder extension of the subordinated internal provision networks. In case of similarly developed linked regions, we can expect that the advantages due to the improvement of the relation will also be symmetrical between the regions. Improving accessibility between developed and less developed regions, it is not so clear, that the result is similar: we also have to take into account whether the internal structure in the underdeveloped side able to develop at a measure needed by externally controlled changes. In order to defend and develop the internal structure, the through traffic crossing the region has to be led with minimised harmfulness and with minimised troubling of internal relations. We have to learn, that it is impossible to eliminate through traffic, but on the other side it is not at all an aim to attract more of it into the region. With the metaphors Island, Basin and Crossroad we try to describe the relation between a region and its environs. The Island represents the isolated region without external relations. A Basin disposes with clearly interpretable frontiers, while there are gates along this frontier that are able to both let and filter the inflow. In the same time the internal structure is also able to select: there are incoming elemen[ easily melting into the structure, while other elements are not. The Crossroad is a part of the space where the internal structures have no role or importance; everything serves those arriving, everything is determined by external structures. By forming the transport network we can influence the endowments of a region. In connection with that task now in Hungary (and in Eastern Central Europe) we just have to strengthen the Basin-characteristics and as we are able we have to decrease the danger to be involved into a Crossroad role. Understanding such role of the networks gives us a possibility that the networks, in frame of a conscious development policy be ready to take over a part from the role of the frontiers and by that development a functional harmony could be created between the tasks of the frontiers and the internal structures

A path to filled archives - how bumpy is it going to be?

The need for data capturing during the data creation process becomes increasingly important in regard to mandatory data submissions in addition to article submissio