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

A Feynman diagram analyzer DIANA: recent development

New developments concerning the extension of the Feynman diagram analyzer DIANA are presented. We discuss new graphic facilities, application of DIANA to processes with Majorana fermions and different approaches to automation of momenta distribution.Comment: 2 pages, Latex using espcrc2.sty, 3 figures using 3 eps files. Contribution to ACAT 2002, Moscow, Russia, June 24-28, 200

Highlights of the B-Physics Landscape

The exploration of the quark-flavour sector of the Standard Model is one of the hot topics in particle physics of this decade. In these studies, which show a fruitful interplay between theory and experiment, the B-meson system offers a particularly interesting laboratory. After giving an introduction to quark-flavour mixing and CP violation as well as to the theoretical tools to deal with non-leptonic B decays, we discuss popular avenues for new physics to enter the roadmap of quark-flavour physics. This allows us to have a detailed look at the B-factory benchmark modes $B^0_d\to J/\psi K_S$, $B^0_d\to \phi K_S$ and $B^0_d\to\pi^+\pi^-$, with a particular emphasis of the impact of new physics. We then perform an analysis of the $B\to\pi K$ puzzle, which may indicate new sources of CP violation in the electroweak penguin sector, and discuss its implications for rare B and K decays. The next topic is given by $b\to d$ penguin processes, which are now starting to become accessible at the B factories, thereby representing a new territory of the B-physics landscape. Finally, we discuss the prospects for B-decay studies at the Large Hadron Collider, where the $B^0_s$-meson system plays an outstanding role.Comment: 64 pages, 19 figures, invited topical review for Journal of Physics G: Nuclear and Particle Physic

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

Sophisticated momenta mapping with DIANA

Details of recent developments of the Feynman diagram analyzer DIANA (DIagram ANAlyser) are presented. Apart from some discussion about QGRAF and new plotting features, we concentrate on a new sophisticated mechanism of momenta mapping.Comment: 4 pages, 4 Encapsulated postscript figures, LaTeX2e, uses espcrc2.sty (included). Talk given at ACAT0

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

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

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

New, Efficient and Clean Strategies to Explore CP Violation Through Neutral B Decays

We point out that decays of the kind $B_d\to D_\pm K_{S(L)}$ and $B_s\to D_\pm\eta^{(')},D_\pm\phi, ...$, where $D_+$ and $D_-$ denote the CP-even and CP-odd eigenstates of the neutral D-meson system, respectively, provide very efficient, theoretically clean determinations of the angle $\gamma$ of the unitarity triangle. In this new strategy, we use the $B^0_q$--$\bar{B^0_q}$ ($q\in\{d,s\}$) mixing phase $\phi_q$ as an input, and employ only ``untagged'' and mixing-induced CP-violating observables, which satisfy a very simple relation, allowing us to determine $\tan\gamma$. Using a plausible dynamical assumption, $\gamma$ can be fixed in an essentially unambiguous manner. The corresponding formalism can also be applied to $B_d\to D_\pm\pi^0,D_\pm\rho^0, >...$ and $B_s\to D_\pm K_{S(L)}$ decays. Although these modes appear less attractive for the extraction of $\gamma$, they provide interesting determinations of $\sin\phi_q$. In comparison with the conventional $B_d\to J/\psi K_{S(L)}$ and $B_s\to J/\psi\phi$ methods, these extractions do not suffer from any penguin uncertainties, and are theoretically cleaner by one order of magnitude.Comment: 14 pages, no figures, sign error in factorization prediction for cos(delta) corrected and numerical examples modified accordingly, conclusions unchange

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