Nonabelian Gauge Symmetry in the Causal Epstein-Glaser Approach

We present some generalizations of a recently proposed alternative approach to nonabelian gauge theories based on the causal Epstein-Glaser method in perturbative quantum field theory. Nonabelian gauge invariance is defined by a simple commutator relation in every order of perturbation theory separately using only the linear (abelian) BRS-transformations of the asymptotic fields. This condition is sufficient for the unitarity of the S-matrix in the physical subspace. We derive the most general specific coupling compatible with the conditions of nonabelian gauge invariance and normalizability. We explicitly show that the quadrilinear terms, the four-gluon-coupling and the four-ghost-coupling, are generated by our linear condition of nonabelian gauge invariance. Moreover, we work out the required generalizations for linear gauges.Comment: 32 pages, latex-file, no figure

Inclusive Rare B Decays

We review the present status of rare B decays, focusing on inclusive decay modes and their role in our search for new physics. We also briefly discuss direct CP violation in rare B decays and the rare kaon decays $K^+\to \pi^+\nu\bar{\nu}$ and $K_L \to \pi^0 \nu \bar{\nu}$, which offer complementary opportunities for precision flavour physics.Comment: 46 pages, latex, 17 figures, references adde

New Physics Search in Flavour Physics

With the running B, kaon and neutrino physics experiments, flavour physics takes centre stage within today's particle physics. We discuss the opportunities offered by these experiments in our search for new physics beyond the SM and discuss their complementarity to collider physics. We focus on rare B and kaon decays, highlighting specific observables in an exemplary mode. We also comment on the so-called B --> pi pi and B --> K pi puzzles. Moreover, we briefly discuss the restrictive role of long-distance strong interactions and some new tools such as QCD factorization and SCET to handle them.Comment: 13 pages, 9 figure

Direct CP Violation In Radiative B Decays

We discuss the role of the radiative B decays $B \to X_{s/d} \gamma$ in our search for new physics focusing on the issue of direct CP violation. We discuss in some detail a SM prediction for the CP asymmetries in inclusive $b \to s/d$ transitions, namely $\mid \Delta {\cal B}(B \to X_s \gamma) + \Delta {\cal B}(B \to X_d \gamma) \mid \sim 1 \cdot 10^{-9}$. Any measured value in significant deviation of this estimate would indicate new sources of CP violation beyond the CKM phase.Comment: latex, 8 pages, 3 figure

Interplay of Direct and Indirect Searches for New Physics

We report recent work on the interplay of collider and flavour physics regarding the search for physics beyond the Standard Model.Comment: 4 pages, based on an invited talk at PANIC11, MIT, Cambridge, USA, 24.-29.7.201

Status of SM calculations of b > s transitions

We report recent progress in SM calculations of $b \to s$ transitions. We discuss the first NNLL prediction of the $\bar B \to X_s \gamma$ branching ratio, including important additional subtleties due to non-perturbative corrections and logarithmically-enhanced cut effects, and also recent results on the inclusive mode $\bar B \to X_s \ell^+ \ell^-$. Moreover, new results on the corresponding exclusive modes are reviewed. Finally, we comment on the present status of the so-called $B \to K \pi$ puzzle in hadronic $b \to s$ transitionsComment: 10 pages, 6 figures, minor changes, published versio