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

Flavour data constraints on new physics and SuperIso

We discuss the implications of B_s -> mu+mu- and B -> K*mu+mu- decays in the context of indirect searches for new physics, emphasising the new LHCb results. In particular, we derive the consequences of the MFV hypothesis and discuss the importance of the MFV predictions. The impact of the recent LHCb measurements in the context of the MSSM will also be addressed, and the SuperIso program will be briefly described.Comment: 7 pages, 4 figures, contribution to the ICHEP 2012 Conference proceedings, 4-11 July 2012, Melbourne, Australi

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

Signs for new physics in the recent LHCb data?

We comment on some tensions with the Standard Model predictions in the recent LHCb data.Comment: 6 pages, 6 figures. Based on talks given at the Fifth Workshop on Theory, Phenomenology and Experiments in Flavour Physics, Capri, 23-25 May 2014 and at the FPCP 2014 conference on Flavor Physics and CP Violation, Marseille, 25-30 May 201

Comments on the Gauge Fixed BRST Cohomology and the Quantum Noether Method

We discuss in detail the relation between the gauge fixed and gauge invariant BRST cohomology. We showed previously that in certain gauges some cohomology classes of the gauge-fixed BRST differential do not correspond to gauge invariant observables. We now show that in addition ``accidental'' conserved currents may appear. These correspond one-to-one to observables that become trivial in this gauge. We explicitly show how the gauge-fixed BRST cohomology appears in the context of the Quantum Noether Method.Comment: 24 pages, example section improved, short version without background material will appear in Physics Letters

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

Indirect search for supersymmetry in rare B decays

QCD corrections to the gluino induced contribution to b --> s gamma are shown to be important in order to extract reliable bounds on the off-diagonal elements of the squark mass matrices.Comment: 4 pages including 2 postscript figure